Below is a link to my (well a friends) misfire problem. I should have put misfires in the thread title,maybe a mod could add it. The "get on it " symptoms you mention sound familiar, These misfires hovever were confined to bank 2, but still it's food for thought.
Are you able to get your fuel trim figures?
https://www.crossfireforum.org/forum...tml#post892341

 

I have had this issue for about 6 or 7 months and thought I had it figured out, but it came back. I have replaced everything you guys mentioned it could possibly be and it has not fixed the problem. Fuel pressure is fine- new fuel pump, fuel injectors, plugs, wires, coil packs, Cam positions sensor, crank position sensor, crank pulley, temp coolant sensor. Fuel pressure test, vaccum test, compression test all to no avail. Which leads me to believe it's in the exhaust system. Either the cats or the o2s. Could be back pressure from the cats, I did run across a thread on the MBworld forum that said it was his intake manifold. I have not had time to change the cats or the o2s, but I plan on it in the near future as well as change the intake manifold. I can say this has turned into a hobby, but I don't mind. Anyway, happy hunting. If I figure it out, I will post an update. We might need to compare cars to see if we can find a common factor that might be causing the issue. Oh, BTW mines now has 406,000 miles.

 

Hi liljay, Thanks for your post. I think you win the trophy for the highest mileage Crossfire still operating on this planet! I have cat delete downpipes (from Needswings) and the car only has about 60,000 miles. I've had this issue intermittently before but now it's happening almost every time I tromp on the pedal to "make it go fast". Please post here if you discover the problem . . .

Hi TommyLT, Thanks for your post. I looked at the posts in that link. Nothing popped out at me that might be helpful.

Hi Padgett, Thanks for your post. I have an INNOVA 1360b ScanTool w/ABS-SRS. I need to pull out the instruction manual because I believe it is able to read the deeper codes too. When I got the P0300 code it showed it was 1 of 3 trouble codes but I couldn't seem to get it to display the other codes. You know the saying, "When all else fails, read the instructions!" DUH . . .

I'll be taking a fresh look at things tomorrow. Now that I think about it, it does act like a fuel issue rather than an ignition issue. I'll post more clues (or more hopefully results) as I stumble along tomorrow . . .

 

OK - I read the owner's manual on my scan-tool and pulled up the deep codes. They are P0305 (misfire on cylinder 5) and P0306 (misfire on cylinder 6). I didn't get a chance to look into the fuel pump and fuel pressure situation. I have to go to work now so maybe I'll be able to check that out in the morning. One step at a time . . .

 

WORK ???? I though you sold all the limo's and retired

 

What type of intake do you have? If it's the original, I would change the air box seal that connects to the MAF and tighten the brackets that connect to the bearings (rubber bumpers on the valve cover). I found mine not clipping on to the rubber bumps tight. That caused the airbox to raise slightly enough for to much air to enter. I had suffered with the High RPMs for a while. Went through 4 or 5 MAFs. Each time they lasted for awhile and then high RPMs. I never thought about the seal or the airbox lifting up enough to cause to much air in the intake manifold and cause misfires. I installed a new seal on the airbox 2 days ago and it drove a lot better. Today I did an inspection and found the airbox slightly lifted off the MAF. I had suspected the rubber bumps and swapped the ones closest to the MAF to front of the engine when I installed the new seal. Today I crimped the metal brackets on the airbox that clip on the rubber bumps on the valve cover. I will test it in the morning. Follow the link below to see the clips on the air. They are item 287 in the picture. Lots of part numbers for the SLK 320 on this sight. I ordered the seal from Needswings.
https://www.ilcats.ru/mercedes/?func...=4&language=en
Part number for the seal on the airbox and rubber bearing
A1120900089 Intake airbox bearing
A1120940180 SEAL MAKE MANN & HUMMEL

I also changed the 2 seals on the MAF elbow. One at the end where the MAF connects and the one on the end where the elbow connects to the throttle body.

 

Just looked at your car. It's a SRT so not the airbox! I'm going to test mine in the morning.

 

Airbox was my issue all along.

 

liljay . . . Thanks for your posts . . . I give up. I'm taking my Crossfire up to JS BENZ (my "go to" independent repair shop) this week. When they figure it out and get it fixed, I will post what gremlin(s) they found to be causing the problem.

 

BTW there also used to be 24 cans of oil in a case but they fixed that.

 

Hello again everyone, So I picked up my SSB SRT6 roadster from J S Benz in Miami today. It is running perfectly again. As you may remember I was getting the P0300 generic "random misfire" code during WOT. Checking deeper the specific codes were P0305 (misfire on cylinder 5) and P0306 (misfire on cylinder 6). I'm not sure this will help anyone having a similar problem but here's what they did:

They replaced the coil packs on cylinders 5 & 6. That cured the misfire on cylinder 5 but we still had a misfire on cylinder 6 / but now only at peak RPM WOT pulling 4th gear (like around 120 mph). It ran perfectly through gears 1st, 2nd, and 3rd. They reduced the fuel pressure from 60 psi to 55 psi and that fixed the issue with cylinder 6 too.

I don't pretend to understand it all (that's why I took it to the experts at J S Benz) . . . just reporting what they found and what they did to "fix" the issue on my SRT6. This one runs like a race car again! I'll be taking this one to the Fall Dragon as I had originally hoped.