mcr

2006 CLK350 idling and driving rough, pulled code P0301, which indicates misfire on cylinder 1

how should i proceed if I want to DIY? should i replace coil and see if it goes away, then replace plugs if needed? spark plugs have 5 years/60k miles on them

also, what brand is the OE coil? i see Delphi coils available in stores, but there's a more expensive Bosch coil that's only available online

OR-CLK350

I would start by changing all the spark plug and inspect them, erase codes. I think 5 years is what the manual recommends. If the code comes back, then replace the coil. I personally would check the cost of the coil at the dealer.

Fatz

You can swap the coil and/or spark plug for cylinder 1 with those of another cylinder and see if the problem follows the coil/spark plug. you can swap both the coil and plug at once and if the problem follows the coil/plug originally in position 1, you can just replace both. I would swap them one at a time, starting with the coil.

When I replaced my coils and plugs about 50K miles ago I used Delphi coils and Bosch plugs.

mcr

you replaced all coils? that's not a cheap thing to do, especially if they're working fine. aren't they supposed to last for the lifetime of the vehicle? i've only ever replaced one coil, and it happens to be on cylinder 1 too, so i'm thinking these aftermarket coils, regardless of brand or OE label, aren't as good as what they ship to mercedes

Fatz

4 of my coils were bad (2 cracked 2 intermittent ) when I changed them all. I had a catastrophic radiator failure that caused me lots of problems. I also eventually replace the wiring harness and ECU. And the car doesn't suffer from a lack of exercise. I think that work was done between 120K and 140K. It is near 200K now....

mcr

I've always loved the clk/e550/63 but the cost of struts is an additional concern with those. do you replace them often? diy? what do they run you?

also, if i pull out the ignition coil, can i tell it's bad just by looking at it? if so how?

Fatz

My car is lowered (H&R) and I changed the struts after running the car lowered a couple years on the OE struts. Installed Bilsteins (B8).

You can inspect the coil for cracks in the epoxy housing. You can sometimes detect where a defective coil arcs. But, if you swap it to another position and the error code follows it, that's all you need. If unsure, you can double check by moving it to yet another position or back to the original and noting the error message.