Hi all, I have been chasing this noise for a couple of months now, I found this Topic from 2002 today by Mike Mayer, and his description is Identical to my problem (See below). Has any one else run into this and found a fix, I was going to start a tear down of top end until I saw the info about possible bad injector. does any one know mike and how to get a hold of him to see what he found to be the source of this anoying sqyeak/chirp. I was sure it was a rotational squeak until the reference about injector pulse width.
Issue:
"When the engine is cold, I hear a repeating metallic sqeaking or chirping coming from the area of the rear of the engine. This is the
4.0L V6. After about 5-10 min of driving, it goes away. Sometimes, it's gone even forseveral weeks - even when cold.
The chirping goes about 400 - 450 times a minute as the engine is idling at about 800-900 RPM. That tells me the chirping is happening at half crankshaft speed. The spark plugs, fuel injectors, and valves all do their thing at half the speed of crank rotation, so I suppose any are suspect.
Using the ear on the wooden-dowel-against-the-engine trick, I hear nothing inside like a clattering valve or bearing, and no chirping thru the dowel. But can still hear the chirp when just standing there listening.
I listen with the dowel to the injectors and you can clearly hear the rapid tic-tic-tic-tic-tic of the injectors (that's normal). But I don't hear the chirp in the dowel, only from the back of the engine without the dowel, as if it's external to the engine. The ticking of the injectors is in sync to the chirp repeating, so that verified for me that it's at half crank speed. Seems to regular to be a rubbing part on the outside of the engine.
It's not the serpentine belt - we even pulled it off and started the engine for a couple second without the belt - and we still hear the chirping. So that rules out any of the belt-driven accessories and the idler pulley and tensioner, as well ruling out the water pump.
Question is, can a fuel injector squeak? I can't imagine it's the cam or the lifters or the valve guides, as they are all bathed well in oil. Plenty of oil per the dipstick, and plenty of oil pressure per the OP guage. "
Thanks for any clues...
Mike