Idle is even worse after Idle air control valve replacement

[mrmoonlight87]

Hey yall. Ive got an 88 with a V6 4L engine swap from a fuel injected 93 explorer that I recently acquired. She idled really high when cold. So I switched out the IAC valve and now she idles horribly, and dies out on first start. I have to sit there and depress the gas pedal while she warms up to keep it from dying. Otherwise the needle jumps up and back down less than 1k RPM and sputters. Any suggestions? I almost want to put the old valve back on! at least she didnt die everytime i started her. I unplugged the negative from the battery terminal trying to reset the computer but that doesnt seem to have solved the problem. Also even when engine is warm now, she will sputter out and die after five min of idling. Thanks in advance you all rock.

 

[bobbywalter]

Test vacuum. What is unhooked....did you bump tps loose or damage it? Vac lines broke or loose? Maf loose? PVC off? New part can be junk.

 

[mrmoonlight87]

I didnt unhook anything other than the valve. It was way easy to access, two screws to back out, switched the gasket and put the new one. No hoses disconnected that i can tell. I really have a feeling this is a computer issue. Like it hasn't gotten used to having a clean IAC valve.

 

[fastpakr]

Put the other valve back in to confirm the new valve as the problem. Return for a replacement if so.

 

[bobbywalter]

Or you knocked loose a chunk of carbon


Probably junk part or the connection bad

 

[Eddo Rogue]

I just went through idle issues on my '93 4.0ohv, which started after I replaced the cam synchro and every gasket/ sensor above the heads (and new injectors)....
Might be a bad throttle body or tps, which u can test voltage for.
Might be be bad/defective IAC...my brand new autozone one was bunk, I replaced it again with a motorcraft unit and problem solved.
Might be a bad MAF, sometimes even if they look clean, they have gone bad.
Might have a broken vacuum line, especially the hard lil plastic tube ones, some of mine looked good, but were cracked along the way.
Pull apart a vacuum line or two, if it doesn't make a difference, you have a leak.
When was the last time pcv valve was replaced? (again get a motorcraft unit, my aftermarket one was junk).
As mentioned, ya might have knocked some carbon loose...and take a good look at your connections/wires.

If you think its computer issue, disconnect the battery for 10-15 mins then re connect and go drive for 20-30 mins (ideally both stop & go city driving and hwy cruising) to let ecu reset/learn parameters.

Idle issues can be quite a cat and mouse chase, hope this helps...