I have a pinging sound in my car coming from the rear of the engine or transmission area. It sounds like classic engine pinging, with a very metallic tinny sound. I've had this issue for at least three years and its getting worse. Many techs suggest fuel system cleaners etc, and of course I've run em all through the car without any improvement. I also only use premium Shell or Chevron gas. The pinging sound only occurs during coasting, NEVER during any throttle input. It's the worst when my foot is barely touching the gas pedal; not enough to keep the car at a constant speed, but also not a full coast. Does not occur at idle with the car stopped, even if I rev the engine. I've replaced the exhaust y-pipe, and done several thorough checks of the car. All maintenance as scheduled. I do have the original MAF in the car and it has 157,000 miles. Could a bad MAF cause this? Ideas? Anyone ever had a strange unexpected failures of parts that usually don't break or go bad?

 

Does the "pinging" sound change at all when hot, cold? Could be a clue there.
Also, does it occur only while in gear (albeit a near coasting) or would a high idle in neutral/park also do it?

 

It is possible that it is some of the heat shield sheet metal? It sounds like you have checked about everything else.

 

No difference when hot or cold. I can only detect the noise while driving. In park no matter how I rev the motor it will not make the noise; high revs, low revs, stabbing the throttle, gradually increasing the revs.... nothing causes the noise in park. I've even had the car running on a dyno with me under it with a stethoscope and and I could not hear the noise, but the dyno would mimic a load condition equivalent to the car being under throttle so it didn't surprise me that I couldn't hear anything.

A loose heat shield is what you would think it is if you heard it, but I've removed the heat shields on the y-pipe and I checked the remaining shields on the exhaust manifolds and elsewhere.

 

If you're not getting a code, I wouldn't worry about it. Try an octane booster not a cleaner, but I doubt it will make much of a difference.

 

I found this video that is showing exactly the same noise I have, albeit to a greater degree. The noise in this video mostly occurs when the revs of the engine are coming down, much like mine, although this car's rattle is audible in park too. I think a loose core inside one of the cats is likely the problem; I've gone through every system on the car and it's the most likely candidate. I am not throwing any related codes though, which I surmise could be the case if the core is only just loose within the casing.

 

With your description of symptoms, I am really thinking maybe the torque converter or flex plate. You might try to determine if the torque convertor is coming out of lock-up when this noise occurs or if there is a speed at which the noise is most noticeable.

 

Wouldn't the car present with transmission and shifting issues if the torque converter was going bad? Also wouldn't a torque converter problem escalate into a huge failure of some sort sooner than 3 years/50k miles? It used to be most noticeable on the highway, now it's any speed.

 

Yes, I suppose you are right in that reasoning. You might broaden your hunt to include checking wheel bearings, mounts, suspension parts. I know it does not appear to be coming from those but noises can be tricky to identify and sometimes come from unexpected sources.

 

I've replaced all the engine mounts and ALL the suspension parts, including the upper control arms, steering rack bushings, and inner and outer tie rods. The only time the noise changed was after replacing the two broken front engine mounts, the noise mostly disappeared for a few weeks but then came back. If it is indeed a loose core in the cat, I suppose changing the engine mounts would impart a slight flex to the exhaust system, which could cause the loose core to not be as loose and not make as much noise, but then slowly loosen up again.

 

If it were a loose core in one of the cats, could you use a mechanics stethoscope and pound on the cat (while cold and not running) to listen for a rattling noise? That might reveal something especially if you got a different noise out of one of the cats.

 

Have you serviced your transmission and differential? You are probably hearing gear whine not pinging. Could also be a bearing starting to go out.

 

Yes both have been serviced.

 

Your car will be almost brand new by the time you fix the pinging.

 

Haha I keep thinking the same thing after every repair. Still waiting for the new car feel though LOL. As soon as I fix one thing, something else breaks. Got two nice rips in the driver's seat pad recently...