My wife has a 98 Malibu with a 6 cyl. The car will start fine after a long off period. Then, for no reason, the engine will go into a high rev situation. It goes to about 3000 to 3500 RPM in idle. Before, turning the car off then on again cured the problem but not anymore. It stays in a high rev untill an extended off period. I thought it might be the cruise control but the lever for that is against the low stop. The check engine light does not come on except after an extended period of high rev.

I'm not very good with cars except for the easy stuff, tune ups, replace rotors, that kind of stuff. I have replaced valves in a 351 cleveland with the help of a Chiltons so I'm not afraid of working. I'm just hoping it doesn't go that far.

 

I've also got a 98 and I just did my lower intake manifold. I put everything back together now it is doing the same thing (keeps reving between 3500-4000 rpm). Can anyone help?

 

I doubt the cruise control would have any affect on this this since it needs two things to engage:
1 - out of park
2 - speed signal

There could be a problem with the MAF , IAV , engine temperature sensor, TPSetc.

You should have the problem codes read to point in you the direction.

 

Thanks golfer. You pointed me in the right direction. It ended up being a stupid mistake on my part. When I put the support bracket for throttle cables back on I didn't do it straight and it was forcing the throttle body open. Once I fixed that everything was all good. Now I just have to look at the tranny fluid leak and it should be good to go. .

Thanks again

 

Yeah... I know the feeling when your in a hurry to put it all back together.

Glad you got it sorted ... thanks for the update.

 

It turns out that it was onlydirty intake sensors. I started at the air filter and started to take the different sections loose and clean the sensors with intake cleaner. Be careful because there are some sensitive components in there. When I got to the manifold I started to put it all back together. It works fine now. I was told to be sure to use intake cleaner and not carb cleaner.

 

Glad you got it sorted and thanks for the update ...Tex .