Stumbles and Will Not Up Shift

Tiny
JDBKNIFE
  • MEMBER
  • 2003 CHRYSLER PT CRUISER
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I. My wife has an 03 PT Cruiser we bought new and that she absolutely loves, which means I have an ongoing problem problem. A while back the check engine light came on and it began stumbling under acceleration. It also got so that it would not up shift to the next gear at more than about 1/4 throttle until we let up on it then it shifted normally.

So.I did the "key dance" to get the codes and found the problem to be plugs. I replaced the plugs and wires while I was at it, started it, took it for a test and all was well. It accelerate smoothly and even shifted under heavy acceleration as it should have. She drove it a few times, the check engine light went out and all was well.

About a week or so later, we got in it to go somewhere and I noticed it was surging under acceleration. We got onto the interstate and up to speed, 70 MPH or so, for about 5 miles and the car began to sputter and slow down to the point that I thought it had died and pulled over to the emergency lane. It hadn't so we did a U-turn to get another vehicle. The car actually ran fine back to the house.

SO.I did the key dance again and this time there were NO CODES that showed up. So she has continued to drive it with no more problems. Until today, she complained again so I test drove it. It seems to be surging or stuttering at any constant speed. It accelerates well and normally, but surges at a constant throttle position. And the problem of not up shifting under heavy acceleration has returned. As long as you baby it. It stumbles, but shifts normally. Push it and it sounds like it will sling the hamsters right out of their treadmills before it would shift, but the miss goes away.

SO. Again I do the key dance and STILL no codes.

Have you encountered anything like this? I've considered everything from O2 sensors to plugged up Cat converter, but I THINK those things would throw a code. I'm kind of at a lose as to how to proceed. It IS a 11 year old car with 150,000 miles after all. However, we are in a position where we don't want to buy a new car for a few more months. ANY help would be a BIG help. Thank you.
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Sunday, May 4th, 2014 AT 5:44 PM

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Tiny
CARADIODOC
  • EXPERT
What you described is typical of a plugged or collapsing pickup screen in the fuel tank. If you have a fuel pressure regulator on the fuel rail on the engine, the problem will be worst when the largest volume of fuel is being pumped, which is during coasting. The screen will usually stretch out again after the engine has been off a few minutes, but the problem will act up again within a few miles.

The fastest way to verify this is to drive with a fuel pressure gauge attached and hooked under the wiper arm. Since the fuel supply system isn't monitored, no fault codes will be set related to it.
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Sunday, May 4th, 2014 AT 6:13 PM
Tiny
JDBKNIFE
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Thanks for the quick response Caradiodoc.

That brings up something I didn't think about. If the pickup screen is mostly plugged or clogged, which in an 03 car burning ethanol "enhanced" fuel for 10 plus years, it is very conceivable that rust caused by the excess moisture ethanol attracts could do that. Is it possible the fuel filter could be the problem as well?

I just assumed that ANY fuel flow problems to the injectors would be monitored and throw a code. Even an intermittent problem. And I surely didn't consider that the flow could alter the filtering devices since most modern fuel pumps maintain a constant fuel pressure.

Where am I going wrong in my thinking?

And thanks again for the quick response. If we have to replace the little car now, we will have to trade it in. If I can keep it going for a few more months, I get to keep it and turn it into a toy. The wife loves it and it's the only way she will let me turn it into a rear wheel drive hot rod. ; )
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Monday, May 5th, 2014 AT 9:01 AM
Tiny
JDBKNIFE
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Oh, and why would that cause the car not to up shift normally under heavy acceleration when it appears to be running well under heavy acceleration? Just a bit more than a little confusing for an old school hotroder?

But I WILL follow your suggestion and check the fuel pressure as soon as possible.

Thanks
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Monday, May 5th, 2014 AT 10:45 AM
Tiny
CARADIODOC
  • EXPERT
I have to admit that I don't know which fuel system you have and I can't find the information from my normal sources. At issue is where the pressure regulator lives. My understanding is if it's in the tank, you do have constant pressure all the time, and the Engine Computer is programmed for that.

