my gf has a 98 mystique and it constantly has problems. . .
the newest of which i'm having trouble diagnosing.
the car idles between 1,000 and 3,000 rpms and makes a strange noise.
it seems as if the car is trying to keep the engine running by idling at a high rpm.
when i barely touch the gas it revs up and holds the rpms for up to 5 seconds before it decends.
the check engine light came on once for a few seconds but almost immediately disappeared.
i'm having some serious trouble figuring out why this is happening.
someone please help.
thanks

 

Is this a double post? please delete it then.

 

Oh, you highjacked another thread... leave this one on and delete your post on the other thread.



Before computers invaded the engine bay everything was easier. Now you have to think why a computer does what it does.
It raised idle on your gf's engine because otherwise it would die.

Which engine? 4 cylinder or 6 cylinder? Mileage?
When was the last tune up performed on this 14 year old car? (airfilter, plugs, wires, coilpack).
Are there any vacuum hoses broken or loose? PCV hose maybe?
Is the MAF sensor clean?

I could go on and on.

 

As bluewind stated there could be a verity of causes for the symptoms you are describing and not a lot of information to help you diagnose them.

In addition to bluewind’s requests I would like add a couple more if I may since he didn't "go on" .

Is this problem present only at start up? Does it persist after the engine is at operating temperature? How does it act while driving, is it normal or does it act up when slowing or at a stop? Do you hear a hissing noise under the hood? When you press the gas pedal does it seem sticky at the top? Open the air filter box, is there oil in the breather tube?

Many times information thought insignificant to the owner would help eliminate a large number of checks.