common vacuum leak locations.

[fourwheelford]

Can you guys give me some info on where the most common places for a vacuum leak might happen on these trucks? My truck idles at 1000 most of the time but sometimes idles at like 800 and seems to run just fine that way, im pretty sure the high idle is caused by a leak but I cannot find one. It just doesn't seem like there are that many places that cause a vacuum leak. Thanks everyone. I was thinking an injector o-ring under the plenum that I can't spray with carb cleaner, or maybe upper intake plenum gasket but I don't know, thanks guys.

 

[Rearanger]

I can't say what's most common, but the PCV hose connection to intake may be worth checking. After my year Ford uses a hose clamp for the outer hose to intake connection, I guess that had given problems in the past. I have already put a spring clamp there. Does the idle get unstable as well?

 

[JP02XLT]

You can easily use a small unlight propane torch to easily find the leak by following the hoses with the gas turned on the torch (not Lit) any fluctuation in rpm will mean it is sucking in the propane & a leak.

JP02XLT

 

[fourwheelford]

Not really unstable it just fluctuates sometimes, not surging but it will be 800 for awhile and then it will be 1000 for the rest of the time im driving. The idle is otherwise pretty smooth, it will shake a bit every now and then but nothing serious.