2.7 knocking at low RPM?

[Soarer20]

At around 1,100 rpm (when warm) there is an noticeable knock. Oil pressure gauge is reading below 20 at idle when engine is warm.

Could this be caused by a low oil level?

With a dry sump system is it possible for a low oil condition to cause this?

I have yet to do more diagnostics to try to isolate it to a particular jug. John Walker mentioned the left side tensioner/ chain was noisy...

[jason2guy]

by knock, do you mean detonation? if so oil level probably isnt a contributing factor. could be a lean mixture, timing out of spec.
if you dont mean detonation, that could be serious

[DRACO A5OG]

Video it and post.

+1, Lean Mixture or Timing issue.

Sounds are subjective so a video could help clear your potential issue.

[Soarer20]

You can clearly hear the knock at :34 and again at 1:30.

https://youtu.be/qPYmhKjM_i8

[Trackrash]

It sounds to me like one cylinder is limping or missing. Fouled plug?

I don't hear any "knocking" per se. There is a valve ticking, but nothing bad.

What do the plugs look like?

You should get a stethoscope and see if you can isolate the source.

[gomezoneill]

Sounds like a wrist pin knock to me.

[T77911S]

yea I heard what you are talking about.
the valves are a higher pitched sound, the other sound is a low pitched knock. I have heard it on other cars but don't know what it would be,

I would go thru the valves, check the lobes, check the head studs.
go ahead a doa compression check just to see where it is.
then take another listen.

[RSTarga]

You have no oil pressure. The needle doesn't even move when you rev it.

[ischmitz]

You're in John Walker's area. Maybe stop by his shop and get an expert opinion?

[RSTarga]

Tow it to the shop

[Soarer20]

Originally Posted by RSTarga

You have no oil pressure. The needle doesn't even move when you rev it.

True. I think the oil pressure sender needs replacing. I didn't want to pull the motor to do it.

The knock doesn't sound like a rod bearing. I'll ask Walker.

Jeff H did the motor not that long ago. Walker did a valve ajust not more than 300 miles ago......................

This car has been bad luck the whole time I have owned it. Someone make me an offer. seriously, I want a 964!

[analogmike]

I am having the same issue on my freshly rebuilt (about 3 races old) 2.7RS engine.

At low idle, it will occasionally knock pretty loudly with the oil pressure dropping.
No noises at higher RPMS. Speedsport tuning got it running well but could not find the problem without opening the engine.

I have a big vintage race at Lime Rock in under two weeks, afraid of running it like this.

Did you find out what your problem was?

[Trackrash]

I had a similar issue. I would recommend using a stethoscope to isolate the noise.

You may want to post a video with good sound. Maybe someone would have an idea of the source.

Here is my thread. Knocking noise in motor?

[Locker537]

Gordon, did you resolve your issue? Ignore it?

These threads make me wonder if I'm hearing things on my car after!

[Trackrash]

It is coming from the right side chain idler on my motor. When I opened up the chain cover I could make what sounded like the knocking noise by moving the idler pulley back and forth on the shaft. Seemed to be quite a bit of side play. It isn't doing it as much any more and isn't noticeable when warmed up. I have over 6K miles on the motor. My guess is the idler pulley is just rattling back and forth at a certain RPM.

Listen to the video I posted and compare my sound to yours.

[HaroldMHedge]

Mike,
I would install a mechanical gauge to confirm the oil pressure. You may want to install the later cam oil line restrictors. This should increase your idle pressure.

[proporsche]

Mike ;;make a video ..it will help us to locate your sound better
Ivan

[analogmike]

Originally Posted by proporsche

Mike ;;make a video ..it will help us to locate your sound better
Ivan

It's a loud slow mechanical knock, I thought it was from the chain housing but I ran it with the cover off and all fine in there. I can't confirm the pressure issue (SST mentioned it and they used a VERY expensive accurate mechanical guage).
The knock occurs more frequently when the engine warms up and the idle goes down. Runs perfect at fast idle or up to redline.

Here are some videos:



https://www.youtube.com/watch?v=hGRFJu6Ad40

https://www.youtube.com/watch?v=hiF2EEQxYRU

I wish it were easier to access the clutch and flywheel, that's another possibility.

[dannobee]

Flywheel is loose.

It's not a rhythmic knock like something internal.

[analogmike]

Could be flywheel, I will listen carefully in that area tomorrow and pull the trans if I think that might be it. thanks!