Valley996TT

My CL65 is misfiring on cylinders 1-6 when I go WOT. I have already changed the coil and voltage transformer, but still have the same problem. I'm thinking it might be the MAP or CPS. Can anyone direct me to or provide a diagram where they are located and how many of each of these sensors our V12s have? Thanks.

Dr Matt

There are 4 "MAP" sensors. There is one in each airbox that just gives the ECU info about filter restrictions. They are a different part # than the two actual MAP sensors as the air box sensors only read vacuum, not vacuum and boost. There is one MAP sensor in the intake manifold under the Transformer. There is another attached to a hose coming off the passenger side intercooler. It is mounted to the bracket that bolts down with the passenger side transformer old down bolts. As for the CPS, I don't know, mine hasn't failed, yet....

Welwynnick

Do you have a tune?

Have you changed the spark plugs?

If you have the wrong plugs or the wrong gaps, you will just break your new coil pack given time.

Nick

shardul

iTrader: (1)

put a bore scope and check for cylinder scoring. We are see this issue more and more lately.

Valley996TT

Nick,

I don't have a tune and I changed all the spark plugs. I don't think it's the spark plugs because the misfiring only occurs in cylinders 1-6 on WOT.

I suspect it's something that is dedicated to the passenger side cylinders. I also suspect that I might have a clogged catalytic converter that is creating back pressure. But, figured I would try replacing the sensors first. I looked for any hoses that might have issues (disconnected, loose, leaks, etc.) but couldn't find any. There is what appears to be a sensor on the rear of the passenger intercooler that I was careful with when I changed the spark plugs. Does anyone know what this sensor does and if it could explain the misfires isolated to the passenger side cylinders?

Thanks for everyone's responses so far.

Hector

Welwynnick

That's the boost sensor, and its often damaged by mis-handling (short pipe off the front of the RHS intercooler.

There's a long pipe off the rear of the RHS IC, which provides boost pressure for the waste-gates.




Nick.

Welwynnick

Which spark plugs did you fit? What part number?


Nick

TwinTurboTim

If you want to pm me and I walk you through it. You need to isolate it to why 1 Bank is running bad. I think checking for restriction at Cat is a good place to start. I would also look at fuel trims Bank to bank and compare if one goes really Rich or lean. I wouldn't worry about map sensor stuff because it is only affecting one side.

Valley996TT

I replaced the OEM spark plugs with these: Bosch Platinum Plus FR7KPP33U+

I really don't think it's the spark plugs. Otherwise, cylinders 7-12 should be producing misfires. The misfires are only to cylinders 1-6, and only during WOT (wide open throttle).

Welwynnick

Sorry, those are the wrong spark plugs. Those are for naturally aspirated V12's. They have a plug gap of 1.0mm, which is too great.

The turbo engines use FR7KI332S, which have a plug gap of 0.7mm.

Lots of people get this wrong, including mechanics and retailers.

Nick

cm60k

Good info. with diagram Nick,, Thanks for sharing..

,,ZAYED,,

biker349

nick, i ordered these plugs as well Bosch Platinum Plus FR7KPP33U+ . checked all the online places and even called bosch and they all said that these were the correct plugs. i bought them about a year ago and haven't installed them yet. are you sure they are absolutely the wrong plug? if i correct the gap will they work?
thanks
p.s. great info,but this is really a bummer.
if these can only be used on the naturally aspirated engines is there anybody who would like to buy my set of 24 unused and still boxed plugs?

Welwynnick

Yes, they're definitely the wrong plugs. I found out the hard way, and did a lot of research. I fitted FR7KPP33U+ to my car and it misfired. I fitted FR7KI332S and the misfire went away.

That's not to say that fitting FR7KPP33U+ will definitely cause a misfire, or that fitting FR7KI332S will definitely make it go away, but it's a pretty worthwhile bet IMHO.

Unfortunately some of Bosch's own websites recommend the FR7KPP33U+ for the V12TT, hence the confusion. However, this one at least does point to the FR7KI332S

https://au.bosch-automotive-shop.com...keyNumber=3770

Mercedes manuals always specify NGK IFR 6Q-G with a gap of 0.7mm / 0.028", while the unblown engines all have plugs with 1.0mm gap. The FR7KPP33U+ has a pre-set gap of 1.0mm, and the FR7KI332S is 0.7mm.

Bosch also state that you shouldn't re-gap these plugs, as it weakens the electrodes, and it changes the geometry of the electrodes, which affects their life.

Regards, Nick

biker349

just spoke to bosch rep. he said that both the naturally aspirated and turbo charged engines use the same plugs FR7KPP33U+. he said that is the only plug listed for all v12 engines. nick, any input?
on a side note how do you set the i think it's called dyno mode where you can see your battery voltage, battery charging, etc. on the instrument cluster. i can't find the info although i've done it in the past. i believe it has something to do with settings on the climate control. any help is greatly appreciated. i hate it when i forget things and can't find the info.
thanks

Welwynnick

The Bosch rep is wrong.

