drdan

My 2001 S600 has been running great, but suddenly has the CEL on with error codes of p0300, p0301, p0302, p0303. This shows misfire codes on cylinders one, two and three. No other misfire codes for other cylinders. Car will idle and run rough until ignition switched off and on again. Ran fine all day today and then acted up again. It would seem fuel pressure would affect all cylinders. It may be a possible ignition module for bank 1 cylinders, but that would probably affect cylinders 1 to 6. I'm thinking possibly a dying cat. There are 4 cats for 3 cylinders each, but wouldn't a bad cat trigger an error read from the pre and post cat O2 sensors? Car has 115,000 miles on it. Spark plugs and fuel filter replaced 15,000 miles ago. Any advice would be great.
Thanks

Ag E55

I had the exact same thing on my 01 S600. Ended up costing me over $5k and still doesn't run perfectly. First, go purchase a electrical contact cleaner and clean the MAF sensor. Pretty easy job, it should only take 15 minutes. If that doesn't work, most likely need a coil pack replacement. Take the engine cover(air filter housing) off and take a very good look at the ignition wires (the coil wires that run deep in the middle of the engine)..see if the wires are soaked with engine oil....mine was. There is a rubber plug that over time errodes and let's the oil leak in which the oil rides the wires up and ends up soaking the entire coils...sometimes, it will even destroy the ignition module. Since your misfire codes are only on the right bank, if you have to replace the coil pack, you should only have to replace just one, it will cost you about $1300 just for the part. but before you do this, clean your MAF and see what happens. My guess is that she will run just fine after you clean it.

good luck.

Quadcammer

a dirty maf would have to be REALLY dirty to cause misfires, and unless there's two of them (which I don't believe there is), it shouldn't cause a 1 bank misfire.

I'd say the ignition coil is the problem and is common. Parts.com has the part for $845.

drdan

Thanks for your advice. My Maf sensor was dirty before, which caused misfire codes, but also maf sensor codes as well. Replacing it fixed everything. I should have tried cleaning it to save $400.00. I think what I will try is pulling the ignition module for inspection. I know burn marks on the red rubber seals indicates a problem. I'll clean it off and reinstall new rubber seals. There is some oil from the valve cover on some of the metal tubes coming from the ignition module. The problem is intermittent, more after the car warms up and never when it is cold. Does anyone know when the O2 sensors should be replaced. There are 8 of them. Some cars have it as maintenance item at around 100,000 miles. There is no mention of it anywhere for this car. Is the ignition module from parts.com a genuine mercedes part? Thanks.

Quadcammer

yes, parts.com is an intermediary for MB of naperville. All parts are OEM, in an MB box, from an MB dealer.

good luck

ssonss1

Exact reason i traded the 01 S600 in...MISFIRES! after replacing all the plugs twice, MAF, both ignition modules, and a few other things that i can't thing of right now, it still misfired! although after the repairs it would run fine anywhere from a week to two months. It was an endless money pit.

My advice, sell it or trade it in, ONLY if you can't get it to run right.