Slight thumping on idle
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Joined: Jan 2010
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From: USA
Slight thumping on idle
Hi, I have a 97 F150 XL with a 5.4L Tritian and transmission out of a 2000 F250 donor truck. The engine has about 120K miles and has a slight thumping going on when it's idling. It seems to do it once it warms up. You can feel it vibrate when it does but it's not constant and it does it enough to be annoying. I'm thinking it has something to do with the spark plugs or coils but I'm not totally sure. Dad has replaced the coil boots and springs and the coil on the last piston on the passenger side as well as putting conductive grease on both ends of the boots. Any advice would be appreciated, thanks.
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From: USA
no codes or light otherwise we'd be fixing it the next chance we get. by thumping, I guess it could mean it's missing a little bit. it doesn't feel weak or anything, just happens on idle or if you rev it up and keep your foot steady. the rpm will fluctuate instead of keeping a constant speed. idk if that's related. like the tach will drop 200rpm then speed back up and the gauge already reads 200rpm higher but that's not why the rpm of the engine fluctuates. this all happens when it's in park or neutral. it's not as bad when it's in gear but it's there.
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Joined: Sep 2006
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With no codes set you can't tell much more just by observation other than guessing.
It's time to use a Scanner to look the live and stored data.
The first data point is the misfire monitors for each cylinder to detect a faulty coil that is not bad enough to set a code. The misfire count will be high on any offending cylinder.
Next would be to look at the EGR system. If the EVR is leaking any vacuum enough to open the EGR even a small amount, the engine will react to it.
Next is fuel tables and fuel pressure.
Next, any other parameters out of normal range and the causes.
Good luck.
It's time to use a Scanner to look the live and stored data.
The first data point is the misfire monitors for each cylinder to detect a faulty coil that is not bad enough to set a code. The misfire count will be high on any offending cylinder.
Next would be to look at the EGR system. If the EVR is leaking any vacuum enough to open the EGR even a small amount, the engine will react to it.
Next is fuel tables and fuel pressure.
Next, any other parameters out of normal range and the causes.
Good luck.
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