Knocks knock

[Belgian951]

Hearing something like knocking after standing still for another few months.

My thinking is:
- old gas with too little (and too late) added stabilizer is bad
- vacuum leak (hear hiss)

Results in the knock.

Is that thinking correct or would these two factors not contribute to a knock?

[gb951]

Do a smoke test and fix your boost/vacuum leak.

Then, see if you still have a knock.

[NC944er]

I would probe around with a mechanic's stethoscope and see if you can pinpoint the noise.

Start with the camshaft assembly. The hydraulic lifters can get a little clacky when the engine hasn't been run in awhile.

Checking the level and condition of the engine oil is also a good idea, if you haven't done so already.

[Tom]

Post a video (via youtube, etc.) so we can hear it...