Suburban idle issues

[myfirstbonnie]

What controls the idle on my 95 Burb. I know it is supposed to idle up when cold, but idling at 1500 when it is 70* out is a little high. There are also times when I will come to a stop and it will idle around 1000 and slowly drop to 700 after a few seconds. It even does this when the coolant is up to temp. This is running the OBD I yet and does not have an IAT or MAF sensor, but does use a MAP sensor and TPS. The TPS is fairly new and is non-adjustable, but is reading correctly according to my Haynes manual. Does it have a second temp sensor besides the one in the left head? Is it possibly a bad MAP sensor?

Other than that, the truck runs and idles fine.

[willwren]

On my 95, it was primarily controlled by the TPS, believe it or not. I had an idle issue like yours, and it ended up being the tps. Get a meter on that sucker.

[myfirstbonnie]

I have my scan tool. I will monitor it when I take Wendy to work tonight.

[LeSabreUltra]

Hmm, I may be having a similar issue with my S10. Every now and then it'll just seem to have way too much power at idle, and will rev high. Like I'm giving it a little throttle but I'm not. Then it'll calm down after a second.

Then again, my scangauge is constantly reading the TPS value and it's always 0 when I let off the gas I think, so I dunno...
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[myfirstbonnie]

TPS reads fine at .70 volts and transitions fine with acceleration. I am thinking maybe a vacuum leak. My IAC is at 0% and the idle was at 700RPM in gear with no accelerator applied. Doing cold start this morning to see what it does.

[TUFFBONNEVILLE]

just so you know i just picked up a 95 suburban parts truck
so if you need a computer or a part or two just let me know

[myfirstbonnie]

This morning it was a little cool out. Idle was at 1500 and the IAC was reading 129 and slowly came down. By the time I drove the 20 miles there, it still wanted to idle high and the IAC was reading 84.

This time it did show a code 15 for bad coolant sensor input. I did find both coolant sensors. one by the thermostat housing and the other in the left head. Tomorrow I will check to see which one is for the gauge.

[myfirstbonnie]

Problem solved. I checked for vacuum leaks with carb cleaner and found a bad gasket under the EGR valve. New gasket and torqued down tight and idles a lot better.