Bank A closed loop, bank B open loop due to unmet conditions

Tiny
AUSTIN78989
  • MEMBER
  • 1997 FORD PROBE
  • 2.5L
  • V6
  • 2WD
  • MANUAL
  • 119,400 MILES
I have a live data scanner that I use to get the information in this post.
I know it is a lot of reading, but I put everything out onto the table here in hopes that somebody could help me out. I have tried almost everything.

Problem:
The car starts and runs fine, however it runs extremely rich. My live data scanner shows that bank A is running closed loop, while bank B is always running open loop due to unmet conditions.

Bank B stays in open loop due to unmet conditions. The only time it switches to anything else is when I press the gas and the live scanner shows both Bank A and B in open loop due to driving conditions, however when the rpm's settle bank A goes closed loop, and bank B is back to open loop due to unmet conditions.


Work done prior to problem occurring:
All vacuum lines replaced.
Intake, valve cover, and throttle body gaskets replaced.
all 4 o2 sensors replaced.
Spark plug wires replaced.
Spark Plugs replaced.
Distributor replaced.
timing set perfectly to 10 degrees btdc
idle at 650 +- 50 rpm's (set accurately via live data).
Throttle position sensor perfectly set to 0% at idle.


After all of this work was done the car started and the live data scanner showed that both banks where in closed loop, the car sounded great and idled perfectly around 650 rpm's for a while.

I was playing some music, and letting the car idle for a while (twenty to thirty minutes) testing things out, and suddenly I felt the idle get really rough, and I could hear some misfiring going on little pops here and there, and when I would press the gas pedal there would be missing and it wouldn't be very smooth.
I immediately pulled out my live data scanner and I was seeing.

BankA: Closed loop.
BankB: Open loop due to unmet conditions.

Coolant temperature: (around 200 degrees F at the time).

Throttle position: 0% ( no dead zones all the way to 100%).

O2 Bank 1 sensor 1: swinging back and fourth between 0 and 1v
O2 Bank 2 sensor 1: swinging back and fourth between 0 and 1v

For whatever reason o2 bank 1 sensor 2 and 3 ( pre and post cat o2 on my car) are intermittent, they seem to only show up when the car is in closed loop, or diagnostic mode is triggered sometimes. The pre and post cat O2 sensors are the four wire sensors with the fourth wire being a ground, I tested the ground points, and everything looks good. Also, considering in closed loop, the sensors go between 0 and 1 volt fine I do not think they are an issue either. I have replaced them for good measure though.

O2 operation on this car (from what I have witnessed prior to this issue).
Bank A and B closed loop: all 4 sensors work
Bank A or B Open loop: only upstream sensors work (b1s1 b2s1).
Diagnostic mode bridged: all four sensors kick on and work.

Currently both upstream o2 sensors are working fine, and with diagnostic mode jumped all sensors show up just fine.

Diagnostic mode not jumped = working front o2 sensors with intermittent pre and post cat o2 sensors.

Vane airflow stats:
The intake air temperature was around 108 which made sense being that it was taking in air straight after the radiator fans, and the car was not exactly cool.

The airflow rate seems to match up with what it should be doing, as the rpm's go up the intake air speed numbers rise, and fall with engine speed.

The idle is less steady it does not hold a perfect 650 very well with half of the engine running open loop. It bounces a lot between 600 and 700, but stays within those boundaries.

Worst of all is that the car is running super rich now.

I noticed a map sensor problem as well, if I have the map sensor hooked up the fuel trims spike, and keep climbing past 35%. There is so much fuel being added that raw fuel vapor is exiting the pipe (not water), the ECU would then attempt to make some sort of correction and the fuel trims would go back to 0 then the idle would drop quickly and sometimes stall the engine. So I put a new-used map sensor on ($140.00 plus from Ford or Mazda new). The new-used one seems to work intermittently, the short term fuel trims spike and drop, the ECU does not seem to know how to correct and the car starts misfiring, idle increasing, decreasing, and things get really rough, and sometimes the car simply stalls out.
When I disconnect the map sensor the car runs with a nice more-less smooth idle, (as smooth as it gets running half open loop) and there is no random bogging of the engine as the ECU over compensates.
Basically with the map sensor totally disconnected the car runs with long term fuel trims around 10% +- a few percents. On both banks.

I have tested the live data of the car prior to this problem with the map sensor removed, as the random bogging at idle happened in the past, and the car ran in perfect closed loop with the map sensor totally removed from the system. So I do not personally believe that the map sensor is related to this whole mess, and I am unsure if its my map sensors that are bad, or something else that is bad.

I tried to get the long term fuel trims to come down to 0% to try to reduce the rich smell of the exhaust.

