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CLS550 Master Lease, 1990 300zxTT, 2000 camry
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Discussion Starter #1
Hey people I need another opinion of a vehicle I am working on. It is a 2002 c240, I am getting a misfire on cylinder #6 that keeps returning and I am running out of ideas. So far I know that I have a good ignition coil and suppressors on the cylinder, it also has good spark plugs. The fuel pressure, fuel injectors and the fuel itself is known to be good. I have performed bore scopes on the cylinders and found no damage or carbon buildup. Cylinder leak down test got 2% leakdown with 169psi on compression. I also know that I have a good MAF. I also know that the problem is not mechanical as the valves and cam are fine. I have to be overlooking something so any help would be greatly appreciated. Thanks in advance.
 

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C230K Sport Sedan
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5,368 Posts
Did you swap parts, like swap the fuel injector with another cylinder, or swap coil packs or swap plugs? It's got to be something. Injectors or coil packs can have intermittent problems that don't show when you test them individually but if you swap them and drive the car, the code may move to another cylinder and then you found the problem.
 

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2002 C32 AMG
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From reading your post it definitely seems you know what your doing. However, I must ask, because you didn't answer Buell... Did you swap, or replace the spark plug? It can appear fine at the electrodes, but have an internal defect.
 

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CLS550 Master Lease, 1990 300zxTT, 2000 camry
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Discussion Starter #5
I did answer him lol. Yes I did swap the coils suppresors and injectors around and the misfire stayed on cylinder #6. I tried a couple more things yesterday before I took a break so I am going to see what happens this morning.
 

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CLS550 Master Lease, 1990 300zxTT, 2000 camry
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361 Posts
Discussion Starter #6
UPDATE:
Ok so I put a new crank position sensor in the car and have started relearning the sensor gear adaptation. At this time the car is running much smoother and the misfire appears to be gone. But I have to finish the adaptation before I will know for sure. I will update if it is fixed.
 

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CLS550 Master Lease, 1990 300zxTT, 2000 camry
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Discussion Starter #7
Alright back to square one rofl. The problem seemed to be fixed until I drove the car home last night and the misfire came back just as bad as before, still only on cylinder #6. So time to do some more hunting.
 

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2002 C32 AMG
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1,771 Posts
You might have a short on the wiring leading back from the coil pack if swapping, and everything didn't switch cylinders...
 

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C230K Sport Sedan
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5,368 Posts
Or a harness issue with the injectors, they make a repair kit for this purpose. Here's the description at autohausaz.com -

Bosch Fuel Injector Repair Kit; Terminal Repair Kit For 2 Prong Bosch Injector Type Plug
Miscellaneous usage as required, please verify plug on existing parts. For repair of female harness plug, for attachment to 2 pin male prong fuel injectors and similar 2 pin Bosch connectors. Kit includes 1 terminal with wire spring clip, 1 boot and 2 wire ends (female). Limited availability - $7.83
 

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W210.265/2001, W220/S500/2000, Porsche 997 C2S/2006, GMC K1500/1992
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2,157 Posts
Replace the #6 spark plug wires. Have u try that ?
 

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Misfire Merc c200 reg 2004

Hi, Just wondered if anyone has a solution to the Misfire on Merc's. Mine has 53,000 on the clock and misfires when stopped at lights or in traffic. The misfire can be stopped by turning the engine off and restarting again but the ECU light remains on and its a misfire again when stopped at the next set of lights. Have done all the things that have been listed above. New coils packs, new plugs,checked wiring, no oil in connection to ECU, taken head off, checked all injectors, all cleaned and seated correctly. Did find a cracked exhaust valve but it has not cured the problem.
the fault is always shown on # 4 have moved then all around but its still shown on #4. Evens changed the MAF sensor but its still misfiring......

Any ideas would be a great help:crybaby2:
 

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2004 C230 Kompressor Sport Coupe
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It's probably valve carbon, since that's the M271. Search for threads on M271 Valves and you will find lots of info. There was recent modest success with GM Top Engine cleaner, but if it's bad enough the head will have to come off. You have been using top grade fuel, right? It is supposed to be much worse with the lower test fuel.
 

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Have taken the Head off and yes carbon deposits but all cleaned and put back together. She does run like a dream now until stopping in traffic, engine management light comes on and then she misfires.............
 

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2004 C230 Kompressor Sport Coupe
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If compression is good, it's down to the other two parts of the combustion triangle: fuel or spark. Check the compression, swap coils, swap injectors, in that order. The only other outside chance would be something timing related, which means CPS, but that usually results in random misfires or no-start conditions.

I know you have done all this stuff so now it's about checking your own work to make sure you have not missed something. It is extremely unlikely that there is a computer problem, the cylinder #4 misfire is likely an accurate code. Of course if you can scope the car to check that for certain then you will know if it is a computer problem.
 

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Hello! Did you found what was wrong? I have exactly the same problem with a car im working with. Good compression, good fuel pressure, good maf. Tryed with new injektors, new ignition (coils htcable and sparkplugs) new cp sensor

Accidently after i changed fuel filter the car ran for about 10min on cyl 6, after that when i put some load on the car, the 6cyl was dead again.

/Martin
 

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I too have this unknown/unfound misfire issue. I replaced all plugs, all wires, most coils (including the one that is on the misfiring cylinder), and the CPS.
I keep getting P0302 once the engine is revved past 3000 - 3500 RPM.
:surrender:


FIXED! FIXXED! FIXED!
After spending too much time on this particular C240 and getting nowhere, compression checked out, etc. I fixed it. The answer is to DRIVE LIKE AN ASSHOLE!! Yup. Put it in second, kept it up at 4-5k rpm and kept the scanner hooked up. When it would throw the code, I'd clear it immediately, then pull over stop and restart the car. After a few times doing this, I realized the check engine light was not recurring. I hypothesize the it was carbon on the valves. I guess it blew out during my madman drive. So, try that.
 

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My 05 w203 (m271) was just diagnosed with carbon build up on the exhaust valves, #3 misfire, etc. Had it cleaned and ran it at high RPM for 10 minutes or so and it cleared the codes and runs much better.

There is a service bulletin, but it requires new injectors, valve job/rebuild, $$$$, etc. Any other solutions? Monthly italian tune-ups? Car has 70,000 miles all maintenance up to date, proper fuel, etc. I won't mention the price to fix quoted me today, as it makes me a little sick to the stomach just thinking about it...

Fairly reliable and nice car otherwise...
 

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2002 S430
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I have a 2007 C230 6 cyl. That had cylinder #6 misfire. After troubleshooting for seems like months. I replaced the fuel injector, the coil and plugs. None of that helped. I decided to test for leaks and found the intake manifold gasket to be leaking. Replaced both, cleared codes and it is running fine now! Just thought on letting y'all know in case it could be of help.
 
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