Hello everyone, this is a tread I originally posted on FB and 911uk.com and I wanted to forward it there because i'm trying to gather as much answers about this as I can :

I'm worried about a knocking noise coming from my engine and wanted to ask if anybody already experienced this, since I got the car a year ago it has always been there and I can't find anything about it online...
Someone told me it could be bad valves timing, another told me it could be the throttle body.

Also this only happens when the car is idling (900 rpm)

Here is a video of my engine bay while the sound occurs


997.2 C2S early 2008 build



After a scope inspection, the noise really seems to be the loudest @throttle body, one of my mech friends told me it was totally normal
Peeps from 911uk told me it could be related to the belt tensioners, i'll bring again the car to my friend tomorrow and we'll remove the rear bumper in order to check tensioners.
Any people here already experienced such noise on their .2 ?

 

Strange. It doesn't sound rhythmic, making me discount the idea of internal engine issue. Perhaps those with more insight can provide better suggestions

 

A mechanic's stethoscope is inexpensive and may help you narrow it down. Good luck.

 

That's what I meant when I said scope inspection

 

Sounds like a misfire to me. Hook it up to a Durametric, enable misfires for all cylinders and it will show you which one is misfiring. When we're spark plugs and coil packs last replaced. That's usually the cause of misfires.

 

Agree with pete. Or could be a super early/late ignition? Starting with the intake is still open?

I dunno. But I'd start with the easy, usual suspects first.

Cw

 

That's when it gets tricky, as mentionned, as far as I remember I always heard that sound from the engine since I got the car a year ago BUT, my hpfp failed before the COVID lockdown (on Febuary 18th to be exact) and I just got it replaced like 2 weeks ago, and when serviced I also asked my local Porsche Center to replace coils and spark plugs, so I can't imagine it's coming from these

 

OK, but first let's see what's causing the noise. Since it sounds like misfiring, let's track those and see if you're logging any. Which cylinders will give us a direction, like if it's a single cylinder, a bank of cylinders, or more random than that, or maybe it's not a misfire at all and we need to look elsewhere.

 

sbbarnett has it right..... Get a stethescope..... you can hear if it is coming from a cylinder or wherever. Harbor Freight has them for $5.00.
BTW.... misfires usually throw a dash light in my limited experience.

https://www.harborfreight.com/Mechan...ope-63691.html

Peace
Bruce in Philly

Video of me checking out my pumps.... again, a whole $5.00 worth of effort.

 

Update : the car will be inspected @local OPC in a week

Also, while doing researches on 9A1 engine I found a thread from user Pho King Fast who posted a video with the exact same noise, take a listen :


Turns out it was the throttle body as he said in the last reply of his thread : https://rennlist.com/forums/997-foru...ports-aos.html


@@Pho King Fast, what was the fix for this ? Did you replace the TB ?

 

Yes I had the same tin can metallic noise on my 2010 C4S some years back. It is the throttle body flap in there rattling. The plastic bushings or gear mechanism wears out. You probably have an unsteady idle as well. I'd just replace the throttle body yourself and save the shop fees.

 

That's exactly the noise I had. exactly.
Replacement / Clean Throttle Body And in addition, equally important, check and replace the plastic breather pipes that connect to the throttle body.
They tend to crack over the years, which causes the throttle's butterfly to become confused and also cause unstable noises and combing.
Successfully

 

Update : successfully replaced the TB myself and the noise is gone, also rock steady idle and the car is more responsive !

 

A success story! Glad to hear you figured it out and solved it yourself.

 

That's what it sounds like...