I found that unhooking the vacuum line to the fuel pressure regulator causes the long term fuel trims to hover around 0-2% on each bank, +- a few percents on the short term, which I would imagine is a good number.

The exhaust is still quite rich, however with this setup it is not pushing as much raw fuel out of the exhaust pipe.

I have tried swapping bank A and B o2 sensors.
Same error on bank B.

I have replaced all of the injectors with known working injectors. (Tried all different injectors, and tried the bank A injectors from two different sets and still have Bank B running open loop due to unmet conditions.

I have compression tested the engine, and made sure to test for head gasket leaks, absolutely no sign of a head gasket leak ( if there was a blown head gasket it would have randomly occurred sitting at idle for twenty to thirty minutes ).

I cannot remember the numbers, but I remember checking the workshop manual and the numbers where indicative of a very healthy engine.


At this point I am at a loss as to what is causing my Bank B open loop issue.

Bank A always goes into closed loop no problem.

Bank B always goes open loop due to unmet conditions as soon as bank A is in closed loop now.

I have a spare ECU, and it gives the exact same errors so I do not believe this is an ECU related problem.

Also, I do not have a vacuum gauge, but the vacuum to the map sensor location feels very strong.


A few things to keep in mind:

I happened to test this in the past, and my car runs closed loop just fine with the map sensor disconnected prior to this current issue.
The error occurs with map sensor plugged in or unplugged.

My car has a small pinhole fuel tank leak at the top of the tank ( it drips when I top off the tank ) - this never caused an open loop issue in the past, and has not thrown any codes.

When this happened the car was idling twenty to thirty minutes with music playing, and the AC turned on. I know it is bad for the compressor to do this, but I was messing around with equalizer effects and this was one of those few exceptions.

The car being the age it is, has very little rust on the underside, it is in pretty good shape. It has been kept in southern states most of its life.

When the fuel trims drop down (map sensor disconnected along with fuel pressure regulator vacuum line disconnected), there is little to no visible vapor coming from the exhaust. The trims stay within 10% all the way to full throttle with this setup, and still smells rich.

Diagnostic mode is something on this car that disables the IAC operation, and prevents ECU from changing timing so one is able to adjust idle, and timing accurately, and help diagnose various issues linked to diagnostic mode.

I do not know what else to say, I just want closed loop to come back so my car does not stink, and I have some decent gas mileage.

I am sitting here with a trunk full of extra injectors, fuel rails, fuel pump, map sensor, vacuum lines, and various distributor parts, I do not know what caused the issue to start, and I do not know how to fix something that is not throwing any codes, or giving me any real indications of where to look first.

These are currently the only screenshots I have of the current O2 sensors working. In these screenshots I had the post catalytic converter o2 sensor disconnected, however I had proper readings across the board from all sensors. The fuel trims are about what I get with the fuel pressure regulator correctly connected to vacuum, the trims drop down around five or less when the vacuum line is removed from the fuel pressure regulator.

All of the spark plugs are identical in appearance. (See spark plug images)

I cannot seem to remove the pictures that all posted in duplicates. This is a tad frustrating and misleading. There are only three pictures I was expecting to post.
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Friday, October 20th, 2017 AT 9:04 PM

7 Replies

Tiny
STEVE W.
  • EXPERT
Grab a meter and test the wiring going to the O2 sensors. A broken wire or bad connection to either one can cause it to go open loop as it does not see the sensor actually sending info to the ECU. I would bet you have a couple O2 codes as well.
Do not miss areas around the exhaust or where the harness crosses a sharp area, the wire could even be broken right at a connector and only making intermittent contact, that would explain why the sensors do not show in live data all the time (they should show in both open and closed loop as they are continuous monitored items).
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Friday, October 20th, 2017 AT 9:28 PM
Tiny
AUSTIN78989
  • MEMBER
Sorry, I was making an attempt to post pictures, and added a bit on how the o2 operation works on this car. It is different to say the least.

I only wanted these few pictures to post, but extras made it in there and got duplicated a bit. Sorry about that.

Anyway,
in those graphs the post catalytic converter O2 sensor was disconnected. However, when it is connected all sensors work normal. However the issue persists.

I have tested all of the O2 sensor wiring as well, and have good connections. Unless you are thinking that this might be caused by maybe a corroded wire maybe adding resistance of some form to the signal, I do not see that being the problem.

The car was running perfectly fine with all o2 sensors showing prior to this issue, it was sitting in the drive way idling when it suddenly had bank B go open loop.

The thing is even with all of the o2 sensors showing up doing exactly what they should be doing, I am still in open loop on bank B.
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Friday, October 20th, 2017 AT 9:50 PM
Tiny
STEVE W.
  • EXPERT
Plug in the sensors. Then give me a screen shot of long and short fuel trims at idle and at say 2000 rpm. Also a shot of the sensor voltages at both.

