Aside from the common coil pack and spark plugs, is there anything else that could commonly cause a misfire on these?

 

The spark plug controller.

 

My guess would be a coil pack. If yours is an older S600 with the original coil packs or has coil packs with the old part numbers, that is is likely what is causing the misfire. The new part number is supposed to last a lot longer than the originals. Be sure to change out the spark plugs while your at it since it will be cheap with everything already out of the way.

 

He said spark plugs were replaced on one bank, but not the other. And one side coil pack was replaced. I'm assuming that is where the issue is, but I just wanted to know if there was anything else that I should be looking at as well while we are in there.

It's an 05. Just put a deposit on it an hour ago. Haven't picked it up yet.

 

The ignition system is painfully complicated on these. It may be possible to determine the source of the issue based on the circumstances during which, and results of it acting up. Basically how it works is the pack in the center supplies 180V coil primary voltage to each bank for the spark, as well as a 23V current for the ion current sensing feature. The spark plug fires, and then it switches to the 23V supply (which generates around 1000v @ the spark plug gap) and measures the current flowing across the ions left in the gap to determine cylinder pressure. On the s600s, it appears to only be used for misfire detection, and not for knock sensing (although it has that capability). If there is an overload/short/fault in the 180V primary voltage, there will be a misfire. If there is a problem with the 23V side of things, the computer will potentially just *think* there is a misfire, and shut down that injector as a result.

Misfires caused by an overload or short in the ignition power pack output (voltage transformer, power supply, boost converter, whatever you want to call it in the middle of the bay between the two banks), will result in that output shutting down until the ignition is cycled. This will result in you losing an entire bank until you restart the car. It will run fairly smoothly when this happens, just be WAY down on power. Interestingly enough, this scenario can be caused by a fault in one of the coil assemblies, not the voltage transformer itself. When I replaced my first coil assembly, this was what was happening on my car...I ended up having 3 dead coil sticks on that bank, and that was causing the transformer to shut down supply voltage to the whole bank.

Otherwise, more along the lines of a random/multiple misfire that could occur from worn plugs or coils sticks going bad, the same thing happens...after a certain number of misfires the computer will shut down the fuel injectors to those cylinders until the ignition is cycled, but they won't necessarily be the same bank. This is what is currently going on with my car and I haven't messed with it enough to figure out the exact cause yet...but I do know that I'm due for replacing the other coil assembly so that is probably where I'm going to start (IF the power supply to both coils checks out with a scope).

If the current owner has only replaced one side worth of plugs/coils then that is most likely your issue, though especially if it's getting up in that 70-100k+ range as far as miles.

 

Hi, as ZephTheChef stated it's the most complex ignition system in the industry (so far as to what I've seen). Any slight problem can upset the system.
Is it happening on any one particular cylinder or random? A random mis could potentially also be an air mass meter.
If it keeps missing on one cylinder no mater what I had one poor unfortunate customers CL600 with slightly low compression on one cylinder.
How this happened I'm not sure as the vehicle had a good service record.

Also just regarding spark plugs and coils in general, aside from heat doing damage running unloaded or incorrectly loaded coils, ie no plug, damaged plug, or big spark gap (more than 1/2" for testing) can do damage to the secondary windings in the coil over time.

With no load or incorrect load the secondary voltage rises above what the lacquer insulation on coil wires can stand and it eventually punches holes between adjacent windings causing a weak spark or no spark situation. Typical coil wires are thinner than your hair for comparison.

On the V12's changing coil packs and plugs at the same time is a no brainier as your brand new (expensive) pack could be damaged only after a short time with out doing plugs.

Cheers.

 

Looks like spark plugs, coil packs and the voltage transformer have been sufficiently discussed. The other most two common issues are vacuum leaks or the MAF. They all throw the same codes. There is a small vacuum block about 8 inches in front of the voltage transformer. Besides the typically looking black rubber vacuum lines there is a "harder" plastic line. It's only about 1/8" diameter and these can get brittle and break. Gently check it by feeling for breaks. Also, at the back of the engine, behind the throttle body there is another vacuum block. If any of those lines are disconnected you'll show misfires............ A faulty MAF will throw P03xxx codes and I see this as the problem about 10% of the time. If all fails check out my website V12icpack.com I rent voltage transformers and coil packs so you can test for the actual failed component. If you're going to drop $700+ you might as well buy what you need. If you get the problem fixed with the rental unit you can purchase it and return yours as a core. If you're emotionally attached to your coil pack(s) I can rebuild them for $699 each in a matter of days. Other satisfied customers on this site.....

 

This is a 2005 we're talking about. It got posted in the wrong subforum. No MAF. Did the w221 V12s go to a MAF sensor setup? Or did you mean MAP sensor?

 

Yea, I just realized I posted in the wrong forum.

That's what I get for posting while mobile!

Sorry!