1991 Nissan D21 KA24E - High Idle

[RDY4WAR]

My 1991 Nissan D21 with the KA24E has an issue with a high idle around 1200 rpm whether it's cold or warm. When I unplug the idle air control valve, the idle drops to a more normal 700 rpm but misfires and sputters like it doesn't want to run well. Is the IAC the fault here or am I looking at more like a vacuum leak. Note that it sat up in a barn for 4.5 years before I pulled it out and got it back running.

 

[mk378]

Don't trust a dash tach to measure idle speed.

If it has a modern EFI system, the computer controls idle speed based on the temperature reported by the coolant temperature sensor. If sensor is bad or unplugged it will think the engine is cold all the time and command the IAC to open and make it idle fast.

 

[Falcon_LS]

Does this engine have a Fast Idle Valve Solenoid?

 

[RedSpider]

I don't remember if the E uses the same throttle position sensor as the DE but when my DE was doing the same thing, that's what was causing it.