When the regulator is on the fuel rail on the engine, there's a vacuum hose going to it. That causes it to vary the fuel pressure according to manifold vacuum. You have two forces acting on a molecule of fuel sitting at the tip of the injector. Think of a person about to parachute out of a perfectly good airplane. There's two forces working on him too. The suction of the air flow, and the big guy behind him pushing him out! If the plane goes faster, there's more suction so the fellow pushing him doesn't have to push so hard. In the injector, when you're coasting, vacuum goes way up and pulls really hard on the fuel to pull it out of the injector. If fuel pressure remained constant, you'd have a seriously-rich condition during coasting, and lots of wasted fuel and excessive emissions. To prevent that, thanks to the vacuum hose hooked to the regulator, fuel pressure drops down a good ten or fifteen pounds.

This is where the secret part comes in. With the pressure regulator relaxed to maintain a lower pressure, it is easier for the fuel to get through it and go back to the tank through the return hose. THAT'S why fuel VOLUME goes way up during coasting. The volume going into the engine goes way down, but the volume flowing through the pickup screen and back to the tank goes way up. That's why a plugged screen will cause stalling when coasting, but not during acceleration or cruising. This has happened twice on my old rusty trusty '88 Grand Caravan. The first time it took me four hours to nurse it through all the road construction in Minneapolis, but once I made it to the open highway, it ran fine the next four hours to home.

The second time, which was less than a year ago, since I already knew what to suspect, I disconnected the vacuum hose from the regulator and plugged it, and the stalling stopped occurring. That is a dandy clue IF you already know what to suspect.

As far as the fuel filter, I have never solved a problem on a Chrysler product by replacing it. That can't be said for any other vehicle brand that I'm aware of, but at 253,000 miles, my filter would have still been original if it hadn't rusted through and started leaking.
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Monday, May 5th, 2014 AT 8:30 PM
Tiny
JDBKNIFE
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Ok, ok, can you see, am I bleeding from the ears? LOL

Just kidding brother. That was pretty good. I think I actually understand it. The principles of vacuum part I get easy enough. Been putting vacuum canisters on hotrods with power brakes for years. So how it works on the regulator, I get.

That returning fuel to the pickup screen is kind of alchemy to me at the moment. But I suspect all will be revealed once I take the tank off and pull the fuel pump to replace the screen or pump or whatever I can/must to fix this. And it sounds like that is going to be the likely ultimate outcome from what you are suggesting.

What I am gathering is that Mopar, in a moment of sheer engineering brilliance, decided to run return fuel back through the same "pickup" porting for the fuel pump as is used to supply the fuel pump and it is that which is causing the restriction of the screen to become magnified at part throttle.

Seriously, has anyone got an aspirin?

Thanks and I'm going to see if I can find a vacuum hose going to a regulator for the injectors, pull and plug it and see how that effects the problem. I don't know, but I'd say you are right and there is one on the fuel rail of the PT Cruisers. There's flippin' little vacuum hoses running everywhere under the hood of that thing. LOL

But that would be a good quick check until I can get a pressure gauge installed and test it on the road as you suggested.

Thanks a ton Caradiodoc. That was a big help. Makes my brain hurt, but a big help. ; )
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Monday, May 5th, 2014 AT 9:41 PM
Tiny
CARADIODOC
  • EXPERT
Actually, the return system isn't that involved. There's a small tank, or pot, in the middle of the gas tank. The pump and pickup screen sit inside that little tank. It only holds about a quart of fuel, but because it's so small, there's always fuel next to the screen when you go around a corner with an eighth tank of gas. The fuel can't run away from the pickup.

The return fuel dumps into that tank to keep it full. That part is easy to understand, but I just put a new tank and pump in my van a few weeks ago, and I had to dig out the service manual to read the description of operation, and I find it difficult to believe and understand. It said the flow of that fuel along the bottom of the little tank creates a low pressure area like the venturi in a carburetor, and that low pressure draws in fuel from the main tank. I didn't autopsy my old tank enough to see how that is designed, but it must work. Also, if you run out of gas, then pour in one gallon, you would think the filler tube would dump it into that little tank, but it can't. Mine dumps the fuel in the middle of the gas tank but a few inches in front of the little tank. How is it then that the pump will pump fuel and the engine will start after adding just one gallon? There's no flow from the return line to create that low pressure area to draw the fuel into the little tank. That must work too though, because otherwise you'd have to almost fill the tank to get the fuel level high enough to flow into the little tank.
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Monday, May 5th, 2014 AT 10:31 PM
Tiny
JDBKNIFE
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ALL, very good questions brother. The pictures I've seen of the fuel pump assembly in the Cruiser's tank just shows the little round, screen covered inlet in the very bottom of the "slosh" tank. Like you say, unless there is a hole at the top of the little tank, I don't even see how a gallon of fuel spread across the bottom of the tank could overcome the air pressure and pass into the small tank period. Much less be picked up and pumped. And if there IS a hole, wouldn't that defeat the purpose of the thing and create the equivalent of a hole in the fuel pickup line?

