Hi all,

My 2001 E55 has run beautifully until last week. 135K miles, well maintained. I drove it one day last week, zero problems, parked it, but now seemingly out of nowhere upon startup:

* Runs super rough as if only firing 5-6 cylinders. Nearly dies, surges, sputters.
* After high idle (8-10 seconds), it eventually stalls.
* Only slightly responsive to throttle input
* Fairly heavy white smoke
* BAS and ASR lights are lit (they weren't lit before)

I doubt it's a fouled plug or even a few of them (it has 2 per cylinder), or a faulty coil pack. Runs too poorly to be isolated to ignition for only 1 cylinder. Also doesn't seem like a fuel starvation, but I haven't tested fuel pressure.

The battery was old, so I replaced it on suspicion. No improvement. Put the new battery on a trickle charger for a day. Still no improvement.

I have a very basic scanner, and it shows no codes. So, I bought a new supposedly decent scanner - an iCarsoft MB v2.0 with the 38-pin adapter. It also shows no codes.

Not sure where to go with this. I could start pulling plugs and whatnot, but thought I'd post this first. Any suggestions are much appreciated!

Get a fuel pressure gauge on it ASAP. Assuming good pressure I'd want to know what the MAF is doing. An hr diagnosis at a competent MB shop will be cheaper than most parts the internet will tell you to throw at it.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

sounds like stuck injector, or leaking injector

Thanks for the tips. I'll start with a fuel pressure check.

How long was it sitting? Maybe mice chewed through some things...

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

The MAF on my '01 E55 has gone out twice in 95K with similar symptoms. My crappy code reader couldn't find a code, but an autoparts store reader did find the MAF code ( their reader - they read your codes for free).

Check for the Bosch part # for the MAF, much cheaper than the Mercedes and identical. FCP site has them cheap with a lifetime warranty.

Good luck, the E55's are great cars.

Chuck

It only sat for a week. Fuel pressure test showed constant 48 psi / 3.3 bar for a few minutes.

I checked resistance of the injectors; each showed 14.4 ohms. It won't run long or well enough to listen to each one for clicking.

Good tip about the MAF sensor. Never been replaced as far as I know. I'd have to tow it to a parts store or dealer to diagnose, so I may replace the MAF just to rule that out.

To wrap this up, turns out it was indeed the MAF sensor. Starts and idles smoothly after I replaced it.

Thanks so much!!

Kent, glad to hear you got things sorted out. When was the fuel filter last replaced?

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Fred Hoelzle

Thanks Fred. Fuel filter hasn't been replaced to my knowledge. That was the cause of a hard start problem on my 400e several years ago, so good idea - I'll pick one up!