Butler05

Here's the facts :2005 C230k Sedan w/ 71k. CEL light came on drove to Autozone and receive codes P0301 (misfire #1) and P0128 (Coolant thermostat). Thought the P0128 code was strange as I replaced T-Stat last year, so I followed advice here and replaced spark plugs, T-Stat and #1 coil. Drove car no light warms up just as normal can drive car up to 60 mph with no issue as soon as the rpm's and car goes above 65mph the misfire occurs and CEL light come on with same codes 128 & 301 (this happen right after installing the new parts). As soon as I pull to side of road I shut of car and quickly restart, it acts as if nothing happened and all is well. Any Ideas? Thanks

By the way car is well maintained no cam leeks or other issues, first issue in 4 years of ownership.

sammydragon3

is their oil in the cylinder walls? from a worn valve cover gasket
i'd perform a compression test on all cylinders ...should be around 160

i hope ur engine isnt ****ed up i got the same car lol

Butler05

Engine is clean, no leaks period, cam magnets are dry including electrical connection. Don't have tool for engine compression, maybe a trip to dealer, ouch that hurts typing that.

sammydragon3

i wouldnt agree on going to the dealership .


mercedes has a bad reputation for being expensive to fix and maintain due to the fact the dealership will cost u 50% more than any other shop to do the same job

almost to all mercedes dealerships in america arent even owned by mercedes back in deutschland

Glyn M Ruck

This is a most unusual combo & you will probably have to untimately get the car onto a Star diagnostic machine. The way they clear after a reboot is a worry.

The only things that can cause a false P0128 is the temperature sensor or ECU itself.

If plug & coil are not causing the misfire then we are left with a fuel problem to that cylinder so the injector becomes suspect. Run a couple of tanks of fuel with Techron concentrate in case the injector is dirty. Check fuel pressure. When last did this car have a fuel filter?

Check plug on the main harness to the ECU for corrosion - you say you don't have the dreaded oil in the harness. Pray you don't have an ECU problem.

Good luck!

3chordpete

I had the same DTC's plus a couple more. After a little research I found an M-B fixit campaign that was not widely known.

Check with your M-B dealer (mine is Keyes European in Van Nuys, CA). The campaign has to do with oil fouling a wiring harness located near the transmission. M-B replaced the Mass Airflow Sensor, both O2 sensors, and a couple of other components at their cost. And the DTC's were gone.

I have a W203.040 with the M271 motor. About 70K miles and this was not a warranty fix.

If you qualify the campaign will save you many $$$ and headaches.

Good Luck!