Idling problem

[91GPSTE]

I've got a problem with my 91'. When I put it in overdrive the car idles roughly. I can see the needle moving from about 800 to 500 rpm. I checked the codes and there aren't any. I replaced the EGR and still nothing. Anyone know what could be causing this. In the morning when I put it in gear it actually died.

[91GPSTE]

Here is an update. I replaced the EGR with another one that I had and still nothing. Pulled the IAC and cleaned it. Plugged it back in but didn't attach the vac hoses or screw it back on, tried starting the car. It started but I heard a popping sound so I quickly shut it off. Then put the IAC back in place and started it again and everything worked like before but Service Engine light came on. Still the same idling problem. I pulled the codes, this time got a code 33 which is a MAP sensor voltage low or low idle. I am guessing it come up because the idle sucks because the MIL light goes off when I am driving on higher RPMs. So anyone know what could cause this?

 

Oh and I did the idle excercise listed in the FAQ section and it didn't help.

[GP1138]

When the car is on, tap the MAP sensor and if the idle fluctuates, it's bad.

 

I'd also run a can of STP fuel injector cleaner through it at your next fill-up.

 

Does it do it if you just put it in Drive/3?

[91GPSTE]

I think it does it regadless of which gear.

[GP1138]

Ok. I had a Grand Prix that I was troubleshooting for someone that when I turned Second Gear Start on, it would just die. I ran some STP through it and it seemed to help.

 

Did you tap on the MAP sensor?

[91GPSTE]

Will try the tapping in a few.

 

I run fuel injector cleaner through it quite often though so I doubt it's injectors.

[91GPSTE]

Did the tapping and nothing. Also noticed that sometimes it would jump to around 2000 before dropping down on the start.

[DaveFromColorado]

does it do this EVERY time you stop, or only when it's cold? if it's only when it's cold the problem may be that your TCC solenoid may be stuck slightly open, or worn allowing some fluid to pass by it causing the extra drag on the engine when it's in gear - just enough pressure on the TCC clutch to drag a bit, but not cause tons of drivability issues - not sure how you would test this exactly, becuse if it's allowing fluid to pass all the time, unplugging it simply wouldn't erase the symptom. The reason it wouldn't do this when it's hot is because there's enough heat to allow more slippage in the TCC clutch.

 

--Dave.

[91GPSTE]

Does it all the time regardless if it's cold or hot.