Fast Idle

[CaptnHoke]

Help! I've been building on my 87 K5 and have an extremely high idle problem. I've installed a late model 350 with Vortec heads and a Comp Cams 270 HR cam. We used GM TBI intake manifold made for this upgrade, have replaced all sensors, checked thoroughly for vacuum leaks, put in Motorvations prom chip for this and the engine seems to run great except for idle. At start up all is well, but after driving a while the idle seems to climb to the point that when you shift from drive to park the engine is racing, maybe 1700-2000 rpms. If I then shut off the ignition and immediately restart, the idle is fine and seems normal. I am at wits end and cannot find the problem! Any help would be GREATLY appreciated!

 

[Skweegle89]

How did you thoroughly check for vacuum leaks?


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[CaptnHoke]

I Have replaced most vacuum lines and the. With the engine running disconnected each and noticed the change in rpms. I've also sprayed starter fluid around and have gotten no change or increase in rpms

 

[bucket]

When you restart it and it's idling close to the correct speed, unplug the Idle Air Control Valve and drive it around a bit. If the idle doesn't climb, you've found that you have an IAC valve problem.

 

[bucket]

Or does it only raise up after a cold start? If so, are you letting it sit and idle the whole time? Or are you driving it?

 

[CaptnHoke]

Thanks for the advice. I did a reset by jumping a&ab on the ALDL port but haven't had much time to try anything else. Weather is going to be warm this weekend and I'll delve into it further