Trav63

Hi all, sorry to post this thread, i know there has been a few of these in regards to pinging. I have a w204 C63 with 140,000km and have tried many recommended maintenance items to stop the pinging. It only happens under light ish throttle, any gear, any driving mode, no codes, car is not tuned. I have changed plugs and re checked the gaps, new MAP sensor, cleaned MAF sensors, only use BP ultimate or Caltex Vortex, both 98 RON, tried liqui moly fuel treatment as well. 1 other symptom, at idle in P, the engine does hunt in revs a little but this is inconsistent and can range between 800 to 1100rpm's. Both issues only appear at full operating temp. Any advice/suggestions for this newbie would be greatly appreciated.

Solo wing

The specified values for idle speed in SDS are [632-732] RPM.
[800 - 1100] RPM does seem to be higher than normal. Could this indicate a vacuum leak, since it occurs only at operating temperature?

BalanBro

Check your long and short term fuel trims at idle and light load. That should give you some insight as to what's going on.

Trav63

Yes, thanks for confirming the target range. I Will get started on checking for a vacuum leak.

Trav63

Thanks man, what numbers indicate an issue vs whats normal? I seem to recall seeing a number of .69 but I could be very mistaken and will check it out again on the scanner.

BalanBro

LTFT and STFT are in percentages. If you're completely stock, they should be +/- 5% on both banks. If you're seeing more than 10%, either you have some modifications (airboxes or a tune) or something is wrong, like a vacuum leak or bad sensor.

Trav63

Thankyou, I took 2 videos, 1 at idle which never went outside the range you mentioned, under light load however it was a different story

@1500rpm

BalanBro

While those number aren't terrible, the negative trims mean the car thinks it's running rich and pulling fuel to lean it out. Have the O2 sensors been replaced? I'm not suggesting to throw parts at the problem, but that's the next area I'd look to diagnose. O2 sensors will start to take control of the fuel trims once they are warm.

Trav63

I have not replaced o2 sensors, no records of it ever being done. I dont think the last owner was as particular on maintenance as me, it has full service history at MB but I want to make sure everything is mint, especially considering the age and km's travelled. I could not be 100% certain that there is not a tune either, it had some cheap AF carbon fibre intake tubing and front dam from alixpress but I have sourced the originals now, standard air boxes were there, the issue was there prior to me changing back to stock . Funny you mentioned the sensors as I got sent a blog from FCP the other day and it was talking about o2 sensors. I think I will change them out anyway to be safe and at least they are done, maybe it will fix it.

Trav63

Thought I would just update this thread for anyones future reference, thankyou for everyones suggestions, I replaced the upstream O2 sensors, no more pinging and idle is sitting around 850 rpm consistently. Thanks again.

hachiroku

idle should be 580 to 650rpm...no higher. i'd continue looking for other issues if that high of an rpm bothers you.

Mahoo2

silly question, what is pinging? My C63 is what i call surging under light acceleration throughout the gears when hot. Does this sound the same?

hachiroku

pinging refers to pre-ignition or detonation within the engine which causes damage.

pauliepaulie123

Hi there, I have the same motor and same kms and same issue. I just wanted to confirm, is that pre cat or post cat O2 sensors. Not sure if your able to reply but it would be most appreciated. Cheers Paul

Solo wing

Downstream sensors have no effect on the mixture. Only upstream sensors do.

BalanBro

Pre cat sensors, but check your fuel trims first to make an educated diagnosis. Throwing parts at a problem gets expensive quick, especially with an AMG.

hachiroku

surging shouldn't be occurring with a factory tune or any good tune. if you have a shelf tune, the surging is due to the tune.