The ONLY thing I can imagine is that the action of the pump, IF it can pump air, forcing the air through the fuel system creates a low pressure in the little slosh tank and allows the fuel to push up into it. BUT, that would mean that the volume of the fuel system, lines, fuel rail and the rest are equal in volume to the volume of the little tank?

Oh, man. Anyone got an aspirin? LOL

As you say, THAT is a LOT of ifs to be engineering into something, on purpose, that SHOULD be pretty straight forward and simple. Heck, racing fuel tanks ain't that freakin' complicated! ; )

At any rate, I will let you know what I find. I've pretty much made up my mind I'm going to pull the thing out this weekend and have a look, clean the tank and screen and try that. I may even install an access panel under the back seat while I'm at it in case I end up needing to replace the fuel pump it's self. Cause I'm just lazy like that. ; )

I really do appreciate you sticking with me on this brother. It's really informative and helpful in my thinking this through.

THANKS. Hopefully once this is solved, it will allow you to help someone else down the road.
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Wednesday, May 7th, 2014 AT 10:40 AM
Tiny
JDBKNIFE
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Ok Caradiodoc, I removed the fuel pump this weekend. And MAN was that fun for a wore out ol' fat man. But I removed, inspected and cleaned what I could. Didn't find anything really obvious beside something that looked like ground black plastic in the bottom of that slosh tank.

The pickup screen inside that tank didn't APPEAR to be clogged or collapsed. Of course that doesn't mean anything given how fine the mesh is. I did use some air at low pressure to blow it out some just in case.

After putting it back together, it spun over about 2 times and fired right up. Idled smooth, so I cut it off and restarted it 3 more times before I let it idle till warm. All went perfectly, it got warm, the RPMs dropped slightly after running a couple minutes and remained steady.

So, the test drive. It doesn't seem to be missing/stuttering any more, but it STILL is down on power and instead of a quick surge at part throttle, the RPMs go up and down like you are slowly pumping the peddle slightly. All in all, the ONLY improvement is that the quick stutter seems to have gone and the speed/frequency of the surges seems to have slowed and become more pronounced. Huh? Weird!

By the way, STILL no codes when I do the key dance. And from your advice and other research I've done, the fuel pump is one of the few systems that is not monitored by the fault system. So, that makes sense. From what I've found, a bad pump/regulator may cause a false code for other systems such as the O2 sensors, but fuel pressure isn't monitored. Don't understand why not, but then I'm just an ol' redneck, not an automotive engineer. ; )

Long and short of it, unless you have any other suggestions based on my description, I'm going to order a fuel filter and replace it next weekend. IF it doesn't leave my wife stranded before then. If so, It will be sooner since she insist on driving it. ; )

Any further feedback you could give me would be greatly appreciated brother. The fact that my playing with the pump changed the way it drives without changing the "no code" circumstance leads me to believe there's no question that's the problem. But then, I'm subject to jumping to conclusions according to my wife. ; )

Thanks again Caradiodoc.
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Monday, May 12th, 2014 AT 8:17 AM
Tiny
CARADIODOC
  • EXPERT
The only other words of wisdom I can offer are, first of all, if you have a fuel filter along the right frame rail, I have never seen a new one solve a running problem on a Chrysler product. The one on my '88 Grand Caravan daily driver would still be original if it hadn't started leaking from rust many years ago.

