Mrwykel

I am having a problem with my 86 mustang gt the motor is basically stock just a couple bolt on additions air intake and such. Anyways when the car starts up cold it runs fine after 10 mins or so when it gets warmed up it starts chuggin at idle. It jumps really high then falls really low i have changed the plugs and wires got a new battery changed my fuel filter cleaned my throttle intake valve canceled my egr and the problem still exsists i cannot figure it out for the life of me when i get it into gear and push on the gas it runs fine but after its warm and i push on the clutch it just dies or if it doesnt die and im stopped the idle just bounces up and down kinda like its chuggin i ccant figure it out im thinking maybe an o2 sensor but im not sure any info would help. Thanks!!!!

Link to video showing what the car is doing after its warmed up

Mrwykel

Its a 5.0 btw

AAX86

That, my friend, is the infamous "surging idle" that plagues many 5.0's. It could be a number of things.

Here: http://www.muscularmustangs.com/iac.php

That's the first part of 5 or so popular causes of surging idle problems. I had a really bad surging idle problem not too long ago on my '86. I tried everything and couldn't figure it out. It turned out to be the TPS (was showing 2x the amount of normal voltage). Went to O'reilly's, got a new one for $35 and haven't had any idle problems since. So i'd say check the TPS voltage first of all.

Don't try to get the tps at .98v though, you'll be wasting your time. It's fine anywhere between 0.4v and 1.0v