Own a car with the M103 Engine-Must Read!!!

[Gilles Kay]

If you own a car with the M103 engine, this information is very important. I'm not sure if this information has been shared here before, but it bears repeating.
I own a '92 300E which has recently been experiencing a longer-than-normal crank time both in the morning and after initial warmup. Engine idle has also been rough at times with an occasional miss. The problem was getting worse with time. I had installed the recommended Bosch spark plugs about 10,000 miles ago. I was browsing another MBZ forum and read a thread stating that Bosch no longer makes the correct, non-resistor plug for this engine. Using the Bosch plug or any other resistor plug can cause problems with the ignition system. The spark plugs wires themselves contain a resistance already built into the spark plug boot. The two types of non-resistor, pure copper spark plugs recommended were the Denso T20EP-U and NGK BP5EPS. I purchased the Denso plugs and installed them. WOW-What a difference!!!! Instant engine startup, smoother engine idle, and no occasional miss. My engine was truly transformed. If you own a car with this engine, you should definitely check to see what kind of spark plug you are running. No platinum or anything alse. Just a straight, non-resistor, pure copper plug. It worked wonders for my car!!!