604benz

Hi Guys I'm just in the process of buying an 07 S65, took it to my indy shop and they say mechanically all looks good, just need a pair of rear tires.
CEL was also lit and code came up as misfire in all 12 cylinders, car runs smooth and lots of power, tech guy told me it could be cheap fuel the dealership put in, any ideas, car has 80000 kms.
Thanks

AMG X

I would be skeptical that the car is as mechanically sound as they think it is.

It may be an ignition system issue, the coilpacks on the v12's are known to cause misfires. Cheap gas (I.e. poor brand, low octane) would make the timing pull back.

You should post the codes causing the CEL, maybe an experienced member can help you out better.

604benz

Can the coil packs be replaced by individual coils or only come in 12 packs.

marktan

On the M275, two coil packs (one per bank of 6 cyls...2 plugs per cyl). about $1200-$1500 each installed.
I highly doubt it is bad fuel.

MB-Dude

"Cheap gas" is probably not the culprit here, but contaminated fuel *may* be. I had a situation ~6 months ago where a tank full of gas (from a Chevron station, no less), caused the engine to die 1 block from the station after filling up. Fuel was contaminated with diesel. The codes were all misfires. Drain the tank, refill with fresh fuel, and the engine ran fine (after about 25 miles or so). The point is fuel can be contaminated enough to create misfiring but not bad enough to prevent engine operation. Is that the case here? Not a clue; not enough data. If the codes are cleared and don't come back after 1/4 tank of known good fuel, then the fuel was the problem. In fairness, I'd suspect something else that's common as I wouldn't expect all the coil packs to fail at once.
Cheers,
Jeff

jnash

Having examined the internal circuit of a coil pack I would doubt seriously if all cylinders would all misfire at once, and def not all 12 with two coil packs. Typically you would get one or a few misfires with a bad coil pack. I'm sure if the engine is now running fine and you run a quick-test on SDS that there will be no misfires on all 12 again.

georgebushca

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