Hi Guys:

I took my 2007 S600 (with about 68K miles) on a short 100 mile round trip and, when almost home and having just filled up with gas, I got an Engine light (CEL) and noticeable loss of power. When I got home, I could smell unburned gasoline and knew something was not right. The only thing unusual about the journey was, I drove at about 75 mph in really heavy rain— probably shouldn't do that. However, that was about 2 hours before the CEL occurred.

When I got home, I let the car sit for a couple of hours and hooked up the STAR diagnostic. As suspected, P0300 and cylinders 1-6 misfires (pass side). I could still smell unburned fuel as well.

I’ve replaced my left side coil pack a couple of years ago, see, https://mbworld.org/forums/s-class-w...placement.html

So, I was guessing either right side coil pack (CP), or the voltage transformer (VT, not replaced) that sits in the middle of the engine and provides power to both right and left coil packs. Being evening, I didn't care to delve too deep into it, but decided to do one check. I removed the 18 pin (or whatever) connection to the right side coil pack and checked for ground. All okay. I snapped the connection back in and cleared the fault codes.

Voila, when started, no CEL and no unburned gas smell. I did a short test drive and had full power, no CEL and no codes...

Can it be that easy???

Or, am I looking at an intermittent problem. New fuel fill up? Heavy rain (no moisture seen anywhere)? I’ve had a Ferrari that would continually throw CEL's and cured it with a little WD-40 sprayed in connectors. I didn’t even do that here... Just unplugged and reconnected…

Unlike my last coil replacement, with random misfires, this was a whole bank of cylinders shutting down. But, it seems weird that there could be a complete shutdown followed by a full recovery???

Just wondering if anyone else has had a similar experience. A coil pack doing a few misfires is one thing. A full bank shutdown is another... You can’t drive any distance like that…

I don’t want to be worried about taking a trip of any distance and wondering if CP or VT is bad… The VT can be changed in about 15 minutes, not so the CP. And, they’re about a Grand a piece, so it’s not like my Jag XJ-8 that I carry an extra $17 CP in the trunk, just in case…

Any input or comments welcome….

Thanks…. Mark on South Padre Island

 

The only issue I see with driving 75 in heavy rain is the potential for hydroplaning. Any passenger car should be able to do that without mechanical troubles. It's normal road conditions.

Connectors -- I speak from the standpoint of 20 years or so of maintaining and repairing midrange and mainframe computers, plus a lot more years maintaining a lot of other gear. Connector pins can oxidize. Moisture, oil, and other contaminants can make their way into connectors and cause intermittent problems. Sometimes they need to be cleaned with a burnishing blade, spray degreaser or my favorite -- a pink eraser. But, a lot of the time just the wiping action of un-seating and re-seating the connector is enough to "fix" the problem, either temporarily or permanently. I'm not saying that was your problem, but I am saying it could have been. So could some water or other contaminants in the gas. Since you say you had just filled up, I'd put that close to the top of the list of suspects.

 

Thanks Dale, I immediately thought “bad gas” before I hooked up Xentry. The exhaust smelled kind of like varnish—which I now guess is what unburned fuel smells like after going through the cat….

But, I had exactly 7 codes. One P0300—random misfire—and all six right-bank cylinders misfiring. I can’t see bad gas doing that.

And the rain… I'm with you. Correlation was too remote... And, I've done that before, and worse...

For good measure, today, I again removed the CP connection and the VT connection (which, BTW, are the same type of connection) and sprayed them with electronic cleaner followed by WD-40. Did another test drive and all is well. The connections were very clean and I saw no signs of corrosion...

Man, I hope it was “just” the contacts. My concern is it’s the VT, which works fine until just the right amount of heat sink causes it to fail to send voltage to one bank… Has anyone had that kind of problem???

I have. My Jag had a bad CP that only misfired if driven over 1 hour at speed when it was over 90F outside temp. A condition that was only duplicated twice over a 5 year period.

Luckily, I have a 75 mph speed limit within about 10 miles of me and I can seriously argue with the speed limit for about 20 miles. Living close to the latitude of the Tropic of Cancer, it won't be hard to find a 100F day for an endurance test and not be too far from home to limp home.

Final question: Can the ECU 2.7.2 shut down a whole bank of cylinders that would require a dealer/Xentry reset? And, why? I didn't get a flashing CEL but, IIRC, Xentry said I should have...

Regards.... Mark

 

Not really. If it smells like varnish, it's BAD gas. Really bad.

What is this "speed limit" thing of which you speak? Interstate speed limit in NE is still 75. There was an effort to bump it up to 80, but it didn't pass. Of course people routinely cruise at 80 anyway, it's a big state. I don't routinely drive at felonious speeds, but I would not rule out having occasionally exceeded the posted speed once or twice. One does have to road test things occasionally, you know.

 

Hmm, My brain jumped to coil pack insulators. I'm glad it was just the connector.

I use this stuff called Deoxit D5. It's in a spray can and it's kind of expensive but it does a great job cleaning and protecting connectors, terminals, grounds, all that stuff. I can even spray it directly into switches, sliders and potentiometers and it fixes them right up.

 

Thanks Guys:

Dale, the posted speed limit in TX is advisory... Meaning you are presumed to be going too fast for conditions if you exceed it… But don’t try this at home kids… Driving one of the fastest, safest sedans in the world over the limit won’t get you very far when arguing with a TX state trooper…

Shadly, I haven't heard of that stuff but will heed your recommendation. You probably are familiar with what I used, CRC Electronic Cleaner, which is on the shelves everywhere. Just a simple way to blow out unwanted crap… of which I didn’t see any…

But, to clarify, although the Fed mandated OBDII codes—even on Xentry-- call it a "misfire", and "random"... these were not random misfires. Best I can tell, I lost “fire” to all six right cylinders at once. The left bank was totally unaffected.

I’ve dealt with a failing coil pack (CP) before and that gives you random misfires, (at least it did in my case). As I understand it, the V-12 has left and right, wholly self-contained, coil packs. But, they can't be powered by 12V DC, so there’s a single Transformer (VT), that raises the voltage for both CP’s. And, it sits smack-damn in the middle of the absolutely Hottest part of the engine. But, the VT, although in one box, uses totally independent circuits for left and right CP's. So, the VT fails either left or right, but not both L&R. CP’s, on the other hand, fail independently. And, I won’t take credit for it but came to the same conclusion as Rupp Clark with v12icpack.com, IT’S FLIP A COIN whether the CP or VT is bad when you lose one cylinder bank, like I did. And, even Xenrty won't tell you which it is...

My dilemma is, everything, CP and VT, came back to full functionality. Was it the connection??? Seems to be… Just fishing if anyone has had a similar experience and for the thoughts y'all have sent so far. Specifically, I'm wondering if a total CP or VT failure can come and go??? And, is it related to heat sink??? My research on the VT reveals it’s full of low quality capacitors that can leak or fail. But, just my experience, they don't usually come and go... Generally, it's just kaput!

Finally, and in commentary, when I first started posting here, I complained that it was more about which car wax to use (not that that is a bad thing) and a lack of “how to fix” sharing. As our vehicles get older, that is changing. More and more of us are interested in “can I fix this?” I’ve been using the collective experience of Forums for years to fix various cars; Infinity, Mazda, Jaguar, Porsche, Ferrari… and, usually, sometimes with a bit of nasty criticism, got the answers I needed. Just saying, this is a great forum and, hope the mystic and pretense of MB doesn’t slow it down. They are just cars, albeit the S class is about as complex as they get… at least in today’s state of affairs and technology...

As usual, with Regards… Mark

 

The fastest sustained run I have ever made was in TX, back in the 90s when the speed limit was still 55. Houston to Ft. Worth in a rental car. I have no idea how fast we were going, me and the half dozen other cars. The speedo needle was buried so deep I thought it would bend. We maintained that speed for a good 3-plus hours before it got dark and enough of the others dropped off at exits that I figured I ought to slow down to 75 or so. Good times. I've gone faster, but never sustained for that long.

As for these cars... it's the wrong day to ask me about that, so I'll shut up and let you enjoy your success.

 

Dale, I suppose it was success. Just to follow up… I took the car on a high speed run today, with numerous short stops just to make sure the car got a full dose of heat sink. Essentially, duplicating or exceeding the conditions, as they existed, when I lost the entire right back of cylinders as described in post #1… Including, an extended run at about 2500-3000 rpm in top gear (at 3000 rpm, that’s 300 sprays of fuel and 600 sparks PER SECOND—A little V-12 trivia).

Anyway, no misfires. About 1/4 tank of premium gone but peace of mind-- sort of. To reiterate, the cure seemed to be disconnecting and reconnect the plug shown in post #1. As stated... can it really be that easy???

Regards… Mark

 

In my experience... yes, it can be. It's not usually, but I've seen it before.