E250 1988 - random fast idle - can't clear to normal RPM. Need Help!
 

Hello Again... Most of my problems have been repaired, with Hanky's help. One more. After warm up (Thermo open) issue. I get this very fast idle and hit the gas and reving up to kick off as in MOPAR choke warming clear. After return to idle position... it still is idleing fas, maybe 1500 RPMs. I done about all I know... I feel that there might be a mechanical sticking issue with the kick down or throttle cable but it seems to move smoothly. I'm at the end of my ideas... Need some Senior FORD help, here!
Thanks!

Hi Bill,
It is very possible , if the throttle linkage is free to move through it's entire range of travel, that you are working with a vacuum leak. What may be happening is the extra air is getting in there and the computer adds fuel to overcome a lean mixture and so the idle speed goes up.
Check for any cracked or vacuum hoses that may have come off. Don't forget the PCV hose & valve , the hose that goes to the brake booster and any place additional air can get into the engine from the throttle body on back to the intake manifold.

I had a similar problem and it turned out to be a wiring harness that was off it's mount and hanging down into the throttle linkage. My idle was so high I could cruise at 45 MPH with my foot off the gas. I tried stomping the pedal and it almost killed me because I was in traffic and the engine stuck at full throttle. I had to think quick and turn off the ignition to kill the engine after which I coasted off to the side of the road.

Found a few more....
 

I search a Ford Truck sie / site and these suggestions helped:
1. replaced PVC valve.
2. raplaced radiator pressure cap (12 psi)
I got a cold about 750 rpm idle! so happy about that.
When warm i get about 850, these are estimates as I don't have tach.
Waiting for pay day to buy some fuel and do a road test. I believe I got it after my one year of ownership. I'll keep you all informed.

Where is my A/C cycle Switch?
 

Hello all! I'm one the next issue with my 1988 e250. A/C system and wiring. wher is the cycling switch? I search but only found a sw on the dryer unit my schematic indicates another sensor?
Thanks for your help.
BilldarrAZ (Tucson):)

The switch on the dryer is the cycling switch.
Is there some particular reason you are looking for it?

Yes, I fail to see what the A/C low pressure switch for the compressor clutch has to with an intermittent high idle problem???

When an additional load is placed on an idling engine The PCM is supposed to raise the idle speed to prevent a possible stall.