I have had my C230 for a little while now and for the last couple of weeks I have been hearing what sounds like pinging. Unfortunately I have had the car a short enough time that I can't say for sure that it hasn't been doing that the whole time. I use 92 octane all the time and the manual says to use 91 so that should be plenty good. Those of you familiar with pinging know that it can take on many forms. What I have is definitely not loud knocking. It is a light raspy sound that is definitely proportional to engine load but unlike other pinging I have experienced in other cars, it starts even at very low engine load. I suppose it could just be inherent in the engine but it really sounds like pinging to me. I will likely take it to the dealer for a test drive and get their opinion but I am interested to hear if anyone has had this experience with theirs or any input on this. If not pinging, is it just an exhaust noise? I have checked underneath the car and everything seems very tight and in good shape.

Thanks,
Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I have done some more "investigation" into this problem and also called the dealer. I determined that the noise is definitely engine load related. So that suggests pinging. On the other hand there are 2 reasons that I question pinging:

It starts even at very moderate load levels (slight hill) and also, at its worst doesn't really sound like any pinging I have ever heard. It seemed worse around 2500 to 3000 rpm, so I tried a test where I coasted at around 30mph and shifted into neutral and reved up to that range, nothing, no noise. So all I know is the tranny has to be in gear. Some times it almost sounds like a bad bearing. Very strange.

I called the dealer to see about making an appointment and talked to a senior tech there. After explaining all this and telling him I had been using 92 octane as the manuals says to do (actually says 91) he immediately said to try "high quality 87 octane". I had been using Arco 92 octane which has 10% ethanol (around here anyway). He claims that the name brand gas doesn't have the ethanol which surprised me since I though it was mandated by law. Anyway, he says this 87 octane idea for the 4 cylinder cars comes from high levels within Mercedes and is not just his idea. When I questioned this wisdom since it is a high compression engine he said it is not "really very high compression". Unfortunately I have a full tank of the 92 and don't drive huge miles so it will take me awhile to try the 87 octane. Does anyone have any opinion of all of this???

Thanks,

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I certainly think having a qualified tech look at it is wise.

And I have heard a way to tell if rods are knocking is to rev engine to 2K rpm in neutral and modulate the gas so the tach rocks back and forth by the 2000 rpm mark buy a few hundred rpm each way. Listen for the knock.

Listening to another C230 is a good idea.

I have a C230 and it is a engine with lots of little noises coming from the head. always has been and I run 0W40 Mobil 1 synthetic since available and synthetic from 1600 miles when new.

also with pinging from off timed combustion you'll notice it most under load when hitting a hill and the rpm are low - to high a gear on a hill.