Date registered: Oct 2005
Vehicle: 1955 300SL, 1999 SL600, 2011 C55 AMG, 1980 450SLC
Location: America the Beautiful
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Usually if your wires have a bad one or more it doesn't change characteristics when it warms up, it might misfire a little more at higher RPM though. Possible vacuum leak? If the problem only recently started, possibly check that the plugs are the ones that esteemed forum member Jayare recommends, and that the gap is correct. You don't want resistor plugs because these cars wires have resistor built into the end of the wires that connects to the spark plug. They say that platinum plugs have a lower intensity spark, however I used them with no bad result. I have since changed my M104 to a Bosch F8DC4 as per Jayare's recommendation and all is well. Many years ago, I changed plugs on a car then shortly after that, it quit running altogether and we spent countless hours and days looking for the problem, can't remember why but it finally was learned that the plugs were the problem! To check the plug wires, use a volt meter and check the resistance of each wire, they should all be very close in terms of resistance. If one or more are very different than the others...voila. Also look closely at the connections at each end making sure there is no corrosion or damage. I always use white silicone grease on the spark plug end to make sure the wire will remove easily without breakage next time, and I always use anti-seize lubricant grease on the spark plug threads. My 1990 M104 has distributor cap, rotor, and single ignition coil which I replaced with a 60,000 Volt Jacobs Electronics Ultra Coil which gives a very powerful spark. But that's just me. Be very gentle and careful when removing the wires (one at a time so you don't get them reinstalled incorrectly) remember that they are expensive and if they are indeed in good order you don't want to break one of them and then have to replace...Good Luck,
Please don't spill Champagne in the Mercedes.
Last edited by tonylinc; 05-23-2010 at 01:55 PM.