Hello, my s600 has the following probelm:

Sympton:
"Check Engine" Light on twice, only after driving for a long distance (hot engine), not always on, returned to normal ( Light Off) after parking overnight.
Currently, no more light on.

Diagonsis:
Brought to MB Dealer

Report:
20086 QUICK TEST-- FOUND MISFIRE CODES ON #7 CYL. CODES P0300, P0307, P20FA. UPDATED "ME" CONTROL UNIT. DEFAULT INITIALIZATION. PREFROMED CHECK AS PER TSB 07.61-413 REV 3. REMOVED LEFT BANK COILS AND SPARK PLUGS. FOUND READ SEAL ON #7 CYL IS BURNED AND PLUGS HAVE OIL ON THEM.

Recommand: REPLACE BOTH BANK COIL PACKS AND ALL SPARK PLUGS.

I paid $374.70 (plus tax) labor of diagnosis (4hrs for that report???) ! [:@]
Dealer quoted $5,000 for parts (mimimun estimate), labor & Tax extra,
plus3 weeks waiting for parts from German!!! [:-][/align]
I declined the offer and escaped.[/align]
Is it necessary to replace all parts like dealer's recommand?
Can I just replace the coil & plugs for #7 Cyl.?
If you have a solution or suggestion, please comment.
I would very appreciate it.
Thanks.[/align]

 

Hi,

QuickTest shouldn't take 4 hrs!!....reference its name.

P0300 is random cylinder misfire.
P0307 is No7 misfire.

Why is plug lead boot burned? Arcing. Why? Salt deposit / dirt maybe?
Suggest new lead.
Since issue is specific to no 7 no need to change all leads but if expense is no problem then changing aALL will ensure you don't have a repeat on 6, 5 4 3 2 1 etc. further down the road.
Buy MB OE Genuine lead. If it is NOT MB genuine then you will HAVE to change ALL but I still recommend OE GEnuine.

Coil pack should be OK, at least at this stage. (Quite expensive)

Big problem is oil on plug!!

OK. If cylinder has been down for some time due to no spark at plug tip this would explain oil BUT there could be other more ominous causes. Hope not.

Since plug is now foulded change at least No 7 with MB OE Genuine...not look alike aftermarket or otherwise you will have to change ALL plugs.

Looks like the "Quick" test + a good technician has pinpointed your problem = Ignition leak to earth on No.7

Good luck.

Stuart

 

hi, Stuart,
thank you so much for your help.
Did you suggest to replace #7 cylinder's plugs with OE genuine first?
I recalled that technician said about coil's voltage, should I concern it, too?
Is plugs replacement a DIY job? or, better to find a pro?
Thanks again & regards,

 

Hi,
Important. What did the technician say about the coil voltage?
Too high and it might have caused the arcing...unlikely.
Too low and it might cause a misfire / fouled plug which is linkedto your problem. If so it MAY need to be changed. Could try swapping with another cylinder and see what happens. Voltage is the result of the coil pack, the sparkplug and the mixture in the cylinder so the pack can be OK although the voltage is recorded as being too high or low. As the sparkplug gap increases it can cause the coil pack to increase voltage....

If plug fouled best to fit new or at least swap it out with another cyclinder and see if it returns to correct colour.
Plug change should be DIY if you have some knowledge of working on cars. Look at previous posts. Important not to overtighten and you MUST use some copper grease oir similar otherwise the plug won't come out next time around. Also need appropriate 3/8" drive socket set.

If you change just one plug...as a cost saving...ensure it is the exact same spec. i.e. get MB genuine spare not something that looks similar. They cost MUCH MORE than ones that look similar BUT you will be sure that the spec is correct.
Stuart

 

in your case you cant only replace no 7 clylider coil due to its complete pack of 6,so you ll have to at least replace on 1 BANK ITS NOT A DIY JOB OR YOU CANT GET ANY COIL PACKS FOR V12 APART FROM MB THE RIP OFFS,GOOD LUCK HOPE ALL GO WELL.............. naz

 

OK.
Wasn't aware that the V12 coil pack was per bank but I was trying to convey that it isn't necessary to always change everything in sets IF you keep to OE genuine parts.
If the whole pack has to be changed this underlines the importance of ensuring the validity of the voltage reading error on No7.

I do not have the full facts BUT I suggest that the voltage was down due to the arcing caused by the burned boot which in turn was due to insulation breakdown (age) or contamination (salt etc). Correcting the arcing WOULD LIKELY modify the voltage signature and therefore save a whole load of money.

...on the other hand you can change everything (overkill) and YES you will be more likely to hit the problem BUT at considerable expense.
This expensive (to the customer) approach is what many garages do so as to maximise their REVENUE and also improve the chance of getting the problem resolved at the first hit.

Stuart