Hello All,

Does anyone out there have any ideas what could cause an 87 300e with m103 to ping when you lay into the throttle? I'm using 93 octane gas (91 is required). I installed the following tune-up parts about 1 year ago: Bosch distributor rotor, Bosch cap, Bosch dust cover, Bosch wire set, and the correct H9DCO non-resistor spark plugs (torqued to the correct 15 ft-lbs), and all of it was ordered from Mercedes using my VIN, so I know it is all correct. Also an air filter from Meyle of Germany. It was pinging before I did the tune-up as well. Could it be that the coil or crank sensor is getting worn out, or maybe the pistons have too much carbon built up?

Any ideas are greatly appreciated!!

Pinging is usually from either too low octane of fuel, which it sounds like you eliminated, or overadvanced ignition.

i would say overadvanced ignition for some reason.

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1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes

You forgot oil contamination. The valve guides in the 103 engine are notorious for wearing excessively allowing oil into the combustion chamber, causing pinging. Pull the plugs and inspect for oil fouling. If it's bad enough that the spark plug insulators are cracking or missing then you really need to do a head job asap.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

Second that opinion: fouled spark plugs seems like the most likely cause of pre-ignition. A high mileage (150,000 +/-) 1987 300E probably needs valve guide replacement.

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Fred Hoelzle

Try changing the oil and using some Bahr's Stop Leak, and 10W40 grade oil (I used Pennzoil) and all my noises...pinging, and header noise went away. Also used a Bosch filter. Auzone has a deal right now if you buy 5 quarts or more of Pennzoil you get a free Bosch filter. With the Bahr's, cost me $40.00. Worth a try and you need to change oil anyway.

A lean condition can also cause pinging. If timing checks good, check fuel pressure.

Thanks for the replies guys!

I had the head redone about 50,000 miles ago w/new valve seals, guides and a remachine. I looked at the spark plugs about a week ago and they were in great shape. Take this into consideration: I have a slow oil leak from the head gasket to the outside of the block (not into coolant as is typical). Possible head bolt torque issue? Or maybe bad gasket

Yes leak could be from those issues but the pinging could have been miss aligned timing marks.

M103 timing is electronic and determined by the EZL and a resistor - R16.
Unless this resistor is missing I would be looking at the CPS or coil as well.

Thank you all for the replies. Can anyone tell me where this R16 resistor is located so i can make sure it is there and in good condition?