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New noise

dbltapp

NAXJA Forum User
I was jumping my buddys Ford tonight and heard a new noise. A tapping from I beleive the last cylinder, closest to the fire wall. Last week I noticed my spark plug had worked loose, fixed that, so thats not it. It goes away as you accelerate, should I be concernd? 1996 4.0, auto, 127,000 miles, good oil pressure, syn oil, probably needs to be changed soon. Is this a normal noise? The motor pulls hard, and runs smooth otherwise. Thanks.
 
if it's higher pitched it's a lifter,they are notorious for going bad.mine has piston slap until it's warm(95 ho,167,xxx)and the occasional lifter tick but it's not supposed to be a damaging problem.
 
See if it changes its frequency with slight changes in engine speed. Some later XJ's, of which I think the 96 is the first, have a vacuum operated purge valve on the passenger side firewall which can make a knocking noise that nearly perfectly mimics a failing rod bearing at idle. But it doesn't speed up when idle goes up a little. Listen carefully to the gadgetry hanging on the firewall there, and if there's doubt, unplug the electrical connector on the purge valve to see if it changes anything.

If it isn't that, and if it goes away with speed, and does not reappear or intensify with load, you probably have a ticking lifter. Sometimes that can clear up with a couple of closely spaced oil changes with really good oil.

Piston slap is also common, but that usually will sound more like a general rattly or diesely sound. It will also go away with acceleration, and may also get better when the engine is fully warmed up.
 
Matthew Currie said:
See if it changes its frequency with slight changes in engine speed. Some later XJ's, of which I think the 96 is the first, have a vacuum operated purge valve on the passenger side firewall which can make a knocking noise that nearly perfectly mimics a failing rod bearing at idle. But it doesn't speed up when idle goes up a little. Listen carefully to the gadgetry hanging on the firewall there, and if there's doubt, unplug the electrical connector on the purge valve to see if it changes anything.

If it isn't that, and if it goes away with speed, and does not reappear or intensify with load, you probably have a ticking lifter. Sometimes that can clear up with a couple of closely spaced oil changes with really good oil.

Piston slap is also common, but that usually will sound more like a general rattly or diesely sound. It will also go away with acceleration, and may also get better when the engine is fully warmed up.

Thanx, I will check it all out:repair:
 
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