changed out my IAC and TPS now the truck has an erratic idle. Runs at 1250 and down to 900 keeps surging like that. It is a 1987 302. Any help will be great thanks

 

Did you mark the orientation of the TPS before replacing it and make sure that it was in the same position as the original?

 

Yep, you might need to adjust your TPS.

Take your throttle body back off, loosen the two tps screws slightly and slide the TPS back the other way and tighten them back down.

It will only slide a little bit, but it needs to be slid towards the direction that is away from the direction that has resistance. I have seen cases where someone had to take a file to the screw holes on the TPS and elongate the holes so that the TPS would fall back under 1.0V.

Also, what brand is your IAC? I won't sit here and tell you Motorcraft only, but I have used a brand on my truck that was garbage.

 

Second to that - sometimes new parts aren't perfect. You can try the old TPS and see if there's any difference ?

 

took the throttle body back off and put a dvom on the TPS to put in range, unhooked the battery to clear codes put it back together and all is good! The lesson I learned is to come here first to read up on what others are having problems with so I only have to do it once instead of working on it then coming here to find help on fixing the problem i had and have created by not doing it right the first time.

 

Oh so true, a little knowledge is a dangerous thing. The right knowledge makes life so much easier.