Mikeyb

Friday, my '97 E420 (102,000 miles) immediately started running rough on the way to work. I checked the codes and had 5. No codes were present immediately before this.

Here are the codes: P0303 (twice - Cyl. 3 misfire), P0432 (Left TWC), P0455 (Evap System - large leak), and P0300 (random misfire).

This indicates a misfire at cylinder three.

Any ideas on what would cause all these codes to pop up?

Thanks for the help!

E-Class Owner

make sure all vacuum line are intact, a large vac leak can lean out the mixture, causing all sorts of problems. Secondly, and this is a common problem with E420's with high miles, I would suspect a bad coil pack. As an experiment, swap the coil pack in question with #2, or #4, clear the codes and see if me misfire moves.

I had one coil pack that was failing on my E420 [with quite a few less miles than yours...] which triggered a bunch of "sympathetic" error codes being thrown; I suspect that it was shorting internally and was back feeding to the ECU and giving the processor fits... The local dealer/"stealer" states that if they find two bad coil packs on an engine, they replace them all as a matter of course.

Let us know how you make out.

JR