I know that there have been others with the same problem. 94 5.0L AOD 4x4.

Truck will idle fine until in gear. While sitting at a light in drive the idle will hold fine for about 15 seconds, then it will dip pretty low surge back up, and continue a few times before it finally settles on a very low idle. Low enough that it shakes the truck. Last night had my wipers, headlights, blinker, blower, and radio on, it did what I mentioned above then died. This has been going on for a while now and is really quite annoying. It will do it when first started, and driven before warm. True story, a blind lady with a service dog was crossing the intersection in front of me when it surged! Bet she thought I was being an ***.

Replaced the IAC, TPS, Alternator, PCV valve, Battery is less than a year old, plugs, wires, cap, rotor, cleaned the TB, and MAF sensor also. Your thoughts are appreciated. Thanks

 

Are your spark plugs motorcraft or autolite? If not, you will have problems.

 

I had that thought. I believe that I put Delcos in around Thanksgiving. I've read that most recommend the Motocraft plugs, or coppers.

 

Still sounds like an IAC problem. If the IAC is new, clean the intake manifold, use a wire brush, and some carb cleaner near the butterfly. Remove the IAC and clean down in the portways there too. Disconnect your battery while you're working on it to clear the memory in the computer and then give it a go.

 

When I did the TPS I did reclean the intake, and the IAC. Still the exact same problem. Did this probably about a month ago.

 

Is the IAC valve new or did you just clean the old one? I cleaned my old one and it still didnt work. I bought a new one and seafoamed the intake before installing it. Then I changed the spark plugs and mine ran great after. Could also be a vacuum leak but I think you would notice if that were the case.

 

No the IAC is new. Probably two, or three months old. Then when it still had the problem, a tech told me to try the TPS. When I replaced that and had the throttle body off is when I clean the IAC.

I dont' know about the seafoam. I have 175k, and seafoaming the truck kind of scares me a bit. Breaking loose sludge, and the consequences that can arise.

I thought about just replacing all the vacuum hoses, but I don't hear any leaks. Might spray some carb clean on the hoses and see what happens.

 

My truck has quite a bit of miles on it too, but I think the seafoam really helped. There won't be any sludge if you don't put it in the oil. I did it through the brake booster so it just cleaned the top end.
Check for engine codes if you haven't though. You can have them even if there's no light on.

 

I'm sure that I can use the scanner here at work. I might do the sea foam. I live in an apartment, so I can't imagine them being too thrilled with a cloud of white smoke!

 

Walmart parking lot at night? it is most definitely a lot of smoke. Everyone says it was more than they expected, and I never fully gave that statement credit until I did it.

Depending on what the codes say it could be a problem with the egr being stuck. It sounds like that's one of the only parts you haven't replaced so far. That will definitely store a code if it's the case.