Help:P0304 error code. At dealer for 3 weeks
Thread Starter
Newbie
Joined: Dec 2005
Posts: 2
Likes: 0
Help:P0304 error code. At dealer for 3 weeks
Hey guys. Really need some help. I have a 2006 ML 500 with 75k on it. My dad drives the car daily and is a bit soft on the car. I drove it for a week a bit heavy and now I have the check engine light on. I scanned it and got P0304. Cylinder 4 misfire. Car runs slower and shakes crazy at idle. I have an extended warranty that is good. Before I took it in I replaced the plugs and wires with oem parts and that didn't fix it. Dealer replaced the injector and the ECM computer. Still on. They swapped the ignition coil to a diff cylinder and still the same issue in cylinder 4. My service tech feels there is carbon build up in the engine causing this. This issues comes and goes. I am annoyed as it's been there for 3 weeks. Any ideas on what it could be? I need help. Thanks guys
Junior Member
Joined: Nov 2013
Posts: 63
Likes: 6
From: Northampton PA
99 E 300TD, 02 E320, 2013 ML350
Some techs approach the diagnosis in different ways. Before replacing the computer they should have used a borescope to check the cylinders for any damage/scorring. Not saying they didn't do that just letting you know my opinion
Junior Member
Joined: Nov 2013
Posts: 63
Likes: 6
From: Northampton PA
99 E 300TD, 02 E320, 2013 ML350
If they keep replacing the same stuff they obviously don't know what they are doing. I would hope they have done a compression test. They should have also done all the wiring checks so this sounds like an internal issue. This could be cylinder scorring, rings not sealing or a valve issue. Like I said in the first post, they need to borescope the cylinder and check for wear/damage. Hope this helps. btw, where are you located?
