Likely MAS/ECU issue?

[Shude]

On Friday I was driving to work and on the way up a hill the car seemed to lose a bit of power and the gearbox shifted a little strangely. I came to a stop at the top of the hill in a queue for the motorway sliproad and as the revs dropped the engine sounded seriously rough, the whole car shook a little as the poor thing ticked over on what felt like 3 cylinders out of 4, so uneven it felt like it was about to stall! The traffic lights went to green and I had no choice but to continue onto the motorway and as the speed reluctantly increased it sounded a little smoother so I drove at about 60mph-ish about 5-10 miles to huddersfield where I turned off, parked up and killed the engine. Put the key back in, turned it and it was fine, sounded great. It did it again on Sunday, twice, both times fixed by simply starting the engine again.

It did it again today and I noticed that the gearbox doesn't seem to like the erratic change in performance as it struggled to work out what I was trying to do, pedal was about 2/3 down but performance was low so it shifted kinda strangely!

I know this has happened to other people, I searched for an answer but MAS/MAF and ECU are TLAs and therefore have too few letters to search with!

GrahamC230k / Steve Perry - I know you guys have had ECU or MAS/MAF issues before, do either of these sound the likely cause?

The car is due for the biggest service in history in a month so I can get it sorted out then hopefully...

P.S. the sound of the poor engine running on only 3 cylinders with the supercharger blasting air through them is hilarious, sounds like a podracer or something!

 

[R2D2]

I accept it is more likely to be ECU/MAF but have you checked that your gearbox plug isnt leaking oil. It could be that the gearbox is confusing the engine! Either way sorry to hear of your woes

 

[C240Sport97]

This is exactly what happened to my car when the MAS thing went South. It first started with the bad gearchanges, then hesitant pulling, then downright no power. Over a period of about 3 months. It died slowly. And it cost £418 at a stealer 'all in'. Ouch!

 

[Shude]

So we're pretty certain it's the MAS/MAF then? Car is just over 6 years old and has done 112000 miles so I suppose it's not too unlikely for it to start giving up. From what I read it's practically a consumable and it's probably lucky that it's lasted this long! *sigh*

 

[C240Sport97]

well, mine lasted 6 years and 50k miles

 

[nickmann]

This is exactly what happened to my car when the MAS thing went South. It first started with the bad gearchanges, then hesitant pulling, then downright no power. Over a period of about 3 months. It died slowly. And it cost £418 at a stealer 'all in'. Ouch!

What sort of "bad gearchange"? I've got an issue at the moment with the change from 3rd to 4th. If the temp guage is between 1/4 and normal, and the change occurs between 2000 and