94 high idle issue

[thcscubajohn]

Hello, I've been having this problem for a few months now and I can't figure it out. The truck idles really high. When I drive it will idle around 2k. Sometimes it idles at just over 1k. I'm thinking maybe the IACV. When I start it cold I will idle ok, 14-1500 and then come down to like 900-850 but as soon as I apply any throttle it's like 1100 rpm min.

Diagnostic steps performed;

Used parts cleaner spray on all vacuum/air hoses and connections with no change to idle.

Unplugged MAF during symptom of 2k idle, stall.

Unplugged TPS during 2k idle, no change

Unplugged IACV during 2k, no change

Drove with IACV Unplugged, symptoms are less present, more constant ~1k idle, able to get 2k idle to come down with quick throttle jab.

Cold start with disconnected IACV, 600-700 idle, plugged in, came up to 2k, dropped back to 1000

If I slam the hood when it's idling at like 1k it will jump up to 2k and with the IACV plugged in stay there, without it will slowly come back down.

IACV is new, I replaced it after having this problem maybe a year ago and it never fixed the issue

Thanks

 

[jcook100]

I am having a similar issue with my 91 4.0. I replaced the PCV valve and IAC valve with no improvement. Mine idles around 1600.