Something else a faulty MAF can do !

BachelorDays

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Hi everyone,

Haven't posted for quite a while, but thought I'd share this experience since it has reached conclusion. The full story is in the reference given, but in essence, a faulty MAF on my car was causing a pending P0221 and disengaging the accelerator.

I know the MAF was fine earlier because at 84k miles (albeit 3 years ago) I had a STAR check on the car and nothing was reported on the MAF. I think a combination of a jump start and long cranks killed the MAF.

Amazing that a faulty MAF can cause this error too. Or maybe its the way the MAF gets killed - ie long cranks/ jump starting messes it up in this manner that its signals make the ECU disengage the throttle. Bizarre!

(Post No. 14)
http://www.benzworld.org/forums/w203-c-class/1694437-c320-fault-code-p203b-esp-warning-2.html
 

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Cranking or low battery cannot kill the MAF, they wear out and fail through natural causes. As the MAF is responsible for setting up the fueling, the engines will not run well if the wrong fueling info given. They do not always show up on STAR and one must read between the lines of what STAR says
 
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BachelorDays

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Cranking or low battery cannot kill the MAF, they wear out and fail through natural causes. As the MAF is responsible for setting up the fueling, the engines will not run well if the wrong fueling info given. They do not always show up on STAR and one must read between the lines of what STAR says

STAR, in this instance, was fairly clear about the MAF being faulty (in both codes and live data). What killed it will always be open for debate, but the way the fault manifested itself is unusual. Normally a MAF makes the car/idle run rough and/or stall at low engine speeds. Killing the throttle and posting P0221 is much less common - which leads me to believe that it may be related to the long cranks and jump starting.
 

alexanderfoti

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Are you sure you havent just got an intermittently faulty TPS?
 

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Cranking or low battery cannot kill the MAF, they wear out and fail through natural causes. As the MAF is responsible for setting up the fueling, the engines will not run well if the wrong fueling info given. They do not always show up on STAR and one must read between the lines of what STAR says

Many mafs get blown from jump starting. The M112/113 engines are notorious for it . The M111 I have experienced as well
 

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Odd that it has never ever come up before.
 

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Many mafs get blown from jump starting. The M112/113 engines are notorious for it . The M111 I have experienced as well

Are you referring to faulty procedures when jump starting or any jump starting? I was under impression that jump starting was not an issue if carried out correctly. Am I wrong there?
 

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Are you referring to faulty procedures when jump starting or any jump starting? I was under impression that jump starting was not an issue if carried out correctly. Am I wrong there?

You are right there, carried out correctly it is no different to the cars battery.

Jumper packs I never like, they all have spikes.
 

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A lot of people run the engine on the donor car when jump starting which is not a great Idea.

Sent from a mobile device
 
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BachelorDays

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Odd that it has never ever come up before.

That's primarily the reason I posted it. I practically took the car apart looking for the fault - well, the electronics anyway. Lucky I did that though - found the transmission TCU flooded and probably saved the transmission just in time.

I found one reference (Olly, I'm quite sure) where it was mentioned that a jump start can kill the MAF. That's what got me thinking about the MAF as a potential candidate. But the P0221 & ESP/BAS warning had me puzzled for a long time.

It was happening very regularly. Not once since changing the MAF a few weeks and 1,200 miles ago. So not an intermittent TPS. Besides, once I got it down to how it was happening I was pretty certain about the MAF. A faulty TPS would play up on kickdowns, etc too.

The two things that led me away from the actuator and the throttle body sensor were the fault never appearing during the first 15-20 minutes and it only happening when the foot was off the accelerator. The former made me think it was only happening once the car went into normal drive mode (as opposed to a cold engine mode or equivalent terminology).
 

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Re the oil in the box ECU, that does no harm as oil,is not conductive in any way, there are thousands of MB's running around with this problem where the pilot bush has leaked.
 

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Ask the other indies. I'm sure Cole has mentioned it before on here! I do not have an answer as to why but I have seen it many times
 

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The Maf is out on its own on its own wires, all I can put it down to is when connecting jump leads, they seldom make an instant contact and sparking takes place, during the sparking components are subject to apposing voltages.

The MAF is all micro smd throughout so very tiny currents flowing, that is the only explanation that I can come up with, its plausible and many an arcing switch has blown a ECU's
 
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BachelorDays

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Re the oil in the box ECU, that does no harm as oil,is not conductive in any way, there are thousands of MB's running around with this problem where the pilot bush has leaked.

I think I'd've lost the transmission because of low oil. Once I found the flooded TCU I started to chase oil levels, etc. It needed more than a litre of oil. I had lost a 1998 E280 transmission to this problem a few years ago and after seeing the TCU this time and reading up on it, MB St Denis in Paris's long report read out to me whilst I was driving (a rented car) in Switzerland suddenly began to make sense. At the time I had listened patiently to a diagnosis suggesting oil travelling up a wiring harness etc and thought rude things about french mechanics. This time I read it all in the forums..
 
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BachelorDays

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The Maf is out on its own on its own wires, all I can put it down to is when connecting jump leads, they seldom make an instant contact and sparking takes place, during the sparking components are subject to apposing voltages.

The MAF is all micro smd throughout so very tiny currents flowing, that is the only explanation that I can come up with, its plausible and many an arcing switch has blown a ECU's

Also to be noted is the way its gone wrong. Its not the usual MAF faults.

Its died a different way so its causing a different problem?!

I just can't get over MB software killing throttle on the basis of MAF readings.
 
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