Please help me with a misfire problem
Thread Starter
Junior Member
Joined: May 2012
Posts: 49
Likes: 4
From: Shanghai, China
2004 S600 Twin Turbo V12
Please help me with a misfire problem
Hello all,
I need some help with a misfire problem on my 2004 S600.
My Star Diagnostic shows random misfires on cylinders 7, 8 & 9.
I can feel them slightly whilst sitting at stop lights.
While driving, they can be almost unnoticeable, unless I give it more than about 3/4 throttle.
Then the computer shuts down the injectors for the misfiring cylinders to protect the catalytic converters, and of course that's noticeable.
I've replaced all 24 spark plugs, 24 red insulator boots, the left side coil pack and the fuel pump & filter.
But I still get random misfires on the same three cylinders.
I even replaced the spark plugs and boots for the three bad cylinders a second time. Nothing changed.
I've not replaced any injectors yet.
This problem appeared within a day of washing the engine and has been consistent ever since.
I've also tried injector cleaner in the fuel, with no positive results.
Has anyone heard of anything like this?
Any ideas or suggestions would be greatly appreciated.
Thanks,
Drew
I need some help with a misfire problem on my 2004 S600.
My Star Diagnostic shows random misfires on cylinders 7, 8 & 9.
I can feel them slightly whilst sitting at stop lights.
While driving, they can be almost unnoticeable, unless I give it more than about 3/4 throttle.
Then the computer shuts down the injectors for the misfiring cylinders to protect the catalytic converters, and of course that's noticeable.
I've replaced all 24 spark plugs, 24 red insulator boots, the left side coil pack and the fuel pump & filter.
But I still get random misfires on the same three cylinders.
I even replaced the spark plugs and boots for the three bad cylinders a second time. Nothing changed.
I've not replaced any injectors yet.
This problem appeared within a day of washing the engine and has been consistent ever since.
I've also tried injector cleaner in the fuel, with no positive results.
Has anyone heard of anything like this?
Any ideas or suggestions would be greatly appreciated.
Thanks,
Drew
Super Member
Joined: Feb 2009
Posts: 780
Likes: 11
From: Dallas, TX
Range Rover
After replacing everything are you still getting a check engine light? This sounds similar to an issue I had with my first ml. I got jump started by an old car called a dart and my car wouldn't act right . Mercedes replaced plugs , coils , so much. For a month the car was in the shop. Finally replaced the entire engine harness and all was well. Turned out a resistor went bad in the harness
Thread Starter
Junior Member
Joined: May 2012
Posts: 49
Likes: 4
From: Shanghai, China
2004 S600 Twin Turbo V12
I checked the component N91, ECI Ignition Systems Mains Unit.
The N91 provides four outputs, two to each coil pack:
Primary voltage ~ 180 volts DC, and Auxiliary voltage, ~ 25 volts DC
In addition to following the testing instructions in Star Diagnostics, I also tested the four voltages with the engine running,
so that the mains unit was supplying power to the coil packs during the test.
The Star Diagnostics test procedure only checks the voltages while the mains unit is not supplying power to the load.
All four DC voltages were well within specifications.
Additionally, I checked the four outputs for any ripple or noise.
They were all very clean, with less than 50 millivolts of AC.
The N91 provides four outputs, two to each coil pack:
Primary voltage ~ 180 volts DC, and Auxiliary voltage, ~ 25 volts DC
In addition to following the testing instructions in Star Diagnostics, I also tested the four voltages with the engine running,
so that the mains unit was supplying power to the coil packs during the test.
The Star Diagnostics test procedure only checks the voltages while the mains unit is not supplying power to the load.
All four DC voltages were well within specifications.
Additionally, I checked the four outputs for any ripple or noise.
They were all very clean, with less than 50 millivolts of AC.
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Thread Starter
Junior Member
Joined: May 2012
Posts: 49
Likes: 4
From: Shanghai, China
2004 S600 Twin Turbo V12
Update: In addition to the items listed in post # 1, I've now replaced:
Inter-cooler water pump
Fuel injectors
O2 sensors
I've also checked compression, 170 - 175 PSI in all cylinders.
I still have the misfires. Any ideas would be much appreciated
Inter-cooler water pump
Fuel injectors
O2 sensors
I've also checked compression, 170 - 175 PSI in all cylinders.
I still have the misfires. Any ideas would be much appreciated
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MBWorld Fanatic!
Joined: Jun 2002
Posts: 1,284
Likes: 37
From: North Carolina
2003 S500 - Toyota Corolla (in the rain)
Apparently when you washed the engine water probably created havoc with some of the electronics on the car. These cars are not like they were years ago when you could take it to a car wash, lift the hood and spray the you know what out of it.
MBWorld Fanatic!
Joined: Jan 2008
Posts: 6,151
Likes: 533
Mercedes
The proper way to "wash " an engine these days is to wet a rag with cleaner, then wipe the rag around the non electronic parts to clean off the dust
Follow up with a different rag that's had protectant sprayed on it if you want the plastic and rubber pieces to be shiny
Always spray into the rag, Don't ever spray water directly in the engine compartment
Follow up with a different rag that's had protectant sprayed on it if you want the plastic and rubber pieces to be shiny
Always spray into the rag, Don't ever spray water directly in the engine compartment
Thread Starter
Junior Member
Joined: May 2012
Posts: 49
Likes: 4
From: Shanghai, China
2004 S600 Twin Turbo V12
imusicpro,
Did you have any diagnostic codes related to the downstream O2 sensors which indicated that the cats were defective?
Here's another interesting piece of information:
After clearing the misfire code P0300, the check engine light will not come on if I drive the car "easy" no matter how long I drive. But after the car is stopped for a short while and then re-started, the check engine light will come on after only a few minutes of "easy" driving.
Did you have any diagnostic codes related to the downstream O2 sensors which indicated that the cats were defective?
Here's another interesting piece of information:
After clearing the misfire code P0300, the check engine light will not come on if I drive the car "easy" no matter how long I drive. But after the car is stopped for a short while and then re-started, the check engine light will come on after only a few minutes of "easy" driving.
Newbie
Joined: Jun 2014
Posts: 8
Likes: 0
S500
last week , when i drive to work, the check engine on, but the car still driving fine . But when i drive home i notice loss power, check engine flash and the engine start shaking . I tow the car to the shop, they take out the spark plug, clear the code . But check engine came back only 1 day . They suggest to fix the Catalyc converter , problem solve .
