Rpm Bounce At Idle

[93ClipseVA]

my car's rpm bounce when im at idle. at first i thought it was just because it was cold, but it would still do this when its warmed up. it'll usually drop under 1k and almost stall but then will kick up higher then come to a medium..like around 1300rpm then it repeats itself. my car has 200,000 miles on it anyway. but has anyone encountered this?

 

[Spydur86]

My 96 n/t has the same exact problem. It's always done it, and I still have no idea why. Good luck with finding an answer though, maybe I can finally get mine fixed as well.

 

[oldman]

my car's rpm bounce when im at idle. at first i thought it was just because it was cold, but it would still do this when its warmed up. it'll usually drop under 1k and almost stall but then will kick up higher then come to a medium..like around 1300rpm then it repeats itself. my car has 200,000 miles on it anyway. but has anyone encountered this?

One thing I would check is the ecu before it's too late.

 

[rjgeier]

ISC. Crebotech.com

 

[Maxximillion]

i have a 92 AWD talon do that to and i had it tested. what happened with mine is the throttle bypass valve was stuck open. and basically what happens when its supposed to work is when its cold this valve will open to let a little more air in when its first starting up with the throttle closed and when its warm enough to run smoothly (judging by what the maf shows) the computer will close the valve and the car will return to a regular idle. when this valve is broken or stuck open it will allow more air into the engine causing it to rev up. when the computer detects this and it confirms its reading 40Hz of air from the maf, it will force it to idle back down. and it will do this cycle until the vavel becomes unstuck or replaced. brand new from mitsubishi the part is obsolete an not in manufacturing so i they told me the cost is about 600 canadian which is ri god damn diculous so i went hunting at a wrecker. problem solved for 5 bucks. hope this helps

Jason.

 

[black92_tsi_awd]

Mine did the same thing...Check the BISS screw. The oring dries out and the screw will back out increasing the idle speed. The ISC goes crazy trying to stabilize the idle.

The oring is a #5 3/8x1/4x1/16. Just screw it all the way in gently and back it out to you get a nice idle around 750. It's worth a try and it's almost free.