MAS Sensor?

[Flyer]

Greg, my 320's done 56k miles and is still on the original spark plugs. When it was last serviced (June), a B service, I was advised that the plugs were due around about then but I elected to leave them as I knew I could find an independent to change them cheaper.

Just checked my "Additional Work" sheet and it states:

Replace Spark Plugs

Every 18-27,000 miles / 4 years - for eng. 111.943/944/947/973/975 not model 203
Every 30-42,000 miles / 4 years - for eng. 104, 166, 111 except 111.943/944/947/951/952/955/956/957/958/973/975/981/982/983
Every 54-66,000 miles / 4 years - for eng. 111.951/952/955/956/957/958/981/982/983 and 112, 113, 119, 120, 137

Don't know which is mine, but they are definitely overdue (on age). The tech has placed a tick next to the last one.

So, yes your plugs are probably due to be changed, but sorry don't know if that would cause your problem!

Cheers
Andrew

 

[mapleleaf]

MAS update

Got my car back with new MAS sensor - and new spark plugs x 16 (which did not cure the problem but were due for changing soon anyway at 4yrs old next month.)

I'll let you know if the new MAS sensor cured the loss of power problem.

Total bill for an A service plus the above - £711 incl VAT

 

[mapleleaf]

Succes!

The car is now behaving itself like what it did when I first got it

Seamless powerer delivery and silky smooth gear changes right up to as fast as I could go before running out of road.

Costly but the MAS replacement seemed to have sorted out the problem.


:bannana:

 

[GregE240]

Thats good news Steve. Pleased to hear its okay again.

Mine is going in tomorrow for investigative work. Andy Gayle thinks it unlikely that its the MAS sensor as it only appears when the engine is cold (and damp possibly).

Plugs have been in for 45K so theres an outside chance it could be a dodgy one (or two, three etc), but Andy seems to think these plugs are good for even 50-60K (incredibly!)

Andy obviously won't know anything until the car is hooked up to the computer and the ECU checked for error codes. His initial thought was that a plug lead is on its way out - they will check all of them tomorrow for damage/shorting.

Fingers crossed! Hope its not too much of a wallet wacker (although reading about Graham and Steve's problems anything under £500 will be a small mercy)

Will let everyone know the outcome.

Cheers,

Greg

 

[Paul]

Originally posted by GregE240
The problem did NOT disappear if I turned the ignotion off and on, the other thing I found in the process is that if the car is in P, it only revs to about 4500rpm? I'm not sure if thats normal, if you're moving and you select N, you can rev it to the redline no problem.

ATB,

Greg

This maximum rev' is a safety thing I believe. My car is running perfect (he whispers ), but I have noticed in the past that in Park it will only rev' to around 4-4500rpm.

 

[Tan]

I know i have mentioned this before, but does anyone else think its a little funny that so many people have had MAS sensor problems this year??

I would be really interested to find out the cause, i rekon it may be due to the excessive heat we had this summer.

Does anyone know if they fit a different MAS sensor to cars that are destined for warmer climates??

A very confused

Tan

 

[mapleleaf]

My wifes ML lost power this morning on the motorway - wouldnt pull past 50mph with her foot flat down on the accelerator


I have a horrible feeling about this !!!

Tan maybe onto something - until recently on this forum I didnt even know what a MAS sensor was.

 

[mapleleaf]

My local dealer says that over the past 5 months they have replaced around 45 MAS sensors just on CDi engines alone !!


The ML is really bad - put a litre of oil in last night and judging by the smoke from the exhaust all the way to work (8 miles) and almost no power ... it'll need another litre.

Dealer advised I call out Mobilo and not to drive the car further.

Mobilo on their way and a hire car is to be organised.


Hopefully this could be a warranty issue

 

[GregE240]

** URGENT**

Can someone who has had a MS sensor fail either respond here or PM please ASAP please?

I could do with speaking to someone about the symptoms as Andy Gayle cannot be 100% sure and I'd rather not shell out on a new one without knowing a bit more.

If anyone can help I'll be really grateful.


Thanks,

Greg

 

[mapleleaf]

Greg

Symptoms are when you kickdown hard, the car fails to pull anything like how youd expect, in my case struggled to go past 80/90mph , then ease off the accelerator and it should carry on normally.

Why not get it into the dealership for them to check it out - you dont have to let do any actual repair work if you dont want. At least you'll know for sure what the problem is.

 

[Steve_Perry]

Greg,

What do you need to know mate? PM me if you don't want to ask in the thread and I'll see if I can answer your question.

*EDIT* some symptoms of my car when the MAS was playing up.

Lumpy idling, the engine feeling like it wasn't running on all six cylinders or all 12 sparks.

Harsh gear changes, with the car almost violently banging from 1st to 2nd and 2nd to 3rd.

Holding on to too low a gear, e.g. full throttle with Kick-down resulted in the car travelling at 75-80 mph @ 5,500 rpm and zero acceleration.

When the MAS finally failed the car was practically immobile with a top speed of 10 mph and a 0-10mph time of about 6 or 7 seconds.

