My God, the SLK owner has had exactly the same problem as I have for e few months now !!!! (thread Plugs-SLK200 (R170)
My CLK has been converted on Liquid Propan Gas, that is, I can run it on Gas but also on petrol. I will not describe the symptons again, they are the EXACTLY the same as above, running ok for a few days and then degrading again included !! When it misfires with me it sometimes bangs in the exhaust system. Additional facts are: 1) Misfires when running on LPG and petrol. 2) Can't be the HFM, because HFM is not functional when running on LPG but still it misfires. 3) Spark plugs and wires have been replace, running like never before but only for a week or so. 4) Just todayI ordered a new coil to see if that would help. From this post I take I should replace the spark plugs too ????
Do you have any other suggestions ??? You have to know MB dealers, including the one I bought the car new with, are acting very strange, because the car has this LPG installation. It's not an original MB anymore, you see (their point of view). The care never did run very smooth (275.000 km in 4,5 years) but a few weeks ago with the new plugs it felt better than new, was running better on LPG than on petrol in the past. I WISH I FOUND THIS PLACE EARLIER. Thanks for any comments.
Greetings from Belgium
Nico