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Old 04-05-2009, 05:50 PM
Join Date: Jul 2008
Location: Anchorage, Ak
Vehicle: 2002 Ford F250
Posts: 59
My take on the infamous knocking noise at idle & pinging under loads...

I'm hoping I may be correct on my year long search for the fix of the knocking noise at idle, which almost sounds like a quiet deeper sounding rod knock. And also the pinging problems alot of people have been having.

I believe they are caused by the same problem...

Caked carbon & oil on the pistons, walls and valves.
Everyone knows that carbon build up will cause pinging due to the extra compression in the cylinders but is anyone aware that this oil/carbon build up will cause knocking noise at idle??? (sounds very similar to rod knock at idle but has a little deeper tone also may be refered to diesel noise) Especially noticeable when pulled up to a drive thru or next to any building.
The knock also does not go away when engine is warm.

I personally used a mirror to look into the bottom of my intake manifold and found something that shocked me... a pool of oil from none other then the PCV system. This is even with a new PCV. So I know oil vapor is getting into the cylinders and most likely caking up.

Did alot of searching and finally stumbled on some information of the caked oil causing engines to sound almost exactly like rod knock at idle but just a little deeper sounding. I believe the explanation was something about a shockwave making the noise just like pinging does.

My plan of action is do the throttle body, TB elbow, & intake manifold cleaning followed by a decarbon procedure with seafoam. And probably some BG44 in the gas tank. Hopefully and finally making an oil trap so this doesn't happen all over again.

Has anyone else had this combo. of problems?
And am I on track with my thoughts on this caked oil problem causing rod knock noise during idle?
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Old 04-05-2009, 05:50 PM


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