Second, my first strainer in the tank was seriously plugged with a reddish-colored mud over ten years ago. The second one, last summer, looked perfectly fine but a new one solved the stalling due to low fuel pressure after prolonged pulling a tandem axle enclosed trailer that's bigger than the van. Besides getting plugged with microscopic debris and mold that feeds on the ethanol in gas today, they can collapse and block the opening in the pickup tube. That usually doesn't show up for five to fifteen miles, then it will stretch back out after sitting with the engine off for about five miles.
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Wednesday, May 14th, 2014 AT 6:08 PM
Tiny
JDBKNIFE
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Well, I changed the fuel filter, took her for a test drive and no joy. SAME DANG THING.

I'm kind of at a loss.

By the way, not sure it makes any difference, but I wrote that it's an '03 Cruiser and it's actually an '06. Don't know why I got that brain cramp, but I'm an ol' guy. So there IS that. LOL

At any rate, I'm lost. I was just sure the new pump would fix the problem. Especially after cleaning the old one last weekend had an effect on the stumbling. But the new one is still exhibiting that slow surge and loss of power at part throttle and failure to shift under heavy acceleration. And it still idles perfectly.

If I didn't know better, I'd say it was a computer problem. Actually, I DON'T know better. I don't have a clue what kinds of nightmares control modules can cause. And besides, I did the key dance again and still no fault code.

Now I'm wondering if the TPS or something is going bad and just not throwing a code. Yep, I'm grasping at straws. ; )

Caradiodoc, my friend. I've been building hot rods under shade trees for nearly 50 years. I've been buying new cars for nearly 40 years and the last mechanic, dealer or otherwise, I took a car to was a fuel injected 1972 Volkswagen wagon because I just didn't have time to spend adjusting the valves every time I changed the oil.

My friend, I am just about ready to break that string. GRRRRR!

I don't THINK it has a filter on the frame rail. Don't remember seeing one, but I'll check and change that if it does. As you say, with this stinking ethanol eating every rubber part on anything built before 2011, If It's there, it's probably FOBARed.

I also think I'll get a can of starting fluid and check for vacuum leaks, just to ease my mind since this started not long after I changed the plugs and wires. Don't see how it could cause this since vacuum leaks normally shows up at idle, but as I said, I'm grasping at straws. LOL

Anyway, that's the update. Still no joy!

And again, thanks for hanging with me on this. We live WAY out in the country and finding someone to bounce ideas off of is kind of, well. There just ain't nobody that doesn't tell me to shut up and take out the garbage. LOL

Thanks,

JD
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Friday, May 16th, 2014 AT 11:15 PM
Tiny
CARADIODOC
  • EXPERT
If I didn't mention it already, other than on diesels, you'll never solve a running problem on a Chrysler product by replacing the fuel filter on the frame rail. I don't know if that applies to the newer ones with the filter in the tank, but I suspect they did that, in part, because replacement really isn't necessary.

There's two things that can be done to try to find this problem. One is to attach a fuel pressure gauge and clip it to the radio antenna so you can watch the pressure when the problem occurs. I did that on my '88 Grand Caravan for a year and a half when chasing a real intermittent problem. I've never done this on a vehicle with the pressure regulator inside the gas tank, so I don't know what they will do, but with the regulator on the fuel rail on the engine, the pressure goes up during acceleration when intake vacuum goes down. That's to keep the difference in the two forces acting on the fuel at the injector tips equal at all times, and is why there's a vacuum hose attached to the regulator.

The second thing requires a scanner with record capabilities. You press the "record" button when the problem occurs. A few seconds of data is recorded that can be played back slowly later while watching the sensor readings the computer acts on, like throttle position sensor and coolant temperature sensor, and the results of those actions, like oxygen sensor readings. Simple fault code readers won't be able to do that. You'll likely have to find a mechanic with a scanner.
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Saturday, May 17th, 2014 AT 7:18 PM
Tiny
JDBKNIFE
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That's a good idea Car. As I said, we live a LONG way from anything, but I'll do some calling and see if the nearest Autozone or something has a reader with record feature and would be willing to help.

SUREly that would find the problem if it's something that's so intermittent the factory fault system misses it.

Although, I don't see how the factory fault systems isn't getting it given that the surge it has now is a slow, drawn out up and down surge at part throttle.