P.S. I've just done 1690 miles on the Germany GTG and the pedal value sensor didn't play up once! I'll be attacking the electrical plug connector with switch clean soon, I think the sensor itself is a sealed unit. I thought of cleaning it before the GTG but would have been gutted if I had made a very intermittent problem a more regular one so left well alone.

 

[GregE240]

Well?

Thanks chaps.

Got the call this afternoon. Three letters. First one M. Second one S. Vowel in the middle A badge for us lucky MBCLUB people, maybe?

Looked at the Star printout when I got to Andy Gayle's. What an incredible piece of kit that is! Like...all the times the alarm has been activated, and by what sensor? Temp of oil and water? No problem. Stoplamp switch? It failed - once. Its alright now.

But, back to business.

Most obvious was misfiring on all cylinders as a stored error (same symptom as Steve_BCS) as well as a reduced voltage being reported by the unit itself.

Andy wasn't 100% so he phoned me to verify my symptoms before taking the car out for a road test with the Star on board. Only then did the MAS start playing up! A new MAS was put in with all "legacy" error codes cleared. One drive later......nothing reported. Sweet!

So, I'm just over £300 lighter (£201 for the part, labour, use of Star machine, new air filter) and blimey! Same as both Steves here - its like a new car. What a shame if you drive your car everyday - you just don't notice the gradual erosion of power - it was a revelation.

Thanks to all for your help and ideas.

Cheers,

Greg

 

[GregE240]

Just for the record, I got approx 98K out of my MAS sensor before it started to fail.

Seems a bit more than some of you others who've had it done? To be fair, Graham's probably failed due to the K&N issue?

Car is just amazing now - mid range torque now available in spades!

 

[mapleleaf]

On the ML Front its not the MAS sensor

Mobilo came out yesterday and it was the Turbo bearings that had failed -

We slowly drove the vehicle to the dealership where it remains till they can get the parts (on back order) but I'm driving a new E class 200 Kompressor .Classic , auto .. in Black . courtesy of Mobilo

Actually its quite a nippy motor. well, nippier than I expected it to be anyway.

 

[Dieselman]

Steve

Turbo bearings? I'd be amazed unless wifey has been in the habit of giving the car a good thrashing then turning off straight away on a really hot engine, or revving up and switching off.

My car was short of power on the RR get together so I checked a few things out.

The MAF was faulty, but not detectable in normal driving. I fitted a new MAF and the car then lost all power after about 5 mins of driving. This would reset for the next journey and then repeat.
A bit of "discussion and testing" at the dealer followed. Three visits and still not working I diagnosed the turbo wastegate was being released so losing all boost.
To be fair the dealer Tech did say new MAFs can show other problems.

The new MAF was detecting that the EGR was not operating, (I know because I blocked it), and the ECU then released the wastgate as a safety measure. My car would pull 60-70 mph depending on whether kickdown was selected or not.

I bet your ML ECU is in limp home mode having stored a fault, or the wastegate vacuum module is faulty.


I metered the MAF again today now all is working as a reference.

 

[Steve_Perry]

Originally posted by Steve_Perry
P.S. I've just done 1690 miles on the Germany GTG and the pedal value sensor didn't play up once! I'll be attacking the electrical plug connector with switch clean soon, I think the sensor itself is a sealed unit. I thought of cleaning it before the GTG but would have been gutted if I had made a very intermittent problem a more regular one so left well alone.

Well after no problems during the visit to Germany my Pedal Value Sensor has started playing up again, I drenched the sensor and plug connection in switch cleaner but that has not cured the problem. Oh well at least the problem is intermittent and the car seems okay most of the time.

S.

 

[Dieselman]

Steve

You need to get into the throttle pot. Either break the casing open and glue it back together once finished, or drill a small hole in the casing and plug it with silicone after switch cleaning it.

 

[mapleleaf]

IF it is the ECu in limp home mode then I wonder why the car is using so much oil , its churning out black smoke . Yhe Mobilo Mechanic took teh turbo unit apart to arrive at his diagnosis.

Just have to wait until the dealer gets back to me I suppose.


Would the Add on "TUNIT chipping module be the cause perhaps??

 

[Dieselman]

Possible because the extra fuelling loads the turbo more. The wastegate will still control the maximum pressure though.

You say "black smoke". Oil smoke will be blue and the engine may race away. Black smoke indicates too much fuel or too little air.

I bet you have a split air intake pipe blowing off the turbo pressure, but still shifting air through the MAF so still fuelling up, hence the black smoke. Alternatively the EGR valve is stuck open so returning too much exhaust gas.

If the turbo bearings were shot the engine will produce blue smoke especially at idle because the oil pressure is higher than the intake pressure.

Turbo bearings always have some lateral play, as they are plain bearings and the shaft floats on oil.

If the Tech ran a diagnostic my guess is that it came back "boost pressure too low", which is why he went for the bearings. It just wont happen like that.

 

[mapleleaf]

well well

just spoke to the dealer and It turns out that the catalytic convertor was blocked ! nothing to do with Turbo bearings.

New Cat fitted & I pick the car up at lunchtime.

I shake my head in dismay at the Mobilo man's diagnosis.

and diesalman - looks like you really know your stuff - thanks for the input.