ok guys, I've search around here for a while and can't seem to find the answer to my exact situation:

'94 F250 4x4 7.5L auto with 141k miles on it. I've had it for 2 years now and around April it started to having idling issues only after it fully warmed up. It runs like a top on the road under driving conditions. Whenever it gets to operating temperature, when it's idling, it will oscillate up and down from about 500-900 rpms, then after about a minute doing this it will die. After it dies it will crank back up and then repeat that process. Seems to do this worse when in Neurtral but will still do this at a red light if you're stopped long enough. Also, when you SLIGHTLY open the butterfly off of idle, and i mean SLIGHTLY, it will get worse and then die. If you move the butterlfy normally and run up the rpms it will run fine. So far I've replaced the TPS and ECT with no good results. It's also not throwing a check engine light and I'm not exactly sure how to manually check codes on this truck as I haven't had a problem yet. Truck runs ok, but this is getting on my nerves so I figured I'd ask you experts out there!

Thanks and God Bless.

 

You might want to check the engine coolant temperature sensor. Mine thought it was -34c and would start fine cold but run at 2k rpm after it warmed up and hard to start when warm.

Yours may be stuck with a hotter temp.

 

My 460 powered motorhome has idling issues when really hot due to an advance auto sourced, Chinese made IAC motor. I just need some time to put in the rock auto sourced, usa made, motorcraft unit.

 

Ok, I was wondering about the IAC and IAT, but not really sure of what they do exactly. I did replace the coolant temp sensor, but that didn't help anything. Is there a way to test both the IAC and IAT before I go buy one? I'm not exactly full of $$ and don't like replacing things that work anyway!!

Thanks.