Nick


Edit: Sorry if that seems a bit abrupt or arrogant, but for those who don't know me, this is what I've done with my silver V12TT over the last four years. The items in bold are my own new modifications or service / repair methods:

Engine:
Rebuilt turbos with engine in situ
Engine mounts in situ
Long coil pack heat shields
Synchronised waste-gates
Diverter valves
T-bolt clamps
Engine radiator
Engine fan
Coil pack

Transmission:
Transmission rebuild
Torque converter
Conductor plate
TCM Connector
Oil, filter & gasket
Transmission mount

Suspension:
Wide front wheels & tyres
Compression jointed ABC hoses
Fire sleeved ABC hoses
Uprated front strut bushes
Uprated steering bushes
Rear struts
ABC pump
ABC pipes
ABC accumulator
ABC Height sensor

Charge cooling:
Engine radiator
Engine cooling pump
Custom pump controller
Coolant temp sensor
Header tank
Charge Cooler Bleeders
Insulated Charge Coolers
Insulated IC pipes

Consumables:
Front tyres
Front discs
Front pads
Rear tyres
Rear pads
Rear shoes
Battery
Spark plugs
Speed sensors
Lambda sensors
Temperature sensors
Pressure sensor
Rain sensor
Lots & lots of O-rings
Windscreen seal
Raised rear seat cushion

To-do List:
Intake pipe heat shields
ABC water cooling
Large throttle body gasket
Android Head Unit
Fuel pump
Ignition switch
Rear discs

Dr Matt

To get into dyno mode, turn the key to position 1 (ACC) then press and release the reset button three times. This should take you into the dignostics menu on the dash and you select dyno mode from there using the steering wheel buttons.

Welwynnick

https://www.ngk.com/product.aspx?zpid=9795

NGK 5648 IFR6Q-G Laser Iridium Plug
https://au.bosch-automotive-shop.com...ils/0242236571

biker349

thanks matt. i needed that. nick, i totally respect your knowledge and trust your experience. every place i check so far 5 parts places and bosch rep list the fr7kp33u+ interchangeable with the ngk. i believe you and would like to sell my 24 bosch unused still boxed plugs so i have no controversy when i do change my plugs. anyone interested?

Valley996TT

I might have to consider replacing my spark plugs with the FR7KI332S plugs mentioned by Welwynnick. But, if the plugs are wrong, why would just my passenger side bank, cylinders 1-6, be misfiring?

Anyway, at this point, this may be the least expensive thing to try in order to get the misfires to stop.

AMG-Driver

The topic Spark-Plugs for the M275 has caused a lot of confusion here over the years.

I would highly recommend to ONLY use the NGK-Spark-Plugs recommended by MB.

So you will have no trouble and even better you can say -it is not the spark Plug- if you have some misfiring (normal mileage of the plugs assumed).

biker349

valley996tt, how are things progressing. bosch has a satisfaction guarantee on spark plugs and will pay you the cost of the installed plugs, or send you new plugs. go to their website and you should find it, or google bosch spark plug satisfaction guarantee. i've been in contact with bosch and they are changing the designation of their spark plugs. the fr7kpp33u+ will now be designated for only naturally aspirated cars and the fr7ki332s will be designated for the turbo and super charged cars. a BIG shout out to nick for bringing this to our attention and bosch for responding to my e-mail and confirming the above change of classification. hope this helps everyone in the future. again thank you nick great info.

Welwynnick

I'm not really a everything-is-black-or-white kind of guy, so I was beginning to wonder if I had stuck my head out too far there.

That's a great result, and I hope it saves a few V12TT coil packs in future.

Well done,

Nick

COOPERDB

`



Interesting

Has the cause of the cylinder scoring

been determined


Thank-You
D.B.


`

Valley996TT

Biker349, thanks for providing me with this information. I have been really busy at work for the last couple of weeks (I'm a trial attorney preparing for an upcoming trial), but I will be contacting Bosch in order to get the correct plugs. Since I have already changed the plugs once, and replaced the coils on another occasion, changing the plugs again should go faster. Thanks again for this information. BTW, I haven't gone WOT on the car since the last time I did because of the misfiring. I'm going to change the plugs and then go WOT to see if that helps. I'm also going to get whatever tool I need to check the back pressure for a clogged catalytic converter on the passenger side. Wish me luck!

Valley996TT

I wanted to update everyone about the misfiring issue I had with my CL65. I changed the plugs to the NGK 5648 IFR6Q-G Laser Iridium plugs and what do you know.....the misfiring at cylinders 1 thru 6 (the entire passenger side of the engine) stopped at WOT! I'm sooooo happy this fixed the problem. A special thanks to Biker349 and Welwynnek for providing excellent information on the Bosch plugs and convincing me to take another look at the plugs. Thanks guys! So, if you are having a misfiring problem, make sure you use the CORRECT plugs. Otherwise, you will start spending money on parts that are not the problem like I did when I bought a new voltage transformer that I didn't need!