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At low rpm`s, especially in drive with foot on brake , there is a thumping noise coming from the right center engine area.there is also rapid fluctuation of my oil [pressure guage.
This all stops when i apply gas or put it in neutral.
Otherwise the truck runs great.
Good question. I was about to search the exactly the same symptoms. Also a 97 4.2. I did an oil change and used a flush - problem went away for about 2 weeks then returned.
5\14\07
no signs of white smoke,antifreeze in oil or loss of coolant !
looks like to lowerintake gasket was replaced wit a thick plastic gasket that sticks out on the sides.
I might try heavier oil, like 10\40 or 20\50.
hi joe, oil pressure sender may be on the way out so if posable get a machanical oil gauge rigged-up as a double check. the standard truck high low gauge only tells that the pressure has gone over 7psi.
as for the noise it has chance to be linked to the drop in pressure. again good luck and do not forget the 4,2 engine forum for help. bokker.