Oh, and it doesn't have a fuel filter on the frame rail that I can find. So I suspect the strainer system in the slosh tank on the fuel pump is what they call a filter. ; )

I know I'm loosing patients. Other than having to hear it from my wife for not getting it fixed before it left her stranded, I wish the dang thing would just go on and break so I could find it. LOL
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Sunday, May 18th, 2014 AT 1:20 PM
Tiny
CARADIODOC
  • EXPERT
Actually, the fault detection system is real effective and is much easier to work with than on some other brands. The first part of it has to do with sensor voltages going out of range. For example, the throttle position sensor is fed with 5.0 volts and ground. Due to mechanical stops, the signal voltage will always be between 0.5 and 4.5 volts. The only way it can go to 0.0 volts or 5.0 volts is if there's a break in a wire, connection, or inside the sensor, and that's what triggers the fault code. If the broken connection is intermittent, the Engine Computer will detect a break that lasts for just a few milliseconds, while all scanners and especially all digital voltmeters respond much too slowly to show those.

The clinker here is when a sensor sends a wrong signal voltage but it's within the acceptable range. That isn't likely to happen to a throttle position sensor because it's a simple mechanical device, but a MAP sensor has a lot of circuitry inside it so it is very possible for it to send, ... Lets say 2.2 volts, which is within the acceptable range of 0.5 to 4.5 volts, when it is supposed to be 2.4 volts. That 0.2 volt error will result in a major miscalculation on the required amount of fuel, but it won't set a code because 2.2 volts is an acceptable value.

The next part of fault detection involves operating conditions that would be almost impossible to determine yourself by watching the readings on the scanner. A perfect example would be, "running too lean too long". In that case the oxygen sensor is obviously working as it is supposed to, but the exhaust gas is not switching between rich and lean fast enough. Normal is about twice per second, but you may see it stay in one state for much longer on a scanner. You can't tell exactly when this type of code will be set. One instance typically won't do it. The computer decides when the exhaust gas is staying in one state too much, and that can take hours or days.

The third part of fault detection was added with all '96 and newer vehicles. Now misfires can be detected by the slowing of the rotational speed of the crankshaft, (which is what we feel when we feel that misfire). The computer knows which cylinder is responsible, but it takes a certain number of misfires within a given amount of time to set a code. Along with this, the fuel supply system is monitored for leaks in the vapor recovery system. This is why the Check Engine light will turn on and a code will be set if you leave the gas cap loose.

The nice thing with Chrysler's system is when the Check Engine light turns on, there WILL be a fault code. Some cars, GMs in particular, use what they call "pending codes". Those relate to things the computer is watching in preparation for setting a code, but the problem isn't quite bad enough yet. Sometimes those pending codes can give you an idea of where to look, if you can read them, but often there is no code, ... Just the phantom Check Engine light that turns off before you get to the shop, and you have no idea why it came on.

Don't know if that will help or not, but it might explain why there is no code being set. The fuel supply system is not monitored as far as pressure is concerned, so you won't get a code related to that, but you could get a code related to the RESULT of low or high pressure. Those would be running too lean or too rich.
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Monday, May 19th, 2014 AT 2:11 PM
Tiny
JDBKNIFE
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Yep, GREAT explanation of VERY confusing systems for an ol' shade tree mechanic to get, Car Doc.

Doc, I FINALLY got it on a diagnosis machine. He did all the standing checks, used his little tablet to play with the idle, check ALL the systems and told me what I already suspect. I had unhooked the battery the AC need servicing and there were NO CODES. LOL

So, he and his computer took a test drive. Again, NO engine codes. The way it was acting made him suspect it's a transmission problem. So he stopped and reset it to quick learn and drove it again recording the data points. The ONLY code he got at all for ANYthing that seemed out of place was that it SAYS that the overdrive clutch is engaged all the time? What?

Anyway, he said that all he could think of was that MAYbe the overdrive clutches have stuck together from carbon build up or something. Kind of like the clutch packs in Ford rear ends tend to do and cause that infamous clunk going around corners. So, he sent me up the road to a friend who has 45 years experience in transmission repair.

By the way, the mechanic spent an hour an a half tinkering with the little car and didn't charge me a DIME. And I TRIED to get him to let me pay him for his time. He said, "Nope, I don't charge if I can't fix it." Cool to find principled mechanics these days. ; )

ANYway, I went up to the transmission shop and the owner took her for a drive. He came back and said, "Their ain't SHITE wrong with that transmission."

