So my car is a few months out of warranty and I've been having a couple issues that seems to have gotten worse.

I've had a P0356 code that has come and gone for the last 3 months. I changed the coil pack on that cylinder as well as all the spark plugs. I never felt anything wrong ever so didn't think much of it.

Code wouldn't go away.

I was told by someone that it could possible be my intake manifold but was told on the forums that I'm not really throwing the right codes for a bad manifold.

Anyways, on a long drive, about an hour into it my car started to misfiring. My check engine light flashed and started to stumble.

I pulled over into a gas station. Restarted my car and it was fine again. Filled up my tank and went back home.

Ran the codes again and this time I had a P0128 coolant temp code. Reset the codes to see what else comes up.

On a short drive, my car started misfiring again. I pulled into a gas station once again and restarted my car. It still stumbled. Did it a couple times and gave it 2 minutes and it started back fine.

Now I'm home and ran the codes again. This time I got 6 codes but they were 3 repeated.

P0356
P0304
P0354

But runs fine.

Any help would be appreciated. Could it be a fuel pump or thermostat problem? Wiring harness? Coil packs?

After finally feeling my car misfire during idle, I realized that my car would do that every now and then. I felt a slight vibration when in idle and assumed that it was a motor or transmission mount but now I know it was the car misfiring. It was very gradual and never was felt when driving.

Please help, any guidance would be appreciated. I already took it to a Mercedes Benz Tech and he was the one who changed my coil pack and plugs and essentially didn't fix anything. A different tech told me its the manifold while another said its not. I'm confused.

Thanks again in advance guys.

 

Ignition coil plugs.

 

I tried swapping the coils and get the same code for the same cylinders. Any other suggestions?

 

When was the last spark plug service

 

changed them myself about 500 miles ago. Used factory from the dealer plugs.

 

Did you ever find the misfire issue - my 2007 E550 has similar issue