I have a 97 f150 with a 4.6. When I stop and the truck idles down it almost stalls and idles rough. But it drives fine. I had a mechanic friend hook it up to a high end Snap On computer and he says everything is fine but he believes I have an intake leak. No trouble codes and I can't get the rpms to change with ether or propane when sprayed around intake. Should I just put on new intake gaskets? Or start somewhere else? I have never done anything this involved but I have the tools and a clymbers guide. Any help or tips that would simplify this would be appreciated. Thanks

 

That's an IAC problem, most likely.

 

x2 on the IAC issue

 

how do you tell if the iac is bad? I replaced the original about 1.5 years ago and my buddy ran it all the way open manually with his computer and said it was working. Could it have gummed up again that quickly? I had it on a computer about 200 miles ago. thanks

 

It's not that hard to pull and clean. Use Seafoam Deep Creep.

 

IAC motor seems to be working. Tested it with probes everything checked out. Cleaned the MAS and still idles rough. Anyone ever used Sea Foam engine treatment one the vacuum system? Guy at autozone says its like a reverse smoke test. It will clean your vac system and show any leaks, if there are any. He says it works great but smokes terable for a few minutes. Any help?

 

CLEAN the IAC..........

 

X2. Use DeepCreep and compressed air to assist. DON'T suck Seafoam thru the Booster line.

 

this is sea foam engine treatment. Different than deep creep this is a liquid. On the bottle it says how to use it to clean vacuum system and valvetrain.

 

What? Deep Creep is made by Seafoam. Not the same as Seafoam. Deep Creep is in an aerosol spray. It cleans and lubes at the same time, you don't choke the engine with it, cause possible vapor lock and catch your cats on fire.
Deep Creep is a sensor safe cleaner. If you want to shove Seafoam down it's throat, by all means do it, it's your engine.

 

There are people here who swear by sucking Seafoam down the vacuum hose, but I would never do it - if you want a good intake and combustion chamber cleaning, go get a BG or Motorvac job. Seafoam Deep Creep is like a spray penetrating oil. Seafoam down the vacuum hose, if not done very carefully, can cook the cats and even hydrolock the engine. I'll pay the dealer $85 every 3 years or so for a BG job.

 

just got around to cleaning the IAC seems a lot better. We'll have to give it a while. Thanks guys for the help.