FYI, if the fuel trims are being adjusted on both banks the engine is in closed loop. It cannot be in closed loop on one side and not on the other. The ECM controls both sides in closed loop, but you could easily have a bad injector on one bank dumping fuel either through a bad injector or a failed o-ring at the bottom and it is dumping fuel directly from the fuel rail.

That tool does not allow you injector control does it?
Got a fuel pressure gauge? Toss it on there and start the engine, watch the pressure, now shut it off. The pressure should stay the same, if it drops off you have a leak, either a failed 0-ring or injector. It would only take one to dump enough fuel to cause a problem.
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Saturday, October 21st, 2017 AT 1:30 AM
Tiny
AUSTIN78989
  • MEMBER
I did some tinkering today, and found that the rear valve cover gasket had a large leak when I tried blowing air into the valve cover breather hole there was absolutely no pressure. I was able to easily pinpoint exactly where the gasket was not sealing. It apparently did not seal all the way when I replaced it.

I replaced the gasket again, this time I am sure there is absolutely no leak. I will not be able to test the car until tomorrow afternoon due to some of the gasket maker on various trouble spots needing to cure.
I am pretty positive this will correct my open loop issue.

Steve w. I have about twelve injectors in total (six spares), I made sure all of them are firing, rebuilt, and I have tested injectors from both banks on both sides. All of the injectors click on and off properly as well, I checked with the screwdriver stethoscope method.

This large vacuum leak would explain why my computer is pumping extra gas into the engine, and why my map sensor causes the car to idle crazy and die, or dump fuel in (low vacuum due to massive leak).

I will let you know tomorrow what my end result is.
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Saturday, October 21st, 2017 AT 6:02 PM
Tiny
STEVE W.
  • EXPERT
Yep a vacuum leak would do it, especially a large one. Figured that was something you had already checked as you seem to have a clue on auto repair. Hope it clears things up. You will want to change your oil to get the extra fuel out of the system.
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Saturday, October 21st, 2017 AT 9:57 PM
Tiny
AUSTIN78989
  • MEMBER
Yeah, I thought when I replaced the rear valve cover gasket that I had it on pretty good the first time, apparently not.

I tested the car today, and I have good news and bad news.

Good news:
With everything connected correctly, fuel pressure regulator, vacuum lines etc. I no longer have a rich condition.

Both banks are running around 3% long term fuel trims with short term fuel trims bouncing around -0.8 and 1 or 2.

There is now no visible gasoline vapors coming from the exhaust, and the smell has cleaned up quite a bit.

The bad news:

Both of my map sensors (factory, and spare) still have issues when connected. One will cause the engine to immediately dump fuel in, and spike the fuel trims up past 25-30%, while the other causes the engine to buck and stall with totally random fuel trims.
(map sensor disconnected = car runs absolutely fine and the fuel trims are steady around 0).

I do not know where else a vacuum leak might be because I capped off the PCV vacuum on the front valve cover, and the breather tube on the rear valve cover going to the throttle body, and with both capped off the fuel trims are perfect, but the MAP sensors still cause problems.

My factory map sensor may be bad, and my spare map sensor was pulled from a parted out car, so maybe I have two bad map sensors?

There are no other vacuum leak sources I can think of, and the vacuum pulls very hard on all of the hoses, I don't have a meter but it would probably easily leave a hickie on my skin if I left a hose long enough.
I have already replaced all of the vacuum hoses, so I checked over my work while I had the intake manifold off, everything looked great.
I also made sure to thoroughly clean up all mating surfaces of the intake manifold gaskets, to ensure a nice absolutely airtight seal.

Bank A shows as closed loop.
Bank B shows as Open loop due to unmet conditions (same error as before).

The car seems to run great, still has a smell to it (but much less than before), and throttle response is pretty good. This is as close to factory as I have had it yet.

So now the question is, since the large vacuum leak was fixed, what else might be causing this issue? I am on the verge of questioning whether it is worth even looking into at this point since everything seems great now. (Except the slight smell of lawn mower)

I will need to see what my fuel economy looks like, but I would assume with everything connected properly and fuel trims within 5% of 0. I should not exactly see a large drop in fuel economy. I live in San Antonio Texas and we do not have emissions restrictions on our vehicles, so I am in no rush at this point.

P.S. Good point on the oil, I will change that pretty soon here while I do my transmission fluid.
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Sunday, October 22nd, 2017 AT 5:48 PM
Tiny
STEVE W.
  • EXPERT
Could very well be two bad sensors. Can your tool show the MAP readings? Look for atmospheric pressure with key on engine off.

Because it dumped a lot of fuel in the exhaust you will probably have a smell for a while, at least until it all burns off and the converters clear.
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Monday, October 23rd, 2017 AT 12:30 AM

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