Please note: this applies to the 5.4L engine only.
This is my second write up here on FTE. With numerous posts popping up on engines idling rough, stalling out at a stop, or RPMs jumping, I figured I'd explain how to clean Idle Air Control (IAC) valve. From a few searches here, the IAC becomes carboned up and gunky over time and the little spring inside the housing starts to stick. The result is the rough idle as the engine isn't receiving the appropriate amount of air through the intake. Hopefully this will help solve your idle issues. If not the IAC could need to be replaced or you might have a bigger issue with your truck. But, this job is easy so I recommend trying it before taking it to a shop and paying someone big money to diagnose the problem.
While my truck was and is running like a top I did notice that on cold start-ups, as soon as I'd put the transmission in reverse and holding the break, I'd feel some pulsating in the wheel. It wasn't enough to stall the engine but it was on my mind. After double-checking all my hoses and vacuum lines, I narrowed it down to the IAC being dirty. I figured it wasn't too bad because once the engine came up to operating temperature everything smoothed out.
On a scale of 1 to 10 this is a 3. Time spent on this project was one hour. The most difficult part of this job was loosening the two 8mm bolts holding the IAC valve to the intake. They were pretty tight from the factory and the lower bolt actually required me to use a breaker bar just to pop it loose! Once the bolts are free, the rest of the job can be completed with a standard 1/4" ratchet and shallow 8mm socket.
Tools & Materials needed:
1/4" drive ratchet
8mm shallow socket
1/4" universal joint (depending on your ratchet you might need one to get the bottom bolt off)
Clean rag to wipe off carbon build up on IAC valve
Breaker bar (again to break the bolts loose if you can't do it by hand with a ratchet)
Step 1: Locate the IAC
Step 2: Loosen 8mm bolts
Note: Both 8mm bolts have washers on them so be extra careful when removing the bolts as a bolt or washer could drop down through the intake manifold making it extremely difficult to fish them out. Secondly there is a gasket between the IAC and the manifold. This is reusable but be careful not to drop this or damage it either.
Step 3: Disconnect wiring harness
I didn't snap a photo of this but it's super simple. Once the IAC is free, pull the housing out. This will bring the wiring harness closer and it will be a lot easier to disconnect the plug.
Step 4: Clean the IAC with carb cleaner
Again, no photos but this is self-explainable. Look inside the IAC and it should be black or dark grey from the carbon and gunk build-up. Spray it out real good with carb cleaner (my fluid came out yellowish right away), fill it up and let it soak for a few minutes, then empty it out. You can take a toothbrush and scrub lightly and loosen excess build up and hose out the housing again. Take a small screw driver and make sure the spring can move freely in the housing. Once it does, wipe it off with your clean rag and reinstall the IAC.
Here is the IAC valve:
Step 5: Reinstall the IAC valve
This is easy as well. When bolting everything back up here is my recommendation:
1. Place the top 8mm bolt through the IAC housing and the gasket on the other side.
2. Start threading the top 8mm bolt first so the IAC can hang on the manifold on its own. This will free up your hands so you can line up and thread in the lower 8mm bolt.
3. Thread the 8mm bolts back up by hand ensuring proper installation. Once bolts are snug, use your 1/4" ratchet and 8mm socket to snug the bolts back up. Once snug, give it a final tug to make sure the gasket seals good.
4. Reconnect the plug on the back of the IAC.
Step 6: Relax - you are finished and hopefully have a smooth running truck again.
Hope this helps,
Last edited by 97ExpGuy; 07-02-2010 at 11:07 AM.
Reason: Spelling and word choice
Thanks for a great write up, now I can attempt this confidently. Ive had doing this on my mind for a couple weeks now. Ive got a slight skip at idle so I think this might solve my issue, since I have all new cops, plugs, and FF.
'00 Expy Eddie 5.4 4x4
Edge Evolution CS
Thanks 97expguy, my 1999 ford f-150 would start up and die, then restart, it would usually be ok..but the other day in traffic, it died at stop sign, and took two more starts to get it going..I looked up your reference, and cleaned the iac valve as you said, and it took care of the problem!..thanks again.. Whicker
WOuld this possibly fix my Surging idle issue?
I have a 97 with a 5.4, and when idling, say through a parking lot or something, the truck surges, and lunges... I cant really drive very slow without this happening.
thought of replacing the TPS, but not the IAC motor...
Thanks for the positive comments. I haven't been on the forums in a while as I bought a new toy and that's been occupying my time.
Zigman, give it a shot and clean the IAC. If it doesn't fix the problem, then all you have spent is an hour of your time and bottle of carb cleaner. Plus, it narrows down the possibilities of what is causing your problem. The only other thing I can think of is checking the air filter and cleaning the MAF sensor. If those things don't fix your issue, then I'd type up a detailed post and report back here.
Whicker, I appreciate the positive feedback. What you have described in your post is what most people post about when they have idle issues.
Your welcome expguy...I had no idea where to start looking, thought maybe it was to much oil on the k&n filter, but not so...so I went to the internet,thanks for posting the fix!..Probably saved me at least 150 bux at ford..thanks again. whick
I have a 2003 Expedition that has a crapy idle when you first start it, and sometimes it dies. I'm going to try cleaning or replacing the IAC and see what happens.
Update: Well this all sounded really easy until I removed the shoud and saw that the IAC was on the back side of the intake manifold, about 4 inches back under the firewall. The motor in his 2003 rig sits way back. While I can see the two bolts, they screw in from the back to boot. . That means you must get behind the IAC which is behind everything else, and there is no room to get your hands in there! I bet getting to the electrical plug would be hard too. This is a case of a easy job turned into a nightmare because of crappy engineering. I called Ford and they want $125. in labor to swap it out, with me providing the part. They claim it will take less than 1 hour and they will test everything. I asked how they get to it, well Ford makes a special tool, of course, which we can't buy.
I'm taking it in tomorrow to have Ford do it. What a bummer, as I was looking forward to simple job and also hopiing to save that labor $$$.
"I asked how they get to it, well Ford makes a special tool, of course, which we can't buy."
I have lots of "special tools" you can't buy. I made them for hard to reach areas using a torch, grinder, vise, and hammer. Best of all, they are practically free!
The greatest pleasure in life is doing what people say you cannot do.
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