Mechanics

1500 --- ENGINE CUTS OFF RANDOMLY

1997 Dodge Ram

Computer problem
1997 Dodge Ram, 5.2L V8, 4x4, Automatic 149000 miles

The engine cuts out randomly (all 8 cylinders) at random RPM's. The truck remains in gear, sometimes stalls entirely, other times it stalls momentarily and begins firing again. It appears to happen more when the engine is warmer. The "gen" light and "engine" light pop on as the engine shuts off, and they quickly go out. The difficulty is that the engine throws no engine codes at all.

~ Midas says it isn't a blocked exhaust.
~ The Dodge dealership said it was a blocked exhaust (and sent me to Midas).
- This is after they said the computer needed a reflash (so it was reflashed)
- The crankshaft sensor needed to be changed (so a new one was installed)
- The distributor was bad (tested: passed)
- The throttle body was clogged or malfunctioning (cleaned; tested: passed)
- or that the fuel filter was clogged/fuel pump malfunctioning... (tested: passed)

Thus far everything they tested (listed above) passed the tests the dealership, the first shop, and Midas put it through.

Making things MORE difficult is that the computer logs NO engine codes. None of the above resulted in a change in performance.


http://www.2carpros.com/forum/automotive_pictures/541404_dodge_1.jpg



In some form of irony, ran into my next door neighbor with a 1998 diesel Ram who had similar problems. He ended up needing a new computer and had it flashed at the dealership.

Who can tell me what's wrong!? The truck is a bit of a project truck and slowly coming along... but it'd be silly to dump more money on repairs that the truck is worth.
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Ragnarok1983
June 20, 2010.




Hi ragnarok1983. Welcome to the forum. Intermittent problems like this are almost impossible to diagnose when they don't act up long enough to do any troubleshooting. Diagnostic fault codes help but they don't solve every problem. One tool a mechanic can use is a scanner with a record / playback feature. I use the Chrysler DRB2 and DRB3, but I also have an OTC Monitor 4000 for older cars. There are also versions of scanners that can be left with the customer as long as necessary. When the problem occurs, you press the record button. Since the sensor data passes through the scanner's memory, the recording actually begins a few seconds before the button is pressed. Later, the mechanic can scroll through the data slowly, looking for a glitch with a switch or sensor.

You know the problem is not related to a plugged exhaust because it would act up all the time. The most likely suspects are the crankshaft position sensor and the camshaft position sensor in the distributor. Don't overlook something as stupid as the ignition switch. There have been a lot of problems with them developing overheated contacts and overheated terminals in the connector, but it usually affects a different circuit that feeds the heater fan, power windows, and radio.

The only thing that is not monitored by the Engine Computer is the fuel system. Specific conditions must be met to set fault codes so you still could have a bad sensor, but it just might not be acting up long enough for the code to set. It is very rare to have a fuel system problem cause intermittent stalling. Once the fuel pump starts running, it rarely stops running on its own. More commonly they fail to start up so they cause a no-start condition. The exception would be if the pump stops running due to a wiring problem. If someone jambed an add-on terminal next to a fuse terminal, such as when adding a cell phone charger, it can spread the fuse socket terminal. Later, when that add-on terminal is removed, it leaves the fuse loose in its socket. You might consider swapping the fuel pump and Automatic Shutdown (ASD) relays with other similar ones. If the problem still occurs, at least you know it wasn't caused by the relays.

If you can find someone with a scanner, you can read when the ASD relay is commanded on. It should turn on for one second when turning on the ignition switch, then again during engine rotation, (cranking or running). When the engine stalls, observe if the ASD relay is being told to turn off by the Engine Computer. If it is, you will lose spark and injector pulses, and possibly the fuel pump while it is off.

There are a lot of used scanners available when people upgrade to something newer. You can find a lot of them on eBay but look for one with the record feature. There are also a lot of code readers that do not show live sensor data while you're driving. Don't waste your money on those. You can read codes on your truck without any special tools. Chrysler products are WAY easier to do than any other brand. Also consider looking for the guys who drive the tool trucks. Mac and Matco are my favorites. There's also Cornwell, and there's Snapon if you have too much money. They all sell their own version of scanners and they will trade in older ones. Ask to raid their " trade-in" drawer. Sometimes they will know of a mechanic who is looking to sell their scanner directly to someone so they can buy a newer one. A real popular one was Snapon's MT2500, commonly referred to as the " red brick". Just be sure to check the labels on the two side-by-side cartridges to see if they are for your model and year vehicle. If you're really serious, look for the Chrysler DRB3 on eBay. There is a $6200.00 kit that you can find for around $4000.00, but it includes a lot more stuff than you need for just your truck. If you're on frinedly terms with the guys in the dealer's parts department, they can order you just the scanner and the cables for your truck for, I think, around $3500.00. The problem is the newer models only work on vehicles back to '98 unless you buy a plug-in card. But that card allows you to read emissions-related data, (sensor data) on any brand and model of car sold in the U.S. After 1996.

