My 2001 EXT Cab F-150 has recently started having a rough idle at intermittnet periods. Also there appears to be a whining or whirring noise under the hood when it is running rough. The tach does not fluctuate when it is doing it and strange thing is that you may go to next stop and idle is smooth. Usually start after warmed up and not cold. Ford dealer says no codes show up or stored in memory and that this is normal for 5.4's. This is driving me nuts. Any help is truely appreciated.

 

I'll take it by the dealer's answer that it has the stock xhst system on it.

My truck does the same thing, so I think it is time to check the IAC on it.

If you do a search on IAC, you will find the procedure for cleaning the IAC. It is the cylinder looking metal part on the back of the throttle body elbow.

I had a case about 18 months ago where mine in very cold weather would stall. Took off the IAC cleaned it, and put it back on, stall gone.

You other one might be a cracked rubber 90* for the PCV hose from the back of the Throttle body elbow. ??

This time I am trying JMC's suggestion of taking the whole Throttle body elbow off, the intake, and then removing the IAC, got to work better then off-sets and 90* drivers

The rough idle could just be a case of the engine wither not getting enough air via the IAC, or it is getting too much air and adjusting for it, causing the rough idle.

Good luck

 

Thanks alot Scully, that gives me something to go on. Looks like alot of IAC problems. I still have about 2 months of warranty left so I am gonna take it back to them again with the IAC possibility. Thanks again. Take care.