I've been noticing that my rpm seems to be creeping up without me giving it any gas. It does it real slow from 2000 rpm to 2500 rpm then it levels off(my car's a 5spd TPI) When I rev it it drops down. I thought my tb or linkage was filthy so I sprayed it with TB cleaner. It went away for a few weeks then it came back. Any ideas?

 

check your TPS (throttle position sensor)..maybe it needs to be replaced... or perhaps the throttle cable is kinked and gets stuck at times until you rev it

 

So you guys think the increasing idle speed problem could be due to a faulty tps sensor? Its just weird that it drops back down when I rev it. I've seen them on CARPARTS.com for 50 bucks. I guess it would be an easy fix if that's the cure.

 

Under what conditions does this occur? Cold engine, sitting still, from start up, hot idle, etc.?

 

Usually after its warmed up. Ill be in 2nd gear in traffic, lift off the gas, and have the rpm start creeping up on me.

 

One time I was driving down the street and my car starting pulling hard. I released the clutch and it revved to 5500. So i turned off the car, started it again and it did the same thing. I got out and fiddled with the throttle cable for a bit, started the car up again and it was fine. My throttle cable just was sticky.

 

I had that BS when my MAF needed replacing.

 

Check your TPS with a voltmeter first...don't buy one if it isn't junk.

 

My car is speed density so I dont have a MAF. I'm not too swift with the electronic stuff. How do you check the voltage on the TPS and what would indicate a problem?

 

Not to confuse the issue since the above posts probably have the answer...

However, my 1983 Monte Carlo SS started doing this a few years back. As it turned out, the cruise control unit was going bad and would simply decide to accelerate. Replacing the unit eliminated the problem.

I would check the above recommendations before you look at something as weird as this.

 

Thats funny that you mention that, it feels like im pressing the accell button on the cruise control when it accellerates. Can I just disconnect the cruise from the throttle linkage to check it?

 

Yup, just detach the cruise cable from the throttle linkage.

 

I don't think this is the problem, but make sure the floormat doesn't ram itself underneath the gas pedal.

 

This happens in my IROC as well. But it only happens when I am at idle and the A\C is on. It never does it with the A\C off. I am pretty sure this is normal if the A\C is on as the RPM's are supposed to kick up. Is this what you are reffering to? Just a thought.

Andy

 

No....its just when I'm driving normally...but the car is hot.

How do I check the TPS?

 

TPIterror,

I just found an article on some of the past reported problems with some models of our cars. It had to do with sudden acceleration. I cannot find the fix for it though. It is apparantly something that has been reported to the Center for Auto Safety. It can be found here:

http://www.autosafety.org/autodefects/GM-F-Car.htm

Here is a quote form this site:

"NHTSA investigated all 1985-88s with 5.0/5.7L engines for sudden acceleration but failed to order a recall."


Unfortunatly it does not offer a resolution. I will keep looking though. If I come across a fix, I'll post it here.

BTW - I know yours is a '90, but it may still apply.


Andy