Pinging at idle after long drive
 

I had a new set of tires put on and "balanced"

then I left town and drove 200km, once I got up to 60mph I would start to get a pretty bad "wobble" or "shake" in my steering wheel. so I think "great" the idiots did a bad job at balancing the new tires. so I did my best to keep under 60 and stay away from the wobble to much.

once I got in to town last night, I noticed the idle sounded kind of strange. Pingy I guess, sounds a bit like a diesel. I started it up this morning and it has the same sound.
I was reading that pinging tends to happen under load? but this happens to me at idle. I am going to go fill up with the highest octane fuel I can find and see if that helps.

Did you buy all four tires? I had a similar problem when I only replaced the rears.
I would get up to about 60 and it would feel all wobbly and randomly wandering right and left.
Turns out that my front tires had a wear pattern that was not matching with the new rears. I replaced the fronts and the problem went away.

Need background info.
When was the last tune up. Have you checked your ignition timing, distributor advance weights, vacuuem unit, cap and rotor, made sure your spark plugs and wires are in good shape. Check for vacuuem leak at intake manifold. Fuel filter.

You won't hear pinging at the idle - its something that worsens with load.

If you hear a metallic noise at the idle, need to hunt it down, as it could be something in the tensions/chains or the fan making contact. Use the 'broomstick' method to try and track it down.

Put a broomstick parallel to your head, pressed against your hear. Use the end of the stick to touch different areas of your engine (obviously not anything moving like the fan). Fan housing - yes, fan itself - bad idea. :D Anyway, this amplifies the sound and lets you hear where it is coming from. The price is right on this diagnostic system.

angela

i had a rocker arm shaft that came lose and made a lot of noise, although that might be kinda rare.
could be piston slap. usually gets worse with synthetic oil.

broken valve spring. you would need to pull all the valve covers and check the springs.

valve guide making noise.

i dont know if a broken piston ring would make noise or not. perhaps a leak down test and/or compression test.

broken head stud. can be checked with valve covers off.

exhaust leak. get under that car and listen with it running.

rod k nocking. gets worse with RPM increase.

just some stuff to scare you. hope it turns out to be nothing.

I'm not sure what flavour of 911 you have but I'm assuming since you are suggesting going out to find the highest octane fuel you can find, that you're not doing that already. I always fill my car with the highest octane fuel I can find and still I have to occasionally run Techron through her when she develops a slight miss at low RPM. Driving under 60 mph in fifth gear, burning mid grade or lower for 200 kms might "carbon up" my car. I doubt it would sound "pingy" at idle, but it's possible since my car already has a higher compression ratio than most 911's. Pinging can be caused by carbon deposits partially igniting the fuel/air before the spark occurs but as was said in an earlier post, it normally shows itself under load and not at idle. Cheers BTW in the lower mainland Chevron 94 in the local choice for most 911's, no ethanol....good stuff.