1992 Culass Ciera S - V6 AT - high idle

DBUCK

MEMBER
1992 OLDSMOBILE CUTLASS
75,000 MILES

Very high idle - replaced iac, no change - dtc codes: 14, 15, 21, 22.
Speedometer not operating until engine warmed up - then fluctuates full scale, sometimes stops, very erratic. No other trouble codes have appeared. Engine cooling fan comes on with high idle.
When trouble first began, only code 15 showed. I replaced the engine coolant sensor - did not help.
Sometimes, after driving warmup, everything smooths out and engine functions properly. After parking a while, car starts in high idle again. Placing shift lever into drive really hammers the transmission with that high idle.
Where is the pcm engine ground located?

3 Replies

WRENCHTECH

MECHANIC
20,758 POSTS

I suspect that you have been unplugging sensors with the key on and that's how some of those codes were set because they are conflicting codes. Clear all your codes and start over to see which ones reset.

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Tuesday, September 6th, 2011 AT 4:45 PM

DBUCK

MEMBER
2 POSTS

You're right - I reset the codes. Now get code 21 indicating the TPS.
Checked the TPS with a digital meter, moving the potentiometer lever very slowly throughout its total range. No glitches or bad spots. Seems to be ok. Voltage levels seem to be ok, too.
The speedometer/tachometer still don't work on startup.
Engine cooling fan also comes on immediately on start-up.
After driving for 3 or 4 minutes, high idle ceases, fan turns off, and most of the time the speedometer/tach start to work, though, intermittently. Car is completely warmed up by this time.
After cool down, high idle comes back.
Grounds seem to be ok.
What's next?

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Wednesday, September 21st, 2011 AT 2:42 PM

WRENCHTECH