Rough Idle

[SeaLion]

Update. I just noticed that if you turn the steering wheel slightly when stopped, it makes the vibration disappear. Could it be the power steering? Whoever else has this vibration, try to move the wheel and see if it goes away on yours too.

 

[parkrw]

My dad had a F-150 w/ the 5.4L engine. He called me and told me that his truck was idling rough. We started troubleshooting the idle ctrl valve etc... Lots of other things. Come to find out, there was a small vacuum leak at a hose going from the pcv valve, Y'ed off to the back of the intake manifold. At the back of the manifold the hose was cracked with a small enough hole that you couldn't hear the leak. I replaced the hose and that took care of the problem. The truck ran like you described your's. The engine heat made the rubber expand and the hole get big enough to cause the problem. A/C affected this too. I don't know if this will help you. Just an idea.

 

[davrober]

I noticed it too today an an 99 expy I just pucked up this morning. A slight slight vibration but rpm is rock steady. I opened the hood and heard a little hissing noise that slowly subsided Id suggest shutting it off and opening the hood right away and see if you hear the noise I think it may be vacume . Its on the pass side of the engine block somewhere in the middle to rear.

 

[green03]

Not saying that this is the solution to anyone's problem but if the airfilter gets dirty (almost plugged) on these trucks it will idle rough. It starts adding timing (instead of adding more air) to bump up the idle speed and you will notice a shaky idle.
Always check the basics first.....
Matt R