Moekluse

Hello everyone, this is my first post here on the MB forums but I've seen dozens and dozens of in depth forums that I refer back to every so often. I have a 2006 SL600 with 92,xxx miles on it that I just recently purchased and I'm running into some issues. I am not a mechanic by trade, I am a 19 year old that has been working on European vehicles for 3 years, mainly mini coopers. I do timing chains, head jobs, stroker motors, custom tig fabrication and more. This is my second ever Mercedes, and the can/bus systems on these vehicles are much touchier (TOUCH-EEE-ER?) than their former European counterparts.

Long story short I was getting 7-12 misfire codes. Tested coil and found to be bad. Bought a new coil from dealer and that bank was up and running. Did a compression check on all 12 cyl and averaged 180 psi. Leak down showed great results as well. I then began receiving misfire codes for cyl 2,3,&4 so i automatically assumed the passenger side coil was going out as well. I purchased new ones (did all 24 spark plugs while I was at it) and the car ran on all 12, but it was not boosting. I also replaced the crank shaft position sensor while I was at it as well. I temporarily installed a cheap manual boost guage and engine was only running on vacuum, no boost. I checked all the lines leading to the bypass valve in the front of the turbos and found no issues. I actually ended up re-hosing the whole vacuum and evap hoses (except hard lines above turbo of course) and it made no difference. Once the car was up to temp it was running smoothly, no boost but smoothly. I shut it off and reset the codes with my Autel maxidas ds708 and fired it back up and cyl 2,3, and 4 were misfiring again (no engine light found through smooth running values). I found the maf on the right airbox disconnected, so I reconnected, cleared codes, and let the car cool down for 2.0 hours and fired it up and it ran smoothly, but gave me misfire codes on those same 3 cylinders but it was not misfiring according to my smooth running values and my integrated butt vibration detector.

I also found a crack in the map sensor above the throttle body which I believe has a big deal regarding the boost issue causing the limp mode. Ordered a factory one from the dealer.

My next suspect for the semi rough running is that those injectors may be clogging up or possibly my right hand side catalytic converter is clogged up and creating back pressure in the right bank causing a rough idle when warmed. But it's most likley not because it runs great until I shut it off and restart when hot.

Please ignore my ignorance as I am not very familiar with these vehicles. My plans after getting it running properly are to fabricate a top mount turbo kit and run the car on AEM infinity in the future after a black series body kit.

I really appreciate any and all comments, thanks!

Moekluse

Cold start up this morning, no misfires at all but not boosting. Is there any way to bypass the bypass valves to manually boost the engine?

arsupisemnet

There is no boost on the idle for most MB engines. Wastegate normally open and closed by actuator during driving. Check the boost under load while driving.

Moekluse

Thank you for your message, re attached mechanical boost guage and it was making 5-6 psi under load. At no point did it make more and I was driving it pretty hard. I did not have a misfire and I tested it in dyno mode as well. Everytime I got off the pedal, the bypass valve was rushing out air quickly, it was a very obvious sound such as someone blowing through a straw. Never driven any other sl600 but they probably dont make that sound originally. My new map sensor will be here tomorrow, hoping it will bump boost back up. Will update tomorrow

Moekluse

I got the new sensor in from the dealer and installed it, no misfires and ran great. Took it down the street and went pretty hard on it and got it sideways a few times and it was running great, def took care of my boost issue. I only drove it a mile and took it back home, when I parked it, it began misfiring, cyl 2,3 & 4. I have a feeling that the injectors are failing once the engine gets to temp because it hauls *** when the car is cold. I'm going to swap the left and right bank injectors tomorrow to see if the misfire spreads to the driver side so I know if I need to order new ones. There are much smarter people on this forum than me and I would really appreciate any input as I may be overlooking a simple issue. Thanks!

jgcsl600

Check you fuel pressure

Sl600kd

hey i have similar issues at times (one minute my check engine light come on, some times i dont see it for days) but my problem is my intercooler system is temporarily disassembled. but these are the things that contribute to boost problems

1) YOU NEED PREMIUM GAS 93+
2)CHECK ALL VACCUM LINES (MOST PEOPLE LINES ARE BRITTLE) (I HAD ABOUT 5)
3 MAKE SURE THE CLAMPS ARE VERY TIGHT ON THE TURBO TO INTERCOOLER
4)CHECK AND REPLACE BOOST SENOR (I SEE YOU DONE THAT)
5) USE THE RIGHT HEALTHY SPARK PLUGS
6) PROPERLY BLEED THE INTERCOOLER SYSTEM (WHICH IS ACTUALLY A DIFFICULT THING, AND MANY HAVE TO OFTEN DO IT)

But your problem sounds like a number 6, get a code reader and check intake temps, ideally the temps should be under 70c, (mines can go up to 90c) and its drastically cuts boost usually if you in a stop and go scenario, and driving it hard. But the highway give you the boost as needed.