My final thought for the day has to do with your front wheels. If you're happy with the look and handling, at least understand that the deep offset puts a very heavy strain on the wheel bearings. The bearings have two rows of balls, and the original wheels placed the weight of the truck right between them. Using offset wheels moves the weight to the outer row of balls and makes the hub want to twist the bearing in its housing. As a former suspension and alignment specialist, I used to cringe everytime I saw those wheels. On the other hand, you should also understand that you may never have a bearing problem, or, ... More likely you'll have one become noisy regardless of whatever type of wheels you have. I only mention this to people because it COULD cause a problem and if it does, I want you to blame the wheels, not Dodge.

Caradiodoc

Caradiodoc
Jun 21, 2010.
As far as the wheels go, yeah, that large offset is a not what I'd prefer, but it's how I bought the truck. The picture submitted is old, and since then I've purchased new wheels that tucked them in more.

Unfortunately, they only tucked them in another inch to 1.5 inches or so, and not the 2.5 to 3 inches it needed to be back on center.

Back to the engine problem...

I'll try the camshaft position sensor in the distributor. I might as well as I grabbed a new distributor when we figured that was the problem. I'l go and do them both I suppose. Can't hurt anything but the wallet.

Drove around with my buddy's scanner for two days and it didn't get a thing. Haven't checked the ASD yet.

A funny sidenote: The dealership claimed it may be a blocked catalytic converter. I jumped under my truck to check out the exhaust system in case I needed to replace part of it.

The funny thing... damn truck doesn't have a catalytic converter. Damned prior owner replaced it with a test pipe. Kinda tough to block something that doesn't exist.

If I ever do get this thing fixed, I'll put on an appropriate vanity plate. I think "LEMON" would fit well.

Oh... while I was down there, I found this 2-3 foot long stretch of cord (4ea 10 or 12 guage wire). Thing was unplugged and I don't know where the heck it goes but it was nearly dragging on the ground. It was hanging on the passenger side of the transmission.

(you can tell I'm not a mechanic; anything I "know" probably comes from a Haynes manual)


http://www.2carpros.com/forum/automotive_pictures/541404_wireHuh_1.jpg


Tiny
Ragnarok1983
Jun 21, 2010.
An inch less offset makes a big difference. The alignment mechanic in me is happy to hear about the new wheels.

What's on the other end of that plug, wires or vacuum hoses? Beginning with '96 models, every vehicle sold in the U.S. Had the On-Board Diagnostics version 2, (OBD2) emissions system. Besides having a lot more available trouble codes, it included a second oxygen sensor in the exhaust right after the catalytic converter to monitor its efficiency. V-type engines usually have two catalytic converters, and each one has an O2 sensor right before it and right after it for a total of four sensors. Removing the converter(s) should have caused the Check Engine light to turn on, but I also think I heard there is something made that can be plugged into the harness to trick the computer into thinking the converters are there and working. That would be illegal but that's beside the point.

The way the system is supposed to work is the first oxygen sensor reads how much unburned oxygen is in the exhaust and develops a tiny voltage as a result. The computer sees that lean condition and commands the fuel injectors on that bank to stay open a little longer, (measured in milliseconds), for each squirt to enrichen the mixture. Next, it doesn't see a lean condition so it commands the injectors to remain open for a shorter period of time. The result is the sensor will switch from rich to lean to rich back and forth up to a few times per second. When the exhaust goes lean, the extra oxygen is stored in the catalyst bed. When the exhaust goes rich, the extra fuel going through the catalyst has that stored oxygen to mix with so it can burn. The result is no unburned hydrocarbons leave the tail pipe. That was how all fuel injection systems worked since the early 1980s.

