random misfire any suggestions?
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Member
Joined: Jun 2009
Posts: 189
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ML63, e550 cabrio
random misfire any suggestions?
my 2001 S600 has a misfire comes on when car is at operating temp, only at idle in gear at stop light. goes from right bank misfire, to left bank misfire or both. turn engine off restart, no misfire. sometimes when you turn off and restart CEL goes away. coil packs, transformer, spark plugs, map sensor, air change over valves have all been replace plus ECM has been checked/repaired. any clues? anyone? 
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Joined: Dec 2012
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From: Ball Ground, GA (N of Atlanta)
2003 S500 2007 GL450
While we tend to assume that every problem is a computer problem on our cars, there are times when the problem is just a normal car problem...
Check carefully for vacuum leaks. While it is usually a safe assumption that any 928 owner knows how to check for vacuum leaks,
get a 4' piece of rubber or plastic hose, stick it in your best ear, and probe the idling engine for a hiss. Stay away from moving and hot parts!
Get a couple of large bottles of Techron (the expensive version) and run it for a couple of tanks of fuel to clean the injectors.
Open the hood in the dark and watch and listen for spark going to ground on the coils or plug wires.
Is the oil due for a change? Sometimes, the intake valve stems will build up deposits and tend to drag just a little as they close. That should not be the problem with the proper oil, changed at the proper intervals.
Check carefully for vacuum leaks. While it is usually a safe assumption that any 928 owner knows how to check for vacuum leaks,
get a 4' piece of rubber or plastic hose, stick it in your best ear, and probe the idling engine for a hiss. Stay away from moving and hot parts!Get a couple of large bottles of Techron (the expensive version) and run it for a couple of tanks of fuel to clean the injectors.
Open the hood in the dark and watch and listen for spark going to ground on the coils or plug wires.
Is the oil due for a change? Sometimes, the intake valve stems will build up deposits and tend to drag just a little as they close. That should not be the problem with the proper oil, changed at the proper intervals.
Junior Member
Joined: Feb 2013
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From: Ipswich
vw golf gttdi
do you have any codes?
what quality of air mass sensor is fitted?
are the oxygen sensors switching?and make sure they are plugged into the correct side as ive come across this before!
what quality of air mass sensor is fitted?
are the oxygen sensors switching?and make sure they are plugged into the correct side as ive come across this before!
Thread Starter
Member
Joined: Jun 2009
Posts: 189
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ML63, e550 cabrio
just to update everyone, especially the tower of knowledge, tusabes IMO tusabes nada, i went back to the starting board and replaced the spark plugs with autolite platinum plugs total $70, and now everything is OK, smooth idle, no misfire and not CEL. Now, i must quickly dump the heap on someone before it does it again...............
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From: Montreal, Quebec
2009 E350 4M Avantgarde;mistress 2002 S600; wife 2014 C300 4M
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From: Welwyn, Herts, UK
2006 S600
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From: Near St. Louis, MO
S 600 2003
there is a ECM software update that helps with the random misfire at idle. My 03 S 600 is now known as "Lucifer". fast as hell and pure hedonism - UNTIL IT ISN'T. Just did both coilpacks and plugs. Now the ABC light came on this morning. I think I will park it and drive my GTO for a while. Grrrrr....
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Joined: Sep 2012
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From: Montreal, Quebec
2009 E350 4M Avantgarde;mistress 2002 S600; wife 2014 C300 4M
I get intermittent CEL(comes and goes) for intermittent misfire #12 cyl, but I never notice it as power loss. The odd "mini" shake at idle, but nothing drastic.
Anybody know what the ECU update is, and to what V12 engines it applies?
thnx
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Joined: Jun 2012
Posts: 29
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From: Near St. Louis, MO
S 600 2003
I found a MB dealership with a service manager who was actually a mechanic for 20 years, so I feel very lucky. 
Most MB dealerships seem to have shirt and tie guys with no knowledge at all whose job seems to be bull****ting people.
But I digress...
We were talking about my S600 and he mentioned the software update and that he put it on one of the newer models as well as mine - a v12 biturbo - and that somehow it cured a problem at idle with fuel getting too hot in the fuel rail. I don't know how that sort of heat build up can be moderated with a software update, but I will ask him.
I have other cars, and my own shop - the S600 is really way to complex for me to do much beyond basic maintenance. Although I found changing plugs to be a real pain in the A**.
I also found that plug gap is critical with this engine - way more sensitive to than the small block GM engines I mess with.
Most MB dealerships seem to have shirt and tie guys with no knowledge at all whose job seems to be bull****ting people. But I digress...
We were talking about my S600 and he mentioned the software update and that he put it on one of the newer models as well as mine - a v12 biturbo - and that somehow it cured a problem at idle with fuel getting too hot in the fuel rail. I don't know how that sort of heat build up can be moderated with a software update, but I will ask him.
I have other cars, and my own shop - the S600 is really way to complex for me to do much beyond basic maintenance. Although I found changing plugs to be a real pain in the A**.
I also found that plug gap is critical with this engine - way more sensitive to than the small block GM engines I mess with.
Super Member
Joined: Sep 2012
Posts: 690
Likes: 76
From: Montreal, Quebec
2009 E350 4M Avantgarde;mistress 2002 S600; wife 2014 C300 4M
[QUOTE=Nardulli;5609081]
But I digress...
We were talking about my S600 and he mentioned the software update and that he put it on one of the newer models as well as mine - a v12 biturbo - and that somehow it cured a problem at idle with fuel getting too hot in the fuel rail. I don't know how that sort of heat build up can be moderated with a software update, but I will ask him.
Since I have an intermittent cyl# 12 misfire at idle, I am very interested as to what this ECM software might be; my very willing factory dealership claims there is no ECM software update applicable to my car.
Could you perhaps find out?
thnx
But I digress...
We were talking about my S600 and he mentioned the software update and that he put it on one of the newer models as well as mine - a v12 biturbo - and that somehow it cured a problem at idle with fuel getting too hot in the fuel rail. I don't know how that sort of heat build up can be moderated with a software update, but I will ask him.
Since I have an intermittent cyl# 12 misfire at idle, I am very interested as to what this ECM software might be; my very willing factory dealership claims there is no ECM software update applicable to my car.
Could you perhaps find out?
thnx
