Well I thought that I had my fast idle problem fixed but it's back again. What is happening is when I first start my truck up it idles fine around 800 rpm's or so. But let's say I am going down the road 25-30 mph I can let off the gas and the rpms will stay the same. A couple of times I even threw the truck up into neutral and the rpm's would slightly increase and stay that way. So I could be at a complete stop with my truck in neutral and the engine is still turning 2000 rpms. All that I have to do is just stab the gas pedal real quick and then the idle will drop back down to 800 rpms. Anyone know what could be causing this? Could it be the IAC valve? Once while it was idling high I unplugged the IAC valve and the rpm's dropped way down and then when I plugged it back up the truck went right back to the normal 800 rpms. Do you think the IAC valve could be bad? I also thought maybe the throttle body blade wasn't closing all the way but I closed it by hand while it was idling fast and it made no change at all. Any suggestions?

 

Sounds like a malfunctioning/erratic IAC or maybe it's just dirty? Have you tried cleaning it yet?

 

Nope I haven't took it of yet to see if it's dirty. I will do that tomorrow to see if it helps. Is there any way to tell if the IAC is bad?

 

This is a way you can clean it with pics courtesy of Rob02
https://www.f150online.com/forums/sh...light=cleaning

Here's Sal's take on a bad IAC:

https://www.f150online.com/forums/sh...ghlight=IAC%2A

According to Sal, usually you'll hear a ticking if it starts malfunctioning (and it's not just dirty)...

 

Hank, out of curiosity, has your PCM ever been reflahed?

Not that this applies, but my SVT Focus sufferent from high idling and they reflashed the pcm and all is well. Im just wondering if yours was reflashed if it would solve your problems. I dont think you have enough mileage on your truck to have a sticking IAC valve.

 

No, my PCM has never been reflashed. Do you think my chip could have anything to do with my high idling problem? My truck has 13,500 miles on it so the IAC shouldn't be bad but if I unplug it and plug it back up it fixes my idling problem. So I may just replace it to see if it is the problem. Will a bad IAC cause the rpm's to not drop back down while driving?

 

Could be a frayed throttle cable. My other truck did that, and when you would stab the throttle it came back down. just a thought

 

Any other ideas guys? What could keep the idle at around 2000 rpm's while driving down the road with my foot off the gas? Then if I just stab the gas pedal real quick the idle will return to normal. Does the IAC valve control this?

 

Hank you saw the pictures,
it takes less than 10 minutes start to finish to take off, clean, and re-install the IAC --> AKA --> IDLE ADJUSTMENT CONTROL.
OF COURSE IT MIGHT AND CAN HAVE SOMETHING TO DO WITH IT. And BTW mine was giving me trouble with under 10k on it. I hear it's a known problem on Mustangs and Lightnings and I would also check the cable like krueger said. Mine has been frayed since day one. One day I'll have to order a new one and change it

 

Thanks Rob, I will clean the IAC tomorrow and see if that clears up my idle problem.