I have had this problem for over a year now on my 97 M6 Z28 where the car where barely run when it switches into closed loop mode. In the mean time to avoid the problem I have been running the car with a OBD1 conversion PCM tuned to stay in open loop where the car runs great. With my stock ODB2 PCM the in closed loop the car will miss, stumble, black smoke like crazy and it basically un-driveable. Some things I have done to fix include:
-3 new sets of GM 02 sensors
-2 new sets of rear 02 simms
-made sure there are no exhaust leaks from long tubes or y-pipe
-pulled entire wire bundles out to ensure no burning of wires
-2 sets of new and used 02 extension wires
-swapped MAF's with roommates identical car
-swapped his MAP sensor
-swapped IAT sensors
-swapped optis
-changed plugs 2 times
-changed wires to over the tops
-tried running the OBD1 in closed loop does same thing
-and just today I swapped out for different injectors

This is REALLY starting to **** me off now I have tried everything I know of, and the fact that the car runs perfect in open loop eleminates a bunch of possibilites itself. I had the car scanned when it was barely running came up with a couple codes. Those were:
P0133 Bnk 1 Sens 1 02 slow response
P1153 Bnk 2 control shifted lean
P1133 Bnk 1 Sens 1 insufficient switching

These are obviously 02 sensor codes but I have done everything I could to basically eleminate the possibility of them being the cause. Last night we ran a program on the car to see what things were doing my Bnk 1 02 sensor was stuck at 930 and my Bnk 2 sensor was sitting at 400 neight of them were moving much at all. This isnt 100% but I swear all this happened around the time I did my long tube headers. So my question is what else comes into play when going from open loop to closed loop thats making the car barely run? Someone please help me before I drive this car off a cliff.
Thanks

 

Wow, that is a good one for sure.

I'll assume you've checked other obvious things like running the OBDI puter in closed loop to determine if it's a PCM problem.

Next I would check the O2 pin connectors and make sure there is continuity between those connectors and PCM connectors if you can trace it that far up.

The fact that it happens only when closed loop leads me to believe it's either a sensor, or the wiring to a sensor. If this all started after the install, you may have pulled a loom of wires too hard or something like that.

Sounds like you're on the right track, just dig a little deeper.

Good luck,
Mike

 

sounds to me like you fried your 02 wires on a header. rewire the front 02 sensors from sensor directly to pcm. in other words.....bypass the stock wiring.

 

I just logged a few runs in my car and came up with the left side 02 sensor sitting at over 900 during WOT and right side right around 100. That aint right!

rewiring the 02 sensors will not be a problem but when you say re-wire all the way to the PCM do you mean just splice into the stock wire where it plugs into the connector at the PCM? I pulled the p[assenger side wire bundle out and a couple of the wires were slightly burnt with the shielding coming off but I taped them up no wires were actually seperated. Let me know what you guys think now.
Thanks

 

bypass the whole suspect area. eliminate the 02 wires that were burned.

WOT it is normal for 800+ mv

you need to watch the 02s at idle and cruise.

you should get 02s crossin over .500 constantly at closed loop.

 

ok I read the 02's at idle, cruise, and WOT. Surprisingly the readings didnt change much between the three types of driving. The left 02 sensor constantly sat around 900-950 at cruise/idle/WOT, and the right side was around 100 in all phases.

The side that has some slightly burnt wires is the passenger side.

 

Does it still do it at WOT? If not, then it might be o2 sensors. If it is still doing it at WOT, then the o2s are notthe problem.

Computer doesnt use o2s at WOT.

 

It may not use them at WOT, but it does still monitor them and you can see that on a scanner.

Maybe you have some bent pins on your PCM. Seems you definitely have a problem with continuity to or operation of your O2s.

 

with your 02s not moving, it sounds like the 900mv side is shorted to 12+ and the 100mv bank is shorted to ground. bypass the burned wires and see what happens.

 

OK NOW IM PISSED!!! I just spent all friggin day re-wiring all my 02 wires. I just finished and drove the car took all of about 4 minutes for the SES light to come on and start flashing and car barely running. I think maybe tomorrow I will try one more pair of new 02's since I now repaired all the wiring. Any ideas now? this is getting rediculous.

 

check all your fuses under the hood and side of dash. on some cars, the 02 sensor heating elements power off a fuse. it might have blown, shorting on the header.

 

the 2 white wires on the 02 sensor side harness are 12v. and ground with key on.

also where are your 02s located?

 

Both 02's are located about 6" aft of the collectors on my longtubes, or about 6" before the LT's bolt up to the y-pipe. Basically next to the tranny. The drivers side 02 is mounted toward the tranny side while the passenger side is mounted towards the outside of the car. I will check all my fuses tomorrow. But now I can 100% eliminate the possibility of a burned wire. If there are no blown fuses, or trying a new pair of 02's doesnt work I am clueless. Is there anything else it could be like a knock sensor or temp sensor that has anything to do with closed loop, or has anyone heard of long tubes in general not working correctly causing messed up readings for the 02's?
I dunno cant think of anything else.
Thanks again,
JT

 

All fuses on the vehicle are good.

 

unplug both sensors and run the car, see what the sensors read

should stay at or near 450mv