With OBD2 in '96, the second O2 sensor watches the mixture coming out of the converter. The mixture going in switches between rich and lean many times per second. If the converter is doing its job, the mixture leaving it will switch between rich and lean once in a long time, perhaps many seconds. As the converter loses its ability to do its job, the switch rate of the gases leaving it speeds up until eventually it matches the switch rate of the gases coming in. That means there is no change taking place as the gases pass through the converter.

When the magic number is reached where the " downstream" O2 sensor is switching too fast, the Engine Computer sets a fault code related to converter efficiency for that side and turns on the Check Engine light. If the converter is removed and the O2 sensors are still in place, that code should be set too since both sensors will be reading the same and switching at the same rate. A different code will be set if any O2 sensor is simply unplugged.

That connector in the photo is the shape of an O2 sensor connector but it looks more like hard rubber. That could be a vacuum hose connector for the four-wheel-drive switch on top of the transfer case. Those switches gave some trouble if moisture got in there. The switches would stick and cause the 4wd light to stay off or on, I can't remember. It switches vacuum to the vacuum motor, (actuator), on the right side of the front axle to lock the two axle shafts together. When they are unlocked, it allows them to turn at different speeds when cornering without forcing the front driveshaft to turn. That reduces the force needed a little to improve fuel mileage. When rust develops in that switch, it either sticks in 4wd or 2wd. Can't remember which, but if you unscrew the switch from the top of the transfer case, you will see a round metal ball on the end and it will be full of rust.

Caradiodoc

Caradiodoc
Jun 21, 2010.
"Mysterious wire/cord" = Vacuum system:
Yeah, definitely vacuum. I found where it is supposed to plug in (drivers side on the transfer case) Now I just have to figure out which way the dang thing is supposed to plug back in. It makes sense after the last time I had a bit of mud on the truck and could see my front wheels weren't turning (while the backs ones certainly were). Anywho, I went to go reattach the female end to the male end hoping it was one of those "dumbproof" connections, but the male housing isn't "keyed" like female side. It's just four male ends sticking up. I stuck it in the way in naturally bent for now (as pictured with the notched end pointing toward the front passenger side).


http://www.2carpros.com/forum/automotive_pictures/541404_vacuum_1.jpg



Catalytic Converter:
Yeah, I have to go locate a cat system and then find a way (financially) to rectify the situation. The previous owner definitely bypassed something in the sensor system, as the cat has never popped up on previous engine codes. Having looked at the exhaust, this issue good thing in a way. Turns out there were some exhaust leaks and gaping holes after the muffler and pointing up (right under the rear seats in the cab).

Maybe I'll just get the "POS TRUK" as a vanity plate, haha. I never liked Dodges, but I can't blame this on Dodge... at least not entirely. If the previous owner wasn't a guy I vaguely respect, I'd smack him upside the head, hahaha.

Suddenly that military surplus chevy "C/K" looks pretty good in comparison. Haha.


http://www.2carpros.com/forum/automotive_pictures/541404_CK_1.jpg

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Tiny
Ragnarok1983
Jun 21, 2010.
I'm not a fan of GM, mostly for their business practices that bleed money from their unsuspecting customers. It would take way too long to explain all of the things Chrysler did better back in the 1960s through the 1990s. The '02 and newer GMs are really bad. Ford isn't much better.

I forgot to mention, with the crankshaft position sensor, ... If you remove it, a paper spacer must be stuck to the end of it to set the air gap. If it is too little, the sensor could be broken from hitting the flex plate. If it is too big, there engine won't run or will stall intermittently. Some replacement sensors have a plastic rib molded onto the end to set the gap. Either that rib or the paper spacer is supposed to shear off when the engine is started. If your sensor has the plastic rib, cut the remaining part off and use the paper spacer.

Caradiodoc

Caradiodoc
Jun 21, 2010.
Well, replaced a bad ground, did the camshaft position sensor, and plugged in the vaccum lines, but kept the old distributor in as it appeared to be working fine.

Truck runs without issue, though I feel that the timing is off just a bit (it's ALWAYS felt like that though). I'll get that fixed in a little bit.

Threw on a brand-spanking-new $30 muffler and replaced the leaking exhaust pipes too. Haha. Why the hell not.

Anyway, thank you a great deal for the advice. The one dollar donation and elbow grease would have saved me the other $699 that the shop charged me for NOT fixing the problem.

Glad this episode is over. Thanks again!

Tiny
Ragnarok1983
Jun 22, 2010.
Happy to hear it's running Holler back if you have more problems.

Caradiodoc

Caradiodoc
Jun 23, 2010.

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