I recently had encountered a very rough running engine after hard acceleration (high RPM), until the key was cycled, and then the engine would be smooth again.
SEE POST: http://www.peachparts.com/shopforum/showthread.php?threadid=27884

Well I took the car to dealer for diagnosis... 3 days later, and 3 rental cars later, I got the belt tensioner SHOCK and BELT replaced for all of $70. I told them to change the shock along with diagnosing the problem. ANyway, they changed the belt without my approval, so I got it for basically free!
Anyway, they didn't get around to putting the car on the DINO to get a real good look at the rough running problem. Geez, they didn't even pull any codes!! But they suspect that the wiring harness would be a likely culprit. I guess it's never been replaced on my car, and I asked the service advisor to show me some of the wires... he did, and they didn't look too bad at all, even with squeezing them? I assume it's bad enough, since no wiring harness replacement showed up on the Vehicle Master Inquiry. I discussed with my service advisor the MB GOodwill policy. He said that Mercedes usually picked up ATLEAST 1/2 the cost. He said they even once picked up almost the entire cost for a 94 E320 with 118k miles. So that looks good.

Now I have a very quiet engine with the belt tensioner shock replaced (and BELT.... free ), but if you push it, I will get an extremely rough running engine (though doesn't feel as though it's going to stall, in the least. Runs like crap, but RUNS. I leave for Mammoth on Sunday... so lets hope the beauty holds out for my 375 mile trip each way! I guess I won't be doing too much passing (low RPMs!), a good thing I'm sure.

Ok my question: I have 110,000 miles on my car now... is it possible that the plug wires could be causing the misfire, which in turn, switches off the injectors? If it were the plug wires, wouldn't I have a rough idle most of the time? Does my problem seem like it's probably some random whatever wiring harness problem? Or is there anything else (could be in congruence with...) that might cause this? (car runs smooth once engine is turned off and then fired back up)

(First rental car was a Nissan Maxima... broke down on the fwy with 180 miles on it! Got a CE light and AT CHECK light! Called Enterprise, and they brought me a GMC Safari... what junk! So I went back to Fletcher Jones and got a BUICK Park Ave with leather, Auto Climate Control... WOW, what an interesting vehicle to have for a couple of days!!)

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)