I have a 2002 E55 with 49K miles. I have twice now had a misfire on cyl 6, once in May (reset thinking it could have been a fluke) and now again 4 months later. Both times the misfire happened at high RPM (100MPH+) and both times on Cyl 6. After the misfire the engine runs rough until restarted. I have read through the misfire posts and nothing refers to it happening at high RPM and I thought that might help in narrowing down if it is the plugs,wire,coil or other? Any thoughts?

The MAF sensor is 8 months old and is OE Bosch
The Crank Position Sensor is 3 months old (suggested by dealer when in for service)

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1986 190E 186K (For Sale)
(Maroon, Tan leather)
1996 C280 Sport 208K
(Brilliant Silver, Black Leather)
2002 CLK430 Sport 45K
(Brilliant Silver, Gray Leather , Birdseye Maple)

Have you tried switching coil to different cylinder?

Have you installed new plugs? MB reccomends every 5 years OR 100K (5 years was up 2 years ago)! which ever cones 1ST.

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Retired Moderator

I have not yet replaced the plugs. I am going to order parts + plug wire tool based on suggestions here. I have read the OE equipment is NGK ($2.99) plugs on the 2002 E55. Is that correct? I have a hard time believing in the $13 "premium quad platnium plus" plugs. On a 16 plug car its a $160 difference so before making that purchase I would like to know if the NGK's are the correct plug?

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1986 190E 186K (For Sale)
(Maroon, Tan leather)
1996 C280 Sport 208K
(Brilliant Silver, Black Leather)
2002 CLK430 Sport 45K
(Brilliant Silver, Gray Leather , Birdseye Maple)

Bosch, Beru, & Champion are OE on that car.

Bosch FR8DPP33+ (7422) would be my choice. $5-6 would be a good price.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Hi, at this mileage, around 50000 I think the likely hood of plugs being the issue isn't as great as other things. It is cylinder specific so that makes it easier. We can do a lot of guessing but you can also take it to a dealership that has the MB diagnostic system. Plug wires are a big issue with that engine group. There is a test that allows a technician to shut of one half of the ignition system and watch the other half function. As you mentioned there are two plugs per cylinder and of course two wires. The wires were around 60.00 per so it gets costly. If there is a secondary insulation breakdown it will cause misfire at high ignition loads. The mileage is a bit low for this problem but it's worth checking as it can get quite expensive quickly just in parts. At 80000 miles when they started with a misfire on one or two cylinders we recommended replacement of all wires or the car just kept returning with another failure starting in a cylinder not yet addressed. The coils can also be an issue, I have changed a few but no where near as many as plug wires. If you look in a tool manual you should be able to locate a valve adjusting wrench for an older 110 motor, it seems to be the universal plug wire removal tool. It hooks under the end on the insulator and levers the wire up and off. The two rear cylinders on this engine are just a bear to got off sometimes.
Bill

Ok, its been awhile, but since the first post, I have since changed all the plugs, changed all the wires and two weeks ago changed the coil pack for cylinder 6. I am still getting the Cyl 6 Misfire if I get the engine to 5,500 , 6,000 RPM. Its always only Cylinder 6? Need some help if anyone has an idea.

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1986 190E 186K (For Sale)
(Maroon, Tan leather)
1996 C280 Sport 208K
(Brilliant Silver, Black Leather)
2002 CLK430 Sport 45K
(Brilliant Silver, Gray Leather , Birdseye Maple)

Not sure of the NA 55 5.4L but the 55K 5.4L had a software issue that would pull a cylinder misfire code and CEL under hard acceleration.

Does the car go into a low power or limp home mode when you get the CEL and then clears up on a restart but holds the CEL?

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1971 280SL ROADSTER
1988 300CE TWIN TURBO WIDEBODY
1994 E320 CABRIOLET
1999 C43 AMG
2005 G55K AMG
2008 CLK63 AMG BLACK SERIES

It sounds like a partially clogged catalytic converter to me. I've seen situations identical to this one more than once.

