'93 E36 Pining, pinging, pinging

[Rubatoguy]

Hello,

I have a '93 325i that was recently tuned and shows no error codes. However, on part to middle throttle, you can hear the engine ping constantly.

This is with premium grade gas, and when the car was tuned they did a fuel injection cleaning.

Does anyone have any suggestions as to what to look for?
I have already replaced an old vacuum line - no difference.

Thanks,
Todd

[Chilly]

Definitely stop driving it until corrected. Pinging sounds innocent enough but it's a devastatingly powerful pressure wave that causes temps to peak rapidly. Prolonged pinging may crack piston rings or burn holes in your piston or head.

Detonation and preignition are two different animals, though the symptoms may be similar. Both are an uncontrolled burn where the fuel/air mix isn't consumed in an expanding flame front. Rather, uneven pockets may self-combust (explode as opposed to a burn) due to high pressures, hot spots, uneven fuel/air mixing, lean mixtures, etc.

Did they do a decarb treatment as part of the fuel injection cleaning? Maybe the decarb treatment loosened up a big chunk of carbon but didn't clear it. The edge of the carbon chunk might be acting like a glow plug, initiating the burn before the spark event intends. If it's a chunk of carbon it's probably isolated to one cylinder. Not sure how one might diagnose which cylinder without doing something like disconnecting one fuel injector wire at a time, but I'm not sure what damage, if any, that might cause in turn. Better check with someone who knows fuel injection before playing that game.

Or maybe their fuel system cleaning flushed some crap into one of the injector nozzles, causing poor atomization and resultant crappy fuel/air mixing. Poor fuel/air mixing causes localized lean and rich areas and the lean areas will self-ignite when the pressure and heat are sufficient during the power stroke.

Or maybe they advanced the timing too far, starting the burn way too early, well before the piston centers over and can get out of the way of the expanding gasses (downstroke).

Summary: Take it back to the garage. I'd recommend they check timing, then remove and clean fuel injectors, then maybe repeat the decarb. If the problem persists pull the head and scrape the carbon off the piston domes and combustion chambers.


Chilly

[Wayne 962]

Strange that there are no codes being kicked back. It could be that one of your knock sensors is bad, but that should also trigger a code.

Are you sure it's pining? Maybe add some octane booster into the tank, just to check to see if it is. If it goes away, then yes, it's probably pinging. If not, it may be something else...

-Wayne

[theInstrucTOR]

Are you sure it's pining? Maybe add some octane booster into the tank, just to check to see if it is. If it goes away, then yes, it's probably pinging. If not, it may be something else...

pining for the fjords?

the VANOS unit on some M50TUs made a noise that sounded a lot like pinging. Its not harmful just annoying