Hey guys. My 1990 5.0 Mustang Lx seems to surge betweem 500 and 1000 RPM at idle. (tacometer bounces up and down) What is the cause of this, and more importantly how canthis problembe fixed? If someone could answer this question for meand how to fix it with the best possible explanation that would be really awesome. Thanks for taking the time to read my post! Thanks.

Chef

run a koer test and check for codes ..after that check for vaccum leaks and then after that clean IAC motor and throttle body;)

It took me almost a year to find the problem.... vacuum leaks were mine. The lower intake was not sealed. Took a smoke test to find it. Good luck and hang in there - follow what these guys tell you and you will figure it out.

def sounds like a vaccumm leak somewhere.

Check your tps too. It should read between about.96-.99 volts at idle.

Suggestions:

DIY KOEO/KOER/Cylinder Balance Self-Test (http://myshifter.com/joel50/EECTEST.html)

Base Idle Reset Procedure (http://tinyurl.com/26ytl2)


ORIGINAL: sethta

Check your tps too. It should read between about.96-.99 volts at idle.


Nope.... as long as the TPS is between .7 - 1.0 vdc, it'll work fine.