Irregular misfire
Thread Starter
Junior Member
Joined: Mar 2015
Posts: 28
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07 S600 (W221)
Irregular misfire
MBWORLD
Check engine light came on in 07 S600, code was diagnosed with P0300, P0306 and P0311. Because these were on separate banks, I 'thought' it was a plug issue, plugs were replaced, codes cleared, but after about 15min (or 50mi), check engine light returned with same codes. Because each plug is in a different ignition coil pack, is there a way to verify that the coil pack is the issue? I really don't want to replace both coil packs if its not necessary.
Thanks
Check engine light came on in 07 S600, code was diagnosed with P0300, P0306 and P0311. Because these were on separate banks, I 'thought' it was a plug issue, plugs were replaced, codes cleared, but after about 15min (or 50mi), check engine light returned with same codes. Because each plug is in a different ignition coil pack, is there a way to verify that the coil pack is the issue? I really don't want to replace both coil packs if its not necessary.
Thanks
MBWorld Fanatic!
Joined: May 2015
Posts: 4,037
Likes: 1,012
From: Miami, FL
2003 CL 600
6 and 11 are both rear cylinders, I'd suspect a vacuum leak or fuel pressure problem. Look at the actual value data for them and see if anything is amiss. It's highly unlikely that both coils die at the same exact time and only on 1 rear cylinder. Does the car have a noticeable misfire?
Thread Starter
Junior Member
Joined: Mar 2015
Posts: 28
Likes: 0
07 S600 (W221)
Thanks ItalianJoe1
Yes, I do notice it does run a little rough with lack of power and responsiveness. What value data are you referring? I should say, the codes came from AutoZone, I currently don't have a STAR unit. How do I check for vacuum leak or fuel pressure issue?
Yes, I do notice it does run a little rough with lack of power and responsiveness. What value data are you referring? I should say, the codes came from AutoZone, I currently don't have a STAR unit. How do I check for vacuum leak or fuel pressure issue?
MBWorld Fanatic!
Joined: May 2015
Posts: 4,037
Likes: 1,012
From: Miami, FL
2003 CL 600
Don't waste your time with generic OBD2 scanners. Get the car diagnosed by a competent MB tech or independent that knows those cars. The diagnostic info presented in SDS will show what is misfiring and why. The parts are too expensive to play a guessing game on these cars. If a diagnostic cost you $300 but saves you from spending $3k on a pair of coils, seems worth it right?
