high idle

[prodigy_16]

my father in law has an o1 pontiac montana, and it has a high idle problem, it willl idle between 1500 and 300rpm, but only when the van is moving, when you stop it slowly returns to normal. I know it is not a vacuum leak of some sort because on occasion it will idle normal, if it were vacuum it would be consistant and the high idle only happens when the vehicle is in motion (let off the accelerator and put it in neutral and the idle is between 1500 and 3000) I have removed the line from the cruise, replaced all the sensors (tps, maf ect.) replaced the tb with a salvage one from a ga gt, cleaned the iac, reprogrammed and then replaced and reflashed two pcms, (both flashed with dhp 1.0) and I even replaced the bcm. I have run out of ideas, it throws no codes and gm mechanics say they can find no problems.

Does anyone have any Ideas???

[HayesPerformance]

Question

Do you say. In gear, driving, It will rev Up to between 1500 and 3000 RPM? Even In gear with the brake on????

Let me know.

Regards,
David Hayes@
HAYES PERFORMANCE PLUS

[prodigy_16]

in gear but only while in motion, once you come to a stop the idle returns to normal after a couple seconds, in gear the revs are limited by the trans, but still high, once you bump it into neutral it will rev up to 1500-3000 rpm and stay that way until the vehicle comes to a stop. it confuses the hell out of me.

[SappySE107]

There is a throttle follower in the code to keep the IAC open during vehicle movement. It helps keep the engine from stalling when you let off the throttle. My guess is you either have too much gap around the throttleplate (ultra rare for a stocker), a TB gasket leak, IAC is bad or out of step with the computer.

Do you have any way to scan the computer?

[prodigy_16]

yes, my bro in law workd for dhp, the computer is new (salvage yard new) with a fresh dhp reflash, i replaced the tb and all the sensors, and torqued the tb down good. what should i look for on the scan?

[SappySE107]

Id try a stock flash and see what that does. As far as the scan, look at your IAC counts(steps). Just see how fast it closes when you come to a stop and also what the counts are while its idling high.

[91BerettaGT]

Just to inform you. I had a 2001 Impala with the 3400. It did the same thing however in drive it would move itself. Ended up being Poor information being sent between 2 PCM's and the 1 BCM. 1 PCM was bad and the 1 BCM was bad, the other was saveable and was reflashed by the dealer.

See a thread i made on Domesticcrew.com

http://domesticcrew.com/660board/viewtopic.php?t=1172