Extended clatter on start, slight at 2400 rpm

[dammad]

My '99 996 has the usual initial clatter as the tappets fill up and has done for a couple of years (as long as I can remember). I've switch oil weights, but nothing helps. However, it was just a 1second thing and so ignore it these days.

In the last few months I noticed a new clatter at start. Sounds like a heavy clanking sound (about 0.5s between clanks) at start up. Give it some slight revs and it disappears. Let it sit in the garage and it will take 30-60 s for it to subside.

I'm also getting a slight 'tappet noise' around 2400 RPM when I back off during normal driving. Nothing loud, just slight noise that an ear in the car can hear if used to the normal smooth running.

I thinking that since the car has 110k miles that the oil channels may be starting to get a little gummed up (even though I use 91 Octane Chevon fuel only). Any other suggestions?

I need an oil change (has been done regular on 10k intervals), so was thinking about putting in one of those 'engine cleaning' products to help clean things up before the change. Any suggestions on if (1) this will harm it; (2) a good one to use.

Dammad.

[1999Porsche911]

My '99 996 has the usual initial clatter as the tappets fill up and has done for a couple of years (as long as I can remember). I've switch oil weights, but nothing helps. However, it was just a 1second thing and so ignore it these days.

In the last few months I noticed a new clatter at start. Sounds like a heavy clanking sound (about 0.5s between clanks) at start up. Give it some slight revs and it disappears. Let it sit in the garage and it will take 30-60 s for it to subside.

I'm also getting a slight 'tappet noise' around 2400 RPM when I back off during normal driving. Nothing loud, just slight noise that an ear in the car can hear if used to the normal smooth running.

I thinking that since the car has 110k miles that the oil channels may be starting to get a little gummed up (even though I use 91 Octane Chevon fuel only). Any other suggestions?

I need an oil change (has been done regular on 10k intervals), so was thinking about putting in one of those 'engine cleaning' products to help clean things up before the change. Any suggestions on if (1) this will harm it; (2) a good one to use.

Dammad.

Check for loose parts first. broken guts of a cat, loose muffler/bracket/tailpipe/heat shield, back license plate frame, etc.