Redblurr

I recently have been hearing a knocking sound from my engine. The noise only occurs when I hit right around 3000-35000 rpm. I only hear the sound between those rpm's. It does not sound good, so I have only driven it twice since first hearing it. I dont have a P-car mech nearby or I would have taken it to a shop, but I am reluctant to drive a great distance. Any Ideas or thought would be greatly appreciated. TIA. By the way, its a 1995 993 with 120k on the clock.

Quadcammer

whats your oil pressure doing?

abiazis

First option:Tow it to dealer or shop or

2: drive it under 3k rpm to nearest P-car shop...

Let's us know what it is....for future reference.....

Stealth 993

Can you do a little video of the sound? Have you made sure you don't have a loose exhaust or headers? Broken engine mount, or carrier? Evan a flywheel can make racket when it's about to fail.

The sound might not be the engine, but the engine is making it resonate around 3000rpm's.

Redblurr

Oil pressure is normal, at least the gauge says so. I can make video clip of sound but not till tomorrow because I'm working and car is at home.

Davies

When were your plug wires/caps rotors etc. last changed? Arcing wires'll ping up your engine nicely.

Glen Watkins

I had a similar situation happen on my 95 993 when the secondary dist. belt broke and caused arcing between caps. -You can test this by removing one coil wire at a time and trying to start the car. If the car fails to start with one of the coils disconnected, follow that wire to the cap and inspect. -Mine had a small hole melted through it where the ark was occurring. -You may also try removing that cap to see if the rotor is turning while you crank the engine (don't forget to pull the DME relay when trying this!) Good Luck!

Stealth 993

Super easy check, start the car in the dark, get a spray bottle with water, & spray it around the engine, look for sparks, & idle change.

Garth S

A similar deal recently caused a racket 'from' my engine .... the ducting from the top of the fan shroud to the electric fan on the left side had shifted slightly: this caused a loud resonance noise, much like a knock ..... and was cured by loosening and shifting the support brackets a mm or two.

Hope yours is a simple cure ....

Quadcammer

look, if this was a bearing issue, you'd most likely hear it through the rev range.

Given that this occurs just between a small rev band, I'd imagine it could be a resonance issue causing something to vibrate.

Loose muffler maybe?

Redblurr

So I took a video. The knocking noise isn't real loud but I think you can hear it OK. My distributor caps and rotors along with the drive belt were replaced 25K ago. What do ya think? (hope the link works)

Redblurr

Link works! Just click the pic.

Mike J

I listened...and it was really hard to tell, sounds like a 993. It might be easier if the throttle was held steady.

Perhaps someone else has better ears?

mongrelcat

I agree w/ Mike. Maybe more revs in the ranges where it doesn't 'knock', like from idle up through 4k, and then back down to idle so the distinction can be more easily heard. Hold the camera (mic) closer to the left bank as well.

Would an issue with a lifter be limited to certain rev ranges?

Quadcammer

I hear nothing