Car runs and idles great, but soon as the temp hits around 95 degrees (C) [195 F], it seems like the ECM sends a signal, and then the car starts to idle kind of lumpy, almost like a bad plug firing.

I want to look at it today, so where should I start?

bad injector?
knock sensor?

I read some other posts and they were talking about the esc module.

Tell me where I should look or what you think it might be.

thanks in advance.

 

92,

The ESC on your '92 should be incorporated into the ECM itself. Older F-cars did not have the memory and I/O addressing capacity to contain the ESC logic, so there was an external module built to handle the ESC functions and simply report the status back to the ECM, where teh ECM would either enable or disable EST advance. In other words, there is no separate module. The detonation sensor should wire directly to the ECM inputs.

In either case, the symptoms you are describing may be more related to temperature dependent ECM parameters than the ESC directly. Is is possible that mixture control is taking a step at a given temperature and is affecting your idle operation. From what I've seen commonly, some temperature dependent ECM parameters include:

ECM Functions
BLM enabled between 50°C (122°F) and 140°C (284°F)
SHIFT light enabled >50°C (122°F)
Cooling fan #1 enabled at 107°C (226°F)
Cooling fan #1 off at 104.7°C (220.5°F)
Cooling fan #2 enabled at 115.2°C (239.5°F)
Cooling fan #2 off at 110°C (230°F)
Cooling fan duty cycle at 100% at 80°C (176°F)
TCC lockup enabled >50°C (122°F)
EGR Duty-cycle enabled at 56°C (133°F)
EGR Duty-cycle at MAX >80°C (176°F)
Code 13 (oxygen sensor fault) enabled above 70°C (157°F)
Code 14 (CTS high fault) enabled above 130°C (266°F)
EVAP canister purge enabled above 70.3°C (158.5°F)
Hot closed-loop timer enabled above 70.3°C (158.5°F)
A/C clutch disabled above 150°C (302°F)

Ignition Functions
Cold spark advance disabled above 56°C (133°F)
Hot spark retard begins above 116°C (240°F)
Knock Control enabled > 67°C (153°F)
DTC 43 enabled > 90°C (194°F)

Fuel Mixture Control Functions
Acceleration enrichment multiplier at 0.75 above 80° C (176°F)
Acceleration enrichment multiplier at 0.50 above 104°C (220°F)
Acceleration enrichment decay factor at 40% above 80° C (176°F)
Acceleration enrichment decay factor at 50% above 104° C (220°F)
Acceleration enrichment decay factor at 60% above 128° C (262°F)
Fuel limiting factor timer at 217 counts below 80° C (176°F)
Fuel limiting factor timer at 169 counts above 80° C (176°F)
Power enrichment at base A/F ratios > 56°C (133°F)
Rich/Lean O2 offset at 16 counts between 20°C (68°F) and 92°C (197.5°F)

Idle Control Functions
Target IAC idle RPM >80°C (176°F)

Miscellaneous Functions
Crappy idle programming begins at 95°C (203°F)

(I just threw that last one in there to lighten your spirits a bit.)

That is only a partial listing, but the significant ones are the mixture control and target idle RPM. At higher temperatures, the target idle RPM is lowered even more. And you may be operating at a CTS point where the target idle reduction is too great for your engine to operate smoothly. It is possible that you are over 95° and the dash gauge is not 100% accurate (It happens). That may explain some of the other ECM functions being active, even though they should occur at a higher than indicated coolant temperature.

 

thanks Vader....so far I haven't come up with the problem, I recently changed intake gaskets, not sure if everything is set up right.

need to check tps, all spark plugs and wires and all other basic stuff. Car runs not bad when cold, also, I was reding that I should be running a stock 195 stat, is that true, I think there's a 165 or 180 in it now.


By the way, it's a '92 5.0 TPI with a 5 speed.