I posted a thread a while ago and got some suggestions, but still need some help. I've been having problems with my T/A when it goes into closed loop. It runs absolutely fine when cold, but has no power and runs very poorly when it gets warm. Here are the things I've replaced or checked to be OK:

1) New O2 sensor
2) New coolant temp sensor
3) New wires, distributor and cap
4) EGR valve is good and holds vacum
5) TPS 5.3v at idle
6) Tried new MAF and power relay (no change so I returned them)
7) Hooked up TunerPro and am not getting any codes (everything appears to be working)

Someone suggested it could be the PCV system, but everything is completely stock and there doesn't seem to be holes or cracked hoses. Since the car does run well when I first start it up I wouldn't think it could be anything serious, but I am out of ideas and suggestions. What else could affect the car when in closed loop? What specifically can I start looking for and checking next? Any help appreciated!

 

TPS 5.3 at idle ??
Methinks it should be closer to 0.53. ( exact voltage isn't critical )
If you hook up Tuner Pro and watch the TPS ( no need to actually atart the engine ) does it follow your foot relatively smoothly ?

What kind of BLM's are you getting ?

 

have you did a vaccum check and compression check

 

Yes, the TPS was at .53 and it seems to follow my foot smoothly. The BLM if I recall correctly was at 128? Does this sound right?

I have not done a vacum or compression, but if I dropped a cylinder wouldn't the car act up even when cold?

Thanks!!

 

That's unfortunate ! A bad TPS would have been an easy fix.

Unfortunately, it sounds perfect !
The only clue it might provide would be if it remains solidly at 128 when in closed loop, with no variance at all. That's really not possible on a working O2 sensor, and a working ECM.
There pretty much has to be some variance.

One would think, yes.
I'd expect that if it did drop a cylinder, the exhaust O2 would go high, giving a false lean condition, BLM would go high to compensate, flooding ( or at least going very rich ) the engine.
Likely you'd smell that, and have an overheated CAT, plus see it in an abnormal BLM.

About the only sensor that's not used in open loop, is the O2.
If TunerPro is showing "normal" O2 sensor action, I'm stymied !
Since it runs OK open loop, I'd not be too concerned about compression, and the MAP sensor *is* a vacuum guage, sort of.
I'd want to question the CAL in the PROM, except that you've given no indication that it's not stock. Very weird. I'll be interested to know what it finally turns out to be.

 

Maybe I'm overlooking something simple. Can you tell me about what ranges the TPS, O2 sensors and BLM should be working under both open and closed loops? Thanks for the help, I will post the solution if I ever come to one.

 

TPS is entirely dependant on the position of the loud pedal. Less than 0.7 at idle, above 4.5 at WOT, and most anything in between is proportionally linear. This works ALL the time, and doesn't matter whether it's open or closed loop.
BLM should be a solid 128 in open loop. ( not working ) When in closed loop, should vary some depending on history and fuel map between about 120 and 136 or so. Might be more, might be less. BLM is a fuel correction. Goes where the O2 sensor tells it to go. Exreme limits are generally about 108 and 156.
The O2 sensor should start out staying about 0.456 volts, until it starts to warm up, and start working. Then, it should oscillate from about 0.1 to about 0.9 maybe twice per second.
Open loop, say foot in it hard, it should hang around 0.9 ( rich ) as the ECM commands excess fuel for acceleration. There should be some variance for driving conditions otherwise, but still showing a tendency to oscillate a couple times per second.
On a long down hill decell, it may go to 0.1 and stay there a while, as fuel is cut off during a long decell, then start oscillating again as the vehicle slows, and the engine resumes running.