so i got my son an 89 f150 4x4 with the 6cyl and it has a surge during warmup and then also when we drive down the road it feels like it misses every now and then. CK engine light is not on, havent done the normal tuneup yet but going to when i get the bronco out of the garage. anyone have some ideas about the surge at idle. Thought it was the IAC so i changed it out with one i had laying around and it does the same thing. Maybe the TPS?

Thanks

Tim

 

A rolling idle is typically caused by a vacuum leak or a bad TPS. Regardless, always check for codes before spending any money for parts. Yes, you can have stored codes without an active Check Engine Light.

 

Elkarcher171: Check out the following for my two cents:

https://www.ford-trucks.com/forums/1...l#post14967023

 

I dont have a vacumm leak and i havent had a chance to swap out the TPS. Thanks for the help. I will let you know what i find out.

 

How do you know there is no vacuum leak (s)?

What testing did you perform?

Instead of blindly replacing a part why not measure the signal output first? FYI...many aftermarket TPS are bad right out of the box. I highly suggest you measure the one you have. A quick code check may also keep your wallet thicker.