But look up m275 intercooler bleeding (this has been a big issue for all twinturbo v12 mercedes), some people just live with it, I'm almost at that point, it will boost when it want to boost, it still faster then most sport/muscle cars i will come across.

Moekluse

Thank you for your reply, I got the boost issue sorted out. I took the car out and it felt awesome, spinning all the way through 3rd gear, could barely keep it straight. Then, as soon as I pulled into the house and the temp reached 80c and I was met with misfires. I swapped injectors over and the misfire travelled to the opposite side so I have multiple injector failures. I used my stethoscope and on the good injectors could hear the ticking of the injector pulsing, but in cyl 7 it sounded very muffled/ no ting to it. I wonder if heat is responsible for the injectors failing once warmed up

arsupisemnet

Maybe clean injectors and check wiring?
As your engine warms up fuel pressure could me going lower due to weared out fuel pump. Check fuel pressure on cold and warm engine. Also on warm engine press accelerator and see how much of the drop in fuel pressure you have.

Moekluse

Found multiple bad injectors. They stop opening once they are warmed up

George993

And don't forget to check the voltage transformer which sits on the top of the engine. Swapping it takes only a few minutes. Often all the coil pack/plugs/injector etc replacing just makes the problems move around or come and go without getting solved. Then you replace the voltage transformer and all is fixed (ask me how I know :-). In my case the troubleshooting took twice as long as the first replacement transformer was still bad and only a second one fixed the problems.

BTW, no point getting expensive ignition parts from the dealer or used parts from ebay. Just go to v12icpack.com for all your ignition problems, Clark will even loan you coil packs or voltage transformers to check if a given unit is really the problem

Moekluse

Definitely going to check the voltage transformer, but I overlooked something very simple. Upon checking battery voltage after the car was warmed up and misfiring. I found that it was only producing 12.6 volts which is clearly not enough to fire those coils. I charged the battery over night and it ran great the next day, but the voltage was slowly dropping. I want to warm it up today and beat on it to replicate the misfire so I can check voltage again. Most likley looking at an alternator unless the voltage transformer has anything to do with that. Thank you

imtheking

You're 19 with this much-advanced knowledge?

I'm impressed

George993

So likely the alternator. I don't know that part of the Mercedes very well, but in other cars such symptoms can also be simply a busted alternator diode - so fixing the problem could mean soldering in a $0.50 diode or replacing the diode circuitry with another one (diodes are easy to test). Unlikely the elektromechanical parts of the alternator going bad with such low mileage, but the notorious V12 heat could damage the diodes or alternator voltage regulator.

Your experience is not unusual, those are very complex, very interconnected and very poorly understood cars. So often a simple single problem can not be identified and the mechanics/dealers replace tons of stuff with $10k+ bills, often with the original problem still persisting after all the changes.

Good luck :-)

George993

That's why anyone owning V12TT needs to either become an expert with those cars or to have a very thick wallet, regardless of the car purchase price

Sl600kd

Yeah exactly, you gotta be a car fanatic or some one likes burning cash

ponchik

well, so far it was rather cheap. 300USD for coil pack repair, 300 for the voltage transformer. Plus 300 for spark plugs replacement. Looking forward for another 600 for engine mounts replacement. Not that bad for 30k km.

Though i still have to pay for this SBC unit.

ponchik

Where did you connect to check the voltage? the battery is connected through some control unit, so it may be that the battery voltage is different from what alternator produces.

If alternator does not charge, you would inevitably have dead battery over time, which you don't have. And no charging will get your battery over 12.6 volts.

bobterry99

The rear battery is connected directly to the alternator; the front battery generally connects through a control module.

Moekluse

Update. Running into some strange issue. When the car is cold it runs great and I beat the absolute s$!# out of it. I'll beat on it for 15 minutes and come back to the driveway, let it sit for 25 seconds and it begins misfiring. Voltage remains 13.6 after I charged it. How would i go about testing the voltage transformer? Does that sound like the possible issue? Thanks again

arsupisemnet

Temperature sensors?

ponchik

I don't think there is any way to test voltage transformer except for replacing it with the working one and looking at the result.
It produces 180 and 30 volts out of 12 volts supplied by the alternator.

But if you found bad injectors, maybe just start with them?