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David C Klasse 02-19-2014 05:41 AM

2003 E320 Acceleration Woes...
So I've got 208k miles on my W211 with the M112.949 motor. Plugs, and plug wires, fuel pump, filter & sender, engine air filters, high-quality fuel system cleaners (ie Techron, & another great one, i forget name) have either been changed or used in the relatively near past.

So here we go: upon quick throttle, usually from a stop, the engine totally cuts out/bogs for a moment or two (doesn't seem like a misfire), and if I keep the gas on, probably to the floor, the engine suddenly & seemlessly revs up properly like the powerhouse studly motor that it is.

So, the problem is often intermittent, and has occasionally stalled while at a stop or idle or switching between fwd & reverse gears.


I'd like to know if it could be the throttle body, or maybe MAF or other sensor or WHAT could be causing this? It is progressively getting worse. It seems to me as if it were the throttle "motor" sticking in the housing... but I could be way off base.

I have no MIL (check engine) light on FWIW.

What gives???

Can't Know 02-19-2014 05:48 AM

The lack of a MIL/CEL isn't conclusive, because codes can store before the algorithm reaches the point that it triggers the MIL.

Bottom line: The first step with a drivability issue is to check for codes.

You're in CA, so you can't just run by an auto parts store, but you can order a basic stand-alone code reader from amazon for under $20. It will read and clear OBD-II codes, which in many cases is all you need. Autel MaxiScan MS300 CAN Diagnostic Scan Tool for OBDII Vehicles: Automotive

Until you read codes, you'll still be wandering around in a cave without a flashlight. ;)

Good luck.

David C Klasse 02-19-2014 05:57 AM

THe good news is that I ordered a OBDII wire (to USB) with appropriate software... it's been a long time in the waiting... but I finally did. But until it arrives, I will have ALex (my local mechanic) get a me a reading of the codes.
Thanks for stating the obvious (sometimes I just need a SLIGHT nudge)!

oldsinner111 02-19-2014 01:11 PM

check all sensor connections before spending money.I replaced $710 in parts only to find my crank sensor wire had come unplugged tight.I had run over debris on the road.

pawoSD 02-19-2014 02:01 PM

Almost sounds like a sensor issue or perhaps wear and tear on the drive by wire throttle pedal sender unit...if it has a dead spot near the beginning of travel it might be causing a signal hiccup.

David C Klasse 02-19-2014 04:03 PM


Originally Posted by pawoSD (Post 3289489)
Almost sounds like a sensor issue or perhaps wear and tear on the drive by wire throttle pedal sender unit...if it has a dead spot near the beginning of travel it might be causing a signal hiccup.

This is kind of what I was thinking... is there a particular part number? The throttle body housing? THey can't be cleaned on the newer cars, I've heard... Do you think it could be the MAF?

Thanks for the timely responses!

Hirnbeiss 02-20-2014 06:57 AM

Yes, could be MAF, crank sensor, TPS ...

David C Klasse 02-20-2014 07:30 AM

Crank shaft position sensor was replaced a little over a year ago.

Can't I clean the MAF (very carefully) myself? As opposed to purchasing a new one...

What is the TPS an acronym for?

Ferdman 02-20-2014 07:48 AM

David, as far as I know a bad MAF sensor would activate the Check Engine light. At least that was my experience with our 1998 E320.

Hirnbeiss 02-20-2014 09:02 AM

TPS = throttle position sensor. Let me google that for you

Doktor Bert 02-20-2014 10:57 AM

I would check the TPS....X2

David C Klasse 02-20-2014 05:37 PM

X 2? As in yes YES check this part first?! I gather.

I don't really know how to "check" it - not too terribly savvy (or confident) checking voltages, etc...

I think I just need a really good, honest, independent mechanic that is very familiar with Mercedes-Benz, more specifically the 112 motor....!?

David C Klasse 02-20-2014 05:59 PM

MAP = TPS ??
Is the MAP (Mass Airflow ? P=? <--just a guess) synomous with TPS?

Hirnbeiss 02-21-2014 08:14 AM

No, the TPS is just the electrical connection between your foot and the throttle plate, converting mechanical movement to an electrical signal. MAP stands for manifold air pressure, and I think on your model it is integral to the MAF, which measure the real amount of air being sucked into the engine, since that varies with temp and pressure.

David C Klasse 02-21-2014 08:24 AM

THanks... I am pretty sure that the MAF failure would definitely illuminate the MIL... so given the the MAF is still good....
Do you think the changing the TPS is a good starting point? Or should I have it checked first? I have definitely given this car a good run for it's money since I bought it outright in late 2006 with 47k miles on it (a least trade in).
Might it be a good idea anyway?

Thanks... I need all the help I can get.

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