If the cats' have been previously replaced, check for pieces of the old ones stuck in the pipes downstream. I've seen this on a few occasions as well.

Any luck? I've got a very similar problem. Would like to discuss if still relevant to you.

don't no matter how temping every put Armoall on plug wires.Or clean engine with it,as rain will dilute it

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

I had the exact same issue with my 00 210 E55, it would run fine then if I got to a certain RPM (4-5K) it would start to run rough and the check engine light would flash. My indy tried replacing the coil pack, tested the pressure from the fuel pump, and never could find what was wrong with it. Had the code reset and traded it at the dealer for my 211. Was a very weird issue but I thought maybe the CC was plugged somehow.

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2001 G500 (45k and counting)
1991 350SDL (211 and counting)
1998 C43 (50k) Silver/Black (sold)
1995 E500 (40k and counting) Pearl Black/Anthracite (sold)
1991 300CE (50k and counting) Silver/Black Cloth (sold)
1983 300D - 79k Classic White/Blue Leather
2002 E55 Obsidian Black/Black
1996 S600 Coupe - 75k Black/Black (traded)
1984 300D -145k (sold)
Silver Blue Metallic/ Blue Leather
1985 300D - 87k (sold)
Manganese Brown/ Palomino Leather
2005 E55, 50k(sold)
Flint Gray/Black

I bought mine a couple of years ago. Its a 2.6L petrol twin-cam v6. Picked her up a good few miles from home so thought I'd see how she felt. Thought she just slowed down a bit approaching 100MPH. Then there was a sudden shudder and the CEL came on. Stopped and felt the engine running rough in idle. Switched off and on and it was fine - CEL still on.

Called the seller. He said car was reporting a CPS error code so he had just had the CPS changed. So I should see how it behaves and if it happens again to let him have the car. CEL went off after a few ignition starts. A few days into it and the weather changed drastically. We had heavy frost and guess what? - the next day the car wouldn't start! Cranks fine, just no catching. Let her crank a few times and nothing would happen. Then, a few minutes later, crank and it would catch fine. CEL would come on, but otherwise car would perform fine. All day. No problems at all when hot.

Tried the 100MPH thing a couple of times and both times same as above. Note that the RPMs don't matter. I can easily rev up to 5k rpm in town on kick-down. Never a problem. The engine needs the added resistance offered at sustained speed.

By now I was so used to the cold start problem. Frost the night before (car is parked out on the drive) and current temperature between 3 - 6C and it would not catch. Of course, until it wanted to (every time exactly as above). If it was over 6C or it was below freezing, it would not have a problem starting cold.

Anyway, gave the seller the car. He said the CPS code was still there so he had the CPS changed again. Sorry but he couldn't remember the exact code number.

I did not have the starting problem after that.

It was next year (I go away for long periods) that I got her out onto the motorways again. Cruised at 120MPH for a good 40 miles, with speeding up to 130MPH. No problem.

All that year, no starting problem (through frost n all).

3 days ago, frost first time this winter, ... yep! cold cranking no start issue again.

Now, first time around, I had to come up to speed with info on the electronics on these engines. Couldn't have done this without these forums. PLUS, I have time on my hands - this is like a vacation car so not used much. I went through the Battery, MAF, plugs, petrol supply, ignition etc discussions but just couldn't see a problem here. And since the CPS change seemed to fix the issue that was the end of it.

SO - this time around, I think I will pursue it as a CPS issue, although not the sensor, but the connections. This does explain the frost-only reaction as frost, in the process of melting, may accentuate a bad connection or affect an exposed connector/ split insulation/etc. This, I think, would also explain the high speed issue since a bad connection can cause an ever-so-slightly mistimed CPS signal to distort enough at high revolutions, under load, to provide a mistimed spark trigger from the ECU.

3 days ago when the no start issue came up I didn't keep cranking. Instead I opened the bonnet and tried to reach for the cps connector. It was night and I don't think I reached it but did ruffle the wiring running in that area. Well, the next crank started the car!

2 further tries and it starts first crank (although the crank does go on for longer than normal). I think I'll check the wiring properly at the weekend.