He's kind of a surly ol' boy and shite ain't the exact word he used, but you get the point. LOL

Anyway, he said I've seen this with a LOT of different cars and it's the catalytic converter. WHICH, I've gotta say is something I've suspected from the start. He didn't even bother hooking it up to his computer. He said flat out, replace the converter and it will run like a Deer. As in John Deer of course. Did I mention I'm in a rural area?

At any rate, I asked if it wasn't trowing a code because the O2 sensor was working fine and it was just a software conflict between the actual air flow and the computed air flow that's causing all these symptoms, to which he said, "Yep, I've seen it a bunch." Then he repeated, "Replace the converter and it'll run like a Deer."

A question for you Car Doc. Does that make sense to you? As I said, I've suspected the converter from the beginning, but this computer stuff is WAY above my pay grade. I didn't and STILL DON'T have a clue how all this computer stuff interacts and what symptoms can be induced by the computer module because of faulty readings.

What say you Doc? I hate to pay 300 bucks for a converter and end up with a trashed transmission to deal with anyway. Ya know?

And thanks again for hanging with me on this. I'm sure you've got better things to do, so I really do appreciate your feedback!
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Thursday, May 22nd, 2014 AT 10:02 AM
Tiny
CARADIODOC
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I can't argue with any expert on driveability issues because that's not one of my specialty areas, but I can share how the system is supposed to work. The Engine Computer varies the fuel / air mixture from too rich to too lean about twice per second. During the lean times, the extra unburned oxygen gets stored in the catalyst. During the rich times, the unburned fuel vapors mix with the oxygen and burn off resulting in basically carbon dioxide and water vapor as the exhaust. When the catalytic converter is working properly, the oxygen sensor after it will detect a slightly lean condition for a fairly long time, as in a minute or more, then a slightly rich condition for a long time. The computer watches how long it takes for that switching rate to occur. The "downstream" O2 sensor switches very slowly and the "upstream" one switches very quickly. That's how the computer knows the converter is doing its job.

Based on the voltage readings from the upstream O2 sensor, the computer adjusts the mixture so the average is a perfect 14.7 / 1. That is the only oxygen sensor involved in fuel metering. Even when it has a bad enough problem that it doesn't develop the proper signal voltage, it has very little effect on engine performance. It affects emissions and can affect fuel mileage, but usually the engine will run fine. The rear sensor has no affect on engine performance at all, and no affect on fuel metering calculations. Its only function is to monitor the efficiency of the catalytic converter.

Two things can happen to the converter. It can become plugged, usually from overheating caused by some other defect that resulted in too much raw fuel going into the exhaust system, or the catalyst stops working by becoming coated with a contaminant so it can't store oxygen. You can tell the severity of a diagnostic fault code by how the Check Engine light acts, and the most severe is when it's flashing. That means too much raw fuel is going into the exhaust and will overheat and melt the catalyst. Typically it turns into a big rock that is not porous enough for the exhaust gas to pass through freely. That usually results in easy starting, but then very low power, almost non-existent acceleration, and an unusual hiss from the tail pipe instead of the normal "putt-putt" sound. The engine often idles fine, and if you can drive the car, the engine overheats easily. This type of problem is not intermittent. The test for it involves drilling a small hole in the exhaust pipe, then inserting a pressure gauge to measure the back pressure. A little is normal. I don't know what is considered excessive, but it seems to me I heard once that two pounds is too much.

When the catalyst stops working, the exhaust can still flow freely through it so there is usually no running problem. Any stumbles or hesitations are likely due to the computer causing changes to the fuel metering calculations in an attempt to clean up the emissions. As the efficiency of the converter goes down, it has less affect on the composition of the exhaust gas so what comes out starts to resemble what went in. When no change at all takes place in the exhaust gas within the converter, what goes in and what comes out will be exactly the same, so the downstream oxygen sensor will switch between rich and lean at exactly the same rate as the upstream sensor. It takes some time for the downstream sensor to go from switching once per minute or so to switching twice per second like the upstream sensor. There is a magic number programmed in that must be met to set the fault code for "catalytic converter efficiency". It doesn't have to reach the same twice per second of the upstream sensor. If I had to guess, I'd suggest the code might be set when the downstream sensor starts switching at maybe once every five seconds for a brief spurt, or perhaps once every ten seconds steadily. Those are just estimates to illustrate how the computer determines when to set a code.

