Extremely Rich Idle

[phil4286]

I had my car running fine, then I adjusted some VE tables (idle, low RPM single, low RPM double, high RPM) by 1-3% in some values, trying to dial it in, nothing major. Flashed it back to my car, and it runs like garbage. The idle is about 9.5-10.5. Cruising is the same. This lasts for about 20 minutes, then I get a "lean" CEL. WTF, 9.5-10.5 is not lean. If anything I should be getting a "rich" CEL. Anyways, once this comes on, the car idles fine, right around 14.0-15.0. I flashed the original file I had on the vehicle back to it, and this problem still occurs. Please see attached logs. Something is really wrong, and I need some information to help me fix it. I found this issue in another post on a different forum, but there was no solution, the post just stopped.

Please any help!!!!!

[phil4286]

Here is the config file.
Sorry

[laser_racer]

Your fuel trims are wayyyyyyy off. I wonder if your o2 sensor is bad on the car. Can you put the car in to open loop and tune it?

[phil4286]

I was told tha PCM in the cavalier is the "BASTARD CHILD" of PCM's from GM. Turning off closed loop is a bad idea. This happened randomly. The previous tune worked fine, originally, then I flashed the new one, generated the problem, went back to the other tune, and the problem still occured. I think its mechanical, and I need to know where to start. I did a general vacuum leack check last night. All lines were attached, and a visual inspection showed no holes in the lines. I also sprayed ether around all vacuum connections looking for a "idle up" effect, and got nothing. I might have to disassemble all vacuum lines and check for leaks, but I would rather turn away from that, as I have 11+ vacuum lines.

[laser_racer]

I would do a boost leak test to see if you are having a problem. It makes it so much easier to find a leak then spraying carb cleaner every wheres. How come its a bad idea to stick the car in open loop? We have like -20 vac on our m62 redline.

[imphat0260]

I would do a boost leak test to see if you are having a problem. It makes it so much easier to find a leak then spraying carb cleaner every wheres. How come its a bad idea to stick the car in open loop? We have like -20 vac on our m62 redline.

We are missing an @ssload of fueling tables... Don't even have a commanded Stoich table. Basically, if you command OL, the Commanded AFR will always command a 12-13 AFR no matter what(unless in PE). Obviously this skews all AFR error readings. So through a lot of testing, myself and others that do alot of these PCMs have found it much faster/easier to tune in CL using filters on the histograms.

[laser_racer]

What all do yall have to filter out of the histogram to get it to run right?

[Leafy]

We are missing an @ssload of fueling tables... Don't even have a commanded Stoich table. Basically, if you command OL, the Commanded AFR will always command a 12-13 AFR no matter what(unless in PE). Obviously this skews all AFR error readings. So through a lot of testing, myself and others that do alot of these PCMs have found it much faster/easier to tune in CL using filters on the histograms.

Whoa there. Back in the day when I was still working the kinks out I used to force open loop, and it would still command 14.6:1 most of the time cruising but randomly would decide it was time to run at 12:1. I also could never get it to idle above 10.5:1 in open loop. That said, besides the idle issue, if its commanding 12:1 and I'm actually getting 12:1 my afr error pid will read zero, so it doesnt skew the afr error. That said, tuning with closed loop on is WAY better.

OP, sounds like an O2 issue. Force open loop and see how your afr errors look then. If they look somewhat normal then its your stock narrowband O2 that is fucked up.

[gmanz24]

I gave up on using the commanded afr error PID's and created my own custom PID's that reflected the afr i was looking for and derived my own error off that. for example during WOT i was looking for 13.3 afr, so i created a PID that derived an error solely from that 13.3, this allowed me to tune without the chance of the commanded afr changing randomly and throwing off my error numbers.

[phil4286]

So I checked for a vacuum leak. I plugged all ports on the TB, this would help isolate if the leak was after the TB (TB gasket, intake gasket, injector o-ring) or before the TB, on all the vacuum lines. The car still idled way rich 9.5-10.5. So I assumed there was a vacuum leak between the TB and the engine. I starved the TB of air, hoping that it would pull more through the vacuum leak making it louder, and easier to find. Starved the TB about 90% and was still running fine, starved it 100% and it stalled, and continued to hold vacuum, so I decided that there was no leak. The vacumm would have been lost if there was a leak. Then I removed my stock O2 sensor, and plugged in another on I had hanging around. It turned over lean, then came down to 13.80-15.2 and held. I let it idle for about 15 minutes, and it stayed there. Im going to turn it over again a couple more times in the upcoming days, before I put everything back together, to make sure this is the solution.

New Question: The sensor I had in it was a 4 wire heated, which the heating element was ran through the Bank 1 Sensor 2 wiring, because stock Bank 1 Sensor 1 is a 2 wire, non heated. I had no problems with this for 3 months. Then it just takes a crap on me. I was still working on the tune and the car was running relatively fine, no super rich or super lean conditions (11.0-16.0), which could cause a "fouled" O2. Is it possible to overheat a stock O2? I know the LC-1 has a proper temperature range, but this one is stock. My sensor is close to my turbo, all most in the same relative place the stock DSM sensor is on the DP, about 3-4" away. Could this be a problem? I will watch my EGT's more closely, but I think they are around 1200, thats in the manifold, so maybe 1000 in the pipe?

Thanks

[Dr. Nopps]

If you flashed back to a tune which previously gave you no issues, but now runs weird then yes it's most likely mechanical. When certain sensors or components on those cars fail, red flags pop up that will cause the computer to "refuse" to go into closed loop no matter what your tables dictate. I had a Snap-On scanner that would tell me whether I was in O.L. or C.L. I had my tables set up to allow C.L. almost immediately and it did, allowing me to command AFR for several months. But one day, even though I could still enter PE mode I was banned from C.L. and my AFR was uncommandable. Turns out something grew old and was dying. (An O2 sensor or injector or fuel pump or something) A week or two later, it became so obvious I didn't need scanners to see something was wrong. Also, how is it that your log on top swows 0 RPM through the whole scan?

[phil4286]

RPM didnt work on that log, HPT tends to loose some parameters when connecting to the PCM, it also tends to disconnect in the middle of logging, and come back.
Very wierd. I have been told that is normal, because the jbody PCM has a super slow processor.

[Leafy]

I havent had problems losing parameters, I do get disconnected though. real sucky for it to happen after an hour of logging.

[phil4286]

It doesnt loose parameters in the middle of logging, it just doesnt even start with them sometimes. Like RPM, MAP, MPH, AFR Error, so I have to look evertime I connect, to make sure, obviously that log I didnt double check.