Lewissodeh

Hey guys, looking for some advice.

So about a week ago my car 2015 c300 40k miles started acting funny on idle. I drove it to work and the check engine light started to blink then stayed on and the car ran like poop. I scanned the code it was a cylinder 4 misfire, I changed the 4 plugs and 4 Coil packs, the car ran fine for the first 10 miles then did the same thing. I was able to drive it home and park it.

I purchased the parts from my local Mercedes dealer. What could be the issue ? The car has always been serviced at the dealer, no mods. I put 5k miles on it a year.

The car shakes badly also. Its been sitting in my driveway for about 2 weeks now untouched.

My warranty just ended.

Please and help will be appreciated. Thank you

LaciCLK320

Wow, l hope it is not a broken piston, wrist pin issue. Do a search on this as there is plenty of comments on this subject! Keep us posted!

Keith66

My first thought is; when you pulled the original plugs, did #4 look different in any way? Specifically around the center electrode, ground electrode and threads. (i.e.; was #4 darker or lighter in color than the rest?)

Also, did the ECM report a misfire event that occurred after you changed the plugs and coils?

Lewissodeh

All the plugs looked normal when I changed them.

I replaced the plugs and coil cleared the lights then took it for a drive, The car was fine for the first 10-20 mins then started to misfire. Yes the light went back on.

The car splitters on idle you can feel it but it comes and goes, when driving you dont feel it, drives normal.

some days it feels worse then others

realeric

Wow. 40k mile is a new car.

What can cause it? Fuel pressure, injector, wiring harness or connector, ground, air filter, MAP sensor, vacuum hoses, EGR, turbo or intercooler, electrical / ECU, intake manifold, head gasket, head/valve/piston, oxygen sensor…

Since it was fine for 20 mins after replacing the plug and coil, I’d rule out head/valve/piston. Since it happens at cylinder #4 and at idle, turbo/intercooler can be ruled out.

I’d check first, wiring to the injector/coil, injector #4, map sensor(cleaning only), check EGR valve, … check coolant if it’s clean (open engine oil cap and see if it’s clean).

Lewissodeh

So I brought to my local dealer today, Driving there no issues once I pulled in the lot I felt the car misfiring.

I ask about the piston - wrist pin issue I've been seeing all over the forms, He said he doesn't hear any slap not sure what means.

He said the Coil is working, The fuel injector he said works but then that cylinder shuts it down.
I told him I would like to wait for an answer, He walked up to me with the OH **** face told me its serious and is going to order me a uber home LOL GREAT.
He didn't have a loaner to give me. He told me car is too hot to check anything else and will update me tomorrow. 9/23/21

This sucks guys.

Cali4niadriver

Curious to see what they say. I’m having a very similar issue. I brought mine to the dealer, they said it needed a new spark plug. Replaced and drove fine for like 10-15 miles and started again. Weirdly enough seems to be ok when it sits for a while but can’t drive for too long before misfiring.

epaten

Which dealer are you going to?

chassis

@Lewissodeh
@Cali4niadriver

Any update? Measure compression and report the numbers back to this thread.