Thedunzelmon

Okay ill keep things short because i have been having issues posting to this forum cause im new here. But my 2004 GT is idling funky when warming up. It surges between 700 and 900 rpm. When driving everything is fine no spitting or missing. No engine codes. Just this unusual idle. The car has an aftermarket intake and throttle body which i have checked and everything is on nice and tight. Thottle position sensor is new. I ordered a new IAC valve and am having trouble to find a new PCV valve for my motor. My car has 82000 miles and never did this until recently and i want to fix it before it gets worse. Is there something i didnt check? Something else it could be? Please help

Z28KLR

What brand IAC did you get? I ask because that is one of the few parts where an oem Motorcraft replacement is generally recommended over the ones that parts stores sell. That may possibly be your issue though, so post back when you get the new one on.

As far as the pcv valve, in my experience they usually do not need to be replaced. Pull it out and spray it with some carb cleaner. If when you shake it the little ball inside rattles freely and there is otherwise no damage (cracks etc) to the outer casing then it's good and can be reinstalled. If you do need a new one, Autozone etc should have it, it's not an uncommon item. You can also check Rockauto.com if local parts stores don't pan out.

Is this idle issue only at warmup?

Thedunzelmon

I did alot of reading around and yes i ordered the OEM motorcraft IAC valve. I got the part off of late model restoration. It should be here around monday or so. As far as the idle goes it does it when it is warming up from a cold start, and it will also do it if say i left it to sit for an hour or so then went to drive it. It won't be completely cooled off, but as it gets to temperature it will surge between 700 and 900 rpm, then smooth out after driving. I am also going to replace the spark plugs coils and injectors soon before they begin to misfire. Ill get back to you once i install the new unit on monday.

Thedunzelmon

I just got the new IAC today and installed it. The initial start was back to normal. it runs up over a grand and then slowly begins to slow down to 1000. Once it fell under though the surge was still there. It wasnt as bad as before or as rapid but it was still noticeable. I read that it could also be the spark plugs and coils, which i already have ordered new plugs and just need a little extra money before i can order new coils. Is there anything else i should check?

Z28KLR

I seriously doubt it's either plugs or coils. If it were misfiring, yes. But surging, I would look at things like a possible vacuum leak. Probably not your problem, but might also be worth investing $6 in a can of MAF cleaner and giving that a try.

Could also be the upstream O2 sensors, but without a check engine light to lead you in that direction or other diagnostic equipment so you could view the data they're producing, I'm not going to recommend just going out and buying new ones for the sake of throwing (expensive) parts at the car.

Could even be EGR related. But again, without the cel coming on to at least lead you in that direction it's pretty tough to make a reasonable conclusion or diagnosis of that.

Thedunzelmon

Alright man I found the problem. It was for a fact the plugs getting ready to go. I was able to take the car to ford for a free full point inspection and they told me that they pulled half the plugs out, and they all looked worn out. But they also found out that my trans needs new internals which is a 1200 dollar fix through them:/ but it is not too serious and will be addressed when i get the extra money i want my car running its best. Thanks for all your help!

Thedunzelmon

The Transmission doesnt need all new internals just a new input shaft bearing but thats a huge job in itself. Goddam 3650's :/

Z28KLR

Just find a used 3650 and swap it in. Or for the money Ford wanted to replace 1 bearing I'm sure you could find a fully rebuilt unit with a warranty.