low engine rpm knocking?

[trevor144]

I have a 325e it runs fine it just makes a knocking noise from right about 1k rpm's and goes away by 2. This happens in neutral, while not moving also, so i know its not part of the drive train or anything. Could the valve's just need to be adjusted? It's more of a thud than a tick. No smoke, leaks a little oil. Somebody please help, I dunno if it's good to be driving the car like this...

[BMC227]

could be a bottom end knock, you can't really tell without hearing it.

[trevor144]

Dang. I just don't understand why the noise would only be apparent from right about 1k to just below 2k rpms..

[Blackangusinc]

It could be a sympathetic vibration from a loose accessory or bracket somewhere. That would make sense given your symptoms. Pop the hood, lean over the engine and open the throttle until you hear the knock. The source should become obvious.

Rod knock is usually always audible. It just gets louder the higher you rev.

[TurboJake]

I need to do this with my car. I get what sounds like a rod knock ever time I turn it off. But never anytime else. that little time between 600-0 rpm I hear about 5, maybe 6 knocks.
And I've never heard of "Sympathetic vibration" being used in place of resonant frequency. But I kind of like it. Dunno why, just do.

[trevor144]

What you are talking about is pre ignition -

http://en.wikipedia.org/wiki/Engine_knocking#Pre-ignition

[Blackangusinc]

I really doubt it.

[trevor144]

Damn that was directed to the dude who posted above me, not you. forgot to quote

[TurboJake]

Me?
IF me, It doesn't diesel. It just makes it as the noise as the rotating assembly comes to a stop. If I could place it accurately (Which I can't), I would say between the 200-0 rpm. Never right when I shut if off. But that second half of the 3/4 of a second it takes to go from idle to 0.

Honestly, now that I think about it. It very well could be my exhaust tapping the body of the car. It's REALLY close to the framerail. It didn't do it when it was an auto, but it has been a manual for 8 months, so my motor mounts are probably on their last legs.

[tim88325is]

Does the sound go away when you push in the clutch? Sometimes it is a input/throwout bearing issue which isn't too critical.

[SynSyx]

flywheels like to make noise, and you usually hear it when sitting at stop lights in neutral... if it goes away when you push in the clutch, theres your answer

[trevor144]

No my problem has nothing to do with the clutch, it makes the noise in neutral as well as under load.

[FLYNAVY]

No my problem has nothing to do with the clutch, it makes the noise in neutral as well as under load.

My UUC clutch rattles a good amount at times while at idle in neutral. If I remain in neutral and push in the clutch, it goes away. I think this is what the others meant, but I'm guessing that you would have noticed this by now if it were the case with your car.

[Jaxx_]

piston slap? is it worse when the motor is cold?

[dreamer420]

Me?
IF me, It doesn't diesel. It just makes it as the noise as the rotating assembly comes to a stop. If I could place it accurately (Which I can't), I would say between the 200-0 rpm. Never right when I shut if off. But that second half of the 3/4 of a second it takes to go from idle to 0.

Honestly, now that I think about it. It very well could be my exhaust tapping the body of the car. It's REALLY close to the framerail. It didn't do it when it was an auto, but it has been a manual for 8 months, so my motor mounts are probably on their last legs.

my Eta has done EXACTLY what you are describing ever since i made it a manual. my motor mounts are totally shot now too...