I have a 84 944 with an unkown amount of miles on (odometer has not worked for years). Although a new top end was put in around 8 years ago.

I have a knock that seems to be coming from the top end but the funny thing is it only comes in at around 1300-1500 rpm. At idle nothing and as soon as the rpms increase it goes away. It sounds quite loud for that moment. I checked the oil and as far as I could see there were no metal shavings in it.

Could this be just a bad lifter or something more serious.

Thanks for any help

 

there is a fuel cutout around 1300 RPM that lets the engine get back to idle, this is what causes the stumble when you let off the gas...this might be the cause of the problem.

i remember in the porsche owners manual it said to always downshift if revs drop to 1500 or below, maybe theres some hidden reason why?

 

Well maybe thats it.

Engine runs great otherwise and I have good oil pressure.

 

Does it happen when the engine is cold and hot?

What weight oil is in it?

 

happens every time

I have 20w 50 in it.

It goes away as soon as you go over 1500 rpm and it is not there at idle at all

 

I actually had something simular as you.
It turned out to be my a/c compressor rattling around.
One of the mounting bolts had sheared off, and the compressor was loose.
At certain rpms it would make a knocking sound.

 

dude....are you serious? (the hidden reason why is because if your in gear when the fuel cuts the car will buck...its very uncomfortable and makes it look like you don't know how to drive.)

disregard the above statement OP

( i have no idea what it could be but /\ /\ /\ that guys idea that something could be loose sounds highly feasible. maybe stick your head in your engine bay [not too far!] and rev it up and see if you can't pinpoint it further)

 

now that I think back we used to have an early style car and it was doing the same thing. I think it was a heat shield hitting the exhaust. which goes back to just check everything in the engine bay and under the car.

 

Yeah it does seem like something is loose in there somehwere

Thanks for the help

 

DO NOT store empty beer bottles in the engine compartment for this very reason.

really. You do have something loose in there. That's all. When I have rattling sound problems, I do either 1.) drive next to a long building listening for where it's coming from or 2.) stand next to the road and have someone drive by in both directions.

A lot of times the sound isn't actually coming from where you think it is.