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View Full Version : High Idle for 15 seconds only. Then okay.



supercoop
09-13-2009, 10:09 PM
91 SC.

I have searched the forums and found many high idle issues and fix is Replace the AIC.

However, my problem may not be the AIC ?

I press the gas peddle and the RPM's go to about 2,000 and stay there for 15 seconds. Then returns to 900-1000 idle. The car is also running rich but, not at idle. Only when you give it mid to WOT.

Any help would be appreciated. No history on car as I just bought it.

Thanks,

Rob

275hptbirdsc
09-13-2009, 10:48 PM
I had that problem about a week ago thankfully it only lasted a day:rolleyes: Anyway if you havent checked the AIC just go ahead and do it just incase. Also I cant remember where it is but there is a bolt or switch or somthing where you can adjust the idle you should give that a try to.

KMT
09-13-2009, 10:56 PM
Run the codes.....

Spray for vacuum leaks.


Get it warmed up well and see if it does the same thing.

fturner
09-14-2009, 09:24 AM
Better go through the car and see what mods it has done to it such as injectors, TB and MAF etc then list them here. I can think of a few things that would cause that flair but too numerous without knowing more details of the car.

Fraser

BLOWN38
09-14-2009, 11:31 AM
I just bought a car also that had this problem. i found that the cam syncronizer/sensor was 90* off. After I fixed that all was well.

Pretty easy to check the alignment. But it could be a bunch of other things like everyone else says.

MAM
09-14-2009, 02:32 PM
91 SC.

I have searched the forums and found many high idle issues and fix is Replace the AIC.

However, my problem may not be the AIC ?

I press the gas peddle and the RPM's go to about 2,000 and stay there for 15 seconds. Then returns to 900-1000 idle. The car is also running rich but, not at idle. Only when you give it mid to WOT.

Any help would be appreciated. No history on car as I just bought it.

Thanks,

Rob
have you checked for the throttle sticking open? maybe a little bit of carbon keeping it slightly open?i have used a tootbrush with some engine decarb to clean my throtthle body in the past with good results.

supercoop
09-15-2009, 06:05 PM
Thanks for the feedback and suggestions and I will check them this weekend.

Again, THANKS !!

Rob

supercoop
09-20-2009, 06:48 PM
Everything that was suggested previously in this tread checked out okay.


What finally happened after driving the car about 100 miles on short trips was the Air Cleaner started to pulse when the RPM was about 2,500. So I tapped on the various intake / TB sensors.

The idle droppped and then the engine died when I tapped on the sensor next to the Air Cleaner which is in the Air Intake Tube.

Is this the Mass Flow Sensor ?

I started the engine back up and it is working Okay Now !!

Every once in a while the RPM goes below 500 and CE light comes.

BLOWN38
09-20-2009, 09:02 PM
Yes that would be the Mass Air Flow Sensor MAFS. Try cleaning it with brake clean.

supercoop
10-10-2009, 02:15 PM
Yes that would be the Mass Air Flow Sensor MAFS. Try cleaning it with brake clean.

I cleaned it with brake cleaner spray and it works great now.

Thanks for tip.

Rob

Dirtyd0g
10-10-2009, 02:19 PM
I don't like using brake clean I worry about that white residue. I use the spongey alcohol prep pads. It is amazing how much dirt comes off those maf sensors, especially if you use a K&N.
Alan

timsmigill
10-10-2009, 06:39 PM
CRC makes an actual MAF cleaner, I think it is an alcohol based spray. I use it every oil change just to avoid problems from my k&n filter. Just spray the inside of the sensor out good and your all set. I bought it at the local autozone. In the past I just used gumout carb and choke cleaner, which also worked great.