There's a very high percentage of fault codes that relate solely to things that could increase emissions while having no negative effect on engine performance. To affect performance, the converter would have to be plugged. I'm not convinced the symptoms you described would be caused by the converter, but I certainly won't argue against it. With such an expensive part, I'd want to see some evidence on a scanner to support that argument before I spent that much money.
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Thursday, May 22nd, 2014 AT 5:29 PM
Tiny
JDBKNIFE
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Yeah, I was afraid you'd say that Doc. I've told my wife from the beginning that I thought it was an air in or air out problem. As in intake leak or plugged converter problem. So the ol' boy's proclamation about the converter fitted right in with what I wanted to believe. And while your description, "That usually results in easy starting, but then very low power, almost non-existent acceleration, and an unusual hiss from the tail pipe instead of the normal "putt-putt" sound. The engine often idles fine, and if you can drive the car, the engine overheats easily." Fits what's going on almost exactly, I have NOT notice a change in exhaust note OR any overheating yet.

Of course, the fuel mileage has also gone down by at least a couple miles per gallon. So it IS running rich. I don't know about the Chrysler's systems, but Fords would feed rich when the engine got hot to cool them down. Had a little V6 Ranger that the impeller had come completely off the water pump and I didn't know it for a WEEK! LOL

But if they work the same, it could be running hotter and the computer is running it rich trying to make up for it, I guess?

At any rate, where does that leave me? The ONLY thing out of the 1 1/2 hour scan fest that the ASE mechanic found was the code saying the overdrive clutch is engaged all the time. He says the engine is perfect and the only thing he found was the overdrive clutch.

But I've gotta say, I have built and rebuilt many automatic transmissions over the years. It's all I've run in my hotrods. I learned a long time ago how to tell excessive wear on transmission parts by the smell of the fluid. I know, I know, sounds crazy, but I have yet to miss catching a problem just by sniffing the oil. The oil smells fine. Not even a hint of burnt fluid smell and It's clean as the day it went in. Almost suspiciously so.

And I swear brother, it just flat doesn't feel like transmission slip. If it IS the overdrive clutch causing it, it's causing the computer to go apoplectic, not the transmission it's self. Oh man. I'm back to, "can you see if I'm bleeding from the ears, " again. LOL

Let me ask ya. In full size Fords, there is that problem with the clutches sticking together in the rear ends. So much so that Ford came out with a treatment for it. I think it's called Friction Ease if I remember right. What do you suppose would happen if it actually were the overdrive clutch pack stuck together and I put a can of that in the transmission? Wonder if it would be safe for a transmission? OR do you know of anything else that's safe that would remove the carbon buildup I could try?

Your right about the expense of a converter as a first resort. I jumped the gun on the fuel pump and now I have a spare. Oh, well, maybe I'll build a coy pond with an expensive circulating pump. LOL

A 10 buck can of conditioner would be a LOT cheaper and easier fix than cutting out and replacing the old convert. AND get my wife off my back a LOT quicker. LOL
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Thursday, May 22nd, 2014 AT 9:23 PM
Tiny
JDBKNIFE
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By the way Doc, my wife reminded me of something. A couple months ago, she hit an 11 point white tail buck hard enough to do 3500 bucks in damage. MAN that was some expensive burger. LOL

But the point is, do you think that the impact might have damaged the catalytic converter. I know those things are suppose to be pretty bullet proof, but it's just a thought?
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Friday, May 23rd, 2014 AT 11:17 AM
Tiny
CARADIODOC
  • EXPERT
I don't believe stuck clutch plates are the issue. To get a fault code related to the clutch pack staying applied means it was set by the pressure sensor for that clutch pack or hydraulic circuit. Clutch plates physically burned and welded together is a mechanical thing that is not monitored, so that wouldn't set a code.

