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So my car just left me stranded today, started misfiring and became undrivable. After a small acceleration, the check engine started flashing and as I slowed down, the engine started misfiring. I pulled over and checked the codes which were multiple cylinder misfire and P3000 , P3001 , P3002 .. These are the only codes the car is giving me, I did not see anything visually wrong with the engine.
I can start it but it barely revs up, almost like a whole bank just stopped working. I'm not sure where to start, it seems to be affecting Bank 1 or 2 since it would still run or 4-5 cylinders, now it feels like its running on 3. Any help would be appreciated.
So after some more diagnosing today, I cannot get the car to give me any other codes other than misfires... I did a compression test with my Xentry and it doesn't look good. It appears 5 out of 6 cylinders have around 100 PSI and cylinder 4 is maintaining 200+ psi.. I'm really curious how a perfectly running engine can just lose 100psi on 5 out of 6 cylinders all at once.
Xentry is telling me to do a leak down test on all cylinders, did all my valves just bend?
Last edited by W204Motorsports; Mar 8, 2020 at 04:33 PM.
I am curious what you ended up doing with your car. I have one with similar misfiring issues. Finally took it to a mechanic who says that I need to replace one of the cylinder heads as the valves on two of the cylinders are burnt. Don't understand why this would have happened on an engine with only 68k miles on it.
I had an engine that was misfiring on multiple cylinders on one side of the engine, it took a while to figure out but once I checked the timing thats when I started getting somewhere. You can pull out all 4 cam sensors and turn the engine over to the 305 mark on the crank. There are timing marks on the camshaft actuators that should line up with the cam sensor holes. This tells you a lot about your engine and does not take long to do.
timing marks are shown in the first minute of this video
On the engine I was working on, checking the timing marks lead me to this discovery. The drivers side exhaust cam pulse wheel (right side of pic) had a big piece break off. When I found the piece it had the impression of the gears between the intake and exhaust cam adjuster so it looked like part of it got caught in between them. That whole event damaged the exhaust actuator internally (all the teeth were fine though somehow) and the actuation was jammed in one direction so I swapped that and the car ran great, there is a bad noise on start up that goes away and an engine light that is triggered in 2 start ups so I am sure the intake adjuster is internally damaged also but I would have to take off the timing chain to swap that one out. Its a 197k miles parts car that had a lot of metal shavings in the oil so thats as far as I will go on that engine
I had an engine that was misfiring on multiple cylinders on one side of the engine, it took a while to figure out but once I checked the timing thats when I started getting somewhere. You can pull out all 4 cam sensors and turn the engine over to the 305 mark on the crank. There are timing marks on the camshaft actuators that should line up with the cam sensor holes. This tells you a lot about your engine and does not take long to do.
On the engine I was working on, checking the timing marks lead me to this discovery. The drivers side exhaust cam pulse wheel (right side of pic) had a big piece break off. When I found the piece it had the impression of the gears between the intake and exhaust cam adjuster so it looked like part of it got caught in between them. That whole event damaged the exhaust actuator internally (all the teeth were fine though somehow) and the actuation was jammed in one direction so I swapped that and the car ran great, there is a bad noise on start up that goes away and an engine light that is triggered in 2 start ups so I am sure the intake adjuster is internally damaged also but I would have to take off the timing chain to swap that one out. Its a 197k miles parts car that had a lot of metal shavings in the oil so thats as far as I will go on that engine
Well if you need camshafts I still mine laying around I can donate, they had no damage but if you're saying there's metal in the oil and with close to 200k miles, its obviously not worth fixing when there are so many low mileage units available. I never really figured out exactly what was wrong with it, I still have the engine sitting apart and the only thing left is to remove the cylinder heads and inspect cylinder 4. Mine had similar mileage when it failed and I didn't have time to mess around with it at the time nor was it cost-effective when there was a 2012 3.5L with 50k miles from a glk350 available at my local scrapyard for 1000$. I put over 20k on the 3.5 since and its definitely a nice upgrade.
Last edited by W204Motorsports; Dec 19, 2020 at 04:40 PM.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
