This is on my 90 lumina 3.1 Automatic. I'll be doing 70 75 for a while and I'll let off the gas and the car will continue to stay at that speed unless i tap the breaks fast. Any Suggs? Car has 129,000 on it but runs like a top.

 

Check the throttle return spring, I'm guessing FI cars use a spring. Make sure it isn't kinked. This happened to me on the highway full throttle stuck going 60mph, that was some scary $hit.

 

Just a guess...

A short in the cruise control? (If so equipped.)

 

That makes sense.

 

There is a fairly well documented (60 Minutes or Dateline) set of known failures in cruise control units in cars of that vintage. Apparently, when moisture gets in the cruise units, it begins to corrode the connectors and they have a tendency to short.

My 83 Monte Carlo SS did this only it started doing it all of the time. I really had to jump on the brakes a few times at stop lights a few times! I replaced the unit and never had the problem again.

Could be the problem...

 

check for carbon on the throttle plate too they usually stick closed though but hey what the hell it could do it then too

 

Carbon i nthe plates is all cleaned out before this. HMM I did use the cruise control the night before. I'll have to check that out.

 

Check the Idle Air Control valve if it has one. My father in-laws Jeep would do this alot. When you start it up does it idle up high. The Jeep would and you could turn it off and then back on and it would be fine. Sometimes it would just start idleing up when going down the street. It makes it hard to stop.