Engine Pinging

Can you describe the sound a little better? Or maybe post a video?

How recently has a tune-up been performed? Maybe a simple fix will correct the problem.

F. Jason Garriott said:

It's high mileage, at 150.000

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Almost certainly carbon build up inside the combustion chambers.
There should be an additive you could put in your gas tank to help clean some of it.

Car stock? My 06 is stock (Well Axlebacks, but they don't affect anything but sound) and has 160,000 miles, no pinging on 87 10%. When the plugs would get old, I would get light pinging though. I could run hard through the gears a few times in a row, and it would clear for a while. Once, cash was tight and I had already switched to the one piece Champion 7989 plugs. I pulled them, gap was WIDE. Cleaned them, closed the to Champions suggested gap of 45 instead of factory 55 (I think those numbers are right, but I know Champion likes the tight gap regardless). Car runs perfect with those now. I'm about to replace them, cause they have 100,000 miles on them though. Seems like I had around 60,000 when I regapped. And 60 when I replaced the stock plugs.

So... you have about 50,000 on your plugs. The gap may have worn open and out of spec. I'd run some good cleaner at double strength for a whole tank, then change plugs. I say run cleaner first to clear carbon from plug shaft (Which can also heat and ping) so you don't break them in the head. Still use Carb Cleaner in the top and let soak after a VERY SHORT cracking the plug loose.

Keep us posted!

When changing plugs or doing a tune up, I like to run the engine just long enough to suck a can of Seafoam in through the brake booster hose, let it sit or about 30 minutes, and then drive it like I stole it. Copious amounts of smoke is normal.

F. Jason Garriott said:

Hi all:
I've an '05 GT, 5 speed, runs great in the worst LA traffic in the world. It's high mileage, at 150.000, it pings lightly under light to hard acceleration. I'm running 89 octane, up from the 87 stock spec. Is it valve/piston top gunk? Tuning? Should I run 91?
I can't tolerate pinging, even at a small scale.

Please Advise.
Thanks, all,
Jason.

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Try running a full tank of the higher octane (91). If that helps and you have a fresh tune up then you might be due for a seafoam treatment to clear deposits on the valves and pistons. I'm not a big fan of seafoam, but it might help.