A stuck clutch pack would cause other symptoms too. If you look at the truth table in the service manual, it will list each clutch pack and in which gear(s) it is applied. I don't know which ones are applied when, but as an example, lets say the under-drive clutch is applied in second and third gears but not in fourth gear. If that clutch pack was sticking, the transmission may go into second gear when the hydraulics are telling it to go into fourth gear. If yours is going into all gears properly, I would suspect a different type of problem.

There could be a problem with a sticking pressure switch telling the computer there's hydraulic pressure applying the clutch pack when there should be no pressure. Mechanically the transmission is fine, but electrically it's giving incorrect information to the computer. There could also be a problem with the hydraulic circuits. If the pressure is bleeding off too slowly, a clutch pack may appear to be applied for a fraction of a second too long and will overlap the application of another clutch pack. Excessive wear could take place during that fraction of a second when two clutch packs are fighting each other by trying to rotate at different speeds.

I'm not a transmission specialist. I can only go by what I learned at some Chrysler schools in the '90s, but this might give you some ideas of what to look for. I've heard some people say they've had good luck with "Sea Foam" products, but I've never used it, or anything else in a transmission for that matter.
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Saturday, May 24th, 2014 AT 12:15 AM
Tiny
JDBKNIFE
  • MEMBER
Yep, IF I'm understanding your point Doc, that's a big help. It kind of confirms what I was thinking. If it IS a problem being caused by the transmission, my first thought was the valve body, as us old school 724 Mopar guys call 'um. LOL

I even said that to the mechanic when he came back and told me the OD clutch was engaged all the time. I even went so far as to look up some info on rebuilding the solenoid packs in the thing once I discovered it had electric solenoids in the modulator. A faulty signal from that just makes more sense than a stuck clutch pack since the thing DOES shift normally as long as it's not under heavy acceleration.

The info I found on rebuilding the thing also said that one thing that could happen is metal particles could build up around the valves because of the magnetism of the solenoid coils. AND that could cause them to stick. So that sounds like a possibility.

Thanks. That gives me something quick, easy and inexpensive to try. I think I'll try a flush and then changing the fluid and a conditioner in the transmission before I do anything else. It can't hurt the situation and it might just cure it.

I may, if I can find the correct info and actually manage to reach the dang thing, even drag our my meter and test the connectors to make sure there isn't a continuity fault with that solenoid. Not sure exactly how to do that, but I'll try.

I AM still confused on how it can cause what FEELS like the part throttle loss of power and surging symptom it has, but then computer control modules are alchemy to me anyway. So I guess I'll just have to accept my intellectual limits for the time being. LOL
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Saturday, May 24th, 2014 AT 8:40 AM
Tiny
JDBKNIFE
  • MEMBER
Ok, Doc. I found the Sea Foam brand transmission conditioner and used it. To be honest, I THINK I could feel a difference in the smoothness of the transmission's operation, but only marginally so. AND the performance issues are UN changed. GRRRRR!

After nearly a month of this, I am getting VERY aggravated. I'm about to go postal on the wife's little car. I'll post a youtube vid so you to see the holes if I do. LOL

Seriously, the way I see it, I'm down to two options. The solenoid OR the catalytic converter. And the price for replacing the modulator and the converter is just about the same. So that's a push. To be honest and looking at the work involved, the catalytic converter will probably be the easiest thing to get at for me.

SO, I just have to make a choice as to which one would likely solve this. Is the overdrive REALLY engaged all the time or is that some fault that's been going on for a long time that's unrelated to the performance issue and the transmission expert's proclamation that it's a cat converter is correct?

OR, is it an overdrive fault coming from the solenoid causing apoplexy in the computer control module's software, which is causing the performance issues due to conflicting inputs? THAT is something I don't even know if it can cause these symptoms. And as of yet, have not been able to find out.

Not to mention that if it really IS the OD clutch pack fried and I replace the solenoid I've wasted that time and money and I will STILL be left replacing the transmission. GRRRR!

I'm so confused. LOL

At this point, unless you have another opinion, I'm leaning toward replacing the cat converter since it can't hurt and it will likely improve the performance and fuel economy of a car with this many miles on it. And it will pretty much put to bed the disagreement between the mechanic that scanned it and the transmission expert he sent me to.

What say you, Doc?
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Sunday, May 25th, 2014 AT 10:47 AM

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