So, I have a knocking kind of noise coming from the engine. It is a deep rhythmic noise that sounds like a hammer banging a table a little more than once a second at idle. It increases in frequency when I increase the revs. I've drained the oil to look for metal shavings, and I didn't see any on the drain plug of in the oil. I fished around with a coat hanger to see if there were any big ones that didn't drain, and nothing.

So I don't think I have spun a bearing which was my first thought.

I also pulled the plugs and they are burnt black.

Does any of this sound familiar? I did a search, but didn't turn anything up.

I'm kind of

I should mention that it is a 1986 944NA. I've recently redone all the vacuum lines, it hasn't overheated, it maintains oil pressure, I don't see any coolant leaks, and I'm a little puzzled why it is running rich, too.

 

Take the accessory belts off and see if that makes a difference. A bad bearing on the alternator could be the culprit. I heard one that sounded like a clutch problem, but was only a bad alternator.

 

I'll give that a try. I did tighten the alternator belt the day before the noise started.

 

Could be the culprit. Couldn't hurt to give your timing and balance shaft belts a look at, since you are going to have the other belts off anyway. They could be slapping the timing case cover if they are loose.

 

Well, I took off the accessory belt and checked the timing and balance shaft belts. No difference with the accessory belt on or off, and the engine timing is still lining up with the marks. I can't see any belt obstructions.

Any other suggestions?

Or failing that, who do you northern Virginians use as a mechanic?