DNewton

My 2008 SL600 just went off warranty, not one warranty item in 4 years, then on Sunday it starts to misfire at a stop light and dies. Was able to re-start and get it off the road before it died again. Second re-start I was able to get home about 500 yards, "Lucky". Pulled up to the garage, died again. Third re-start was able to pull into the garage. The car starts fine and runs for a couple of minutes at idle then misfires and dies. My friend and neighbor came over with a code reader: PO 301, PO 302, PO 307, PO 311, PO 309, PO 312, PO 308 all misfires. In doing some research on this site it looks most likely to be coil packs. Does anyone have any experience with MB's warranty? The car has 20,000 miles and the warranty expired about 40 days ago. Any other recommendations other than coil packs?

Thanks Dan

Benz-O-Rama

Yep, sounds like coil packs. Since you're barely out of warranty, haven't made a claim in 4 years, and the car only has 20K miles on it, I'd suggest talking to the service manager about them extending you a goodwill repair. Those packs are pretty expensive, BTW...

mkhurley

Your showing both coil packs, before doing them I'd go with the ignition module, they have it in common. It sits on top of the engine, center, remove the covers, it'll be obvious. 20K is early for the coil packs, specially both at once. If your gonna keep it, get an extended warranty, you'll be happy you did.

DNewton

Thanks mk, I looked into the extended warranty and the $3,800.00 made me think; no trouble in 4 years; the warranty only extended coverage for I think two more years; I figured I wouldn't spend that much on a pretty much trouble free car. Well here we are, 20/20 hindsight, looks like I may spend $3,500 right out of the gate.

DNewton

So it's fathers day and I had put about a gallon and a half of fresh fuel in the car from my lawnmower can back on the 11th while we were reading the codes. So I pushed on the connectors on the main computer and each coil pack, nothing seemed loose. Started it up this morning and let it run, no misfire, ran smooth. Let it warm up to operating temperature, all good. Drove to the gas station about 2 miles filled up with fuel. Drove home and pushed it several times ran great. Pulled it into the garage in a confused state of mind.

Is it possible I have some bad fuel in the tank from my last fill up, when the tank was low it caused the problem? When I put in the fuel from the gas can it floated the bad fuel up away from the intake once it settled; or, is this a temperature related issue and the vehicle needs to be run for an extended period to reproduce the problem? I'm a little hesitant to drive too far away from home for fear of having it break down in a really inconvenient spot.

Wolfman

Unless you have a terrible dealer, any service adviser will get this covered under goodwill by MBNA.

It could be be bad fuel though, too...

DNewton

Since my last post I have now driven the car about 150 miles including one trip in 90 deg weather, hard to believe but it hit 90 Deg. F. here in Western Washington, set a new record. Back to the misfire issue; the car is running great and has not had a repeat of the misfires; we have reset the codes. I sure hope it is related to fuel quality, if not; I have an intermittent electric/electronic issue and the will be a pain. I will keep everyone posted with changes; I am going to change the fuel filter and hope it was bad fuel. Thanks to everyone for your comments.

Dan

DNewton

I have taken the car on two long drives since my last update; one drive of 400 miles in 100 Deg. F. weather and another drive of 300 miles in 90 Deg. F. weather. I have had no further issues with misfire. Just wanted to keep everyone in the loop, looking like it was bad fuel.

DNewton

It has been over two years since this began. I do believe I have resolved the issue. The fuel gauge is off, this car runs out of fuel with the gauge reading 1/8th of a tank. I can get the condition to repeat if I let the fuel level drop below the 1/8th of a tank level, put fuel in and issue is gone. I was concerned with a weak fuel pump; so I ran the car under a heavy acceleration load with just a 1/4 tank of fuel no issue with any misfire. I really think the fuel gauge is just off and the car is running out of fuel with an 1/8th of a tank on the gauge.

Does anyone have any additional ideas?

kbob999

Replace the fuel sender / tank float. Used about $60 on eBay.
Need to pull the center trunk carpet panel, it's below the rear window.
Build a tool from 2 bolts and a stick of wood to turn it 1/8 counterclockwise. Pops right off.

Do you have a clanking from the tank when half full? If so, this would be a good time to address the fuel tank baffle issue. Not sure what years were affected, but the early one had it.

Lucky is was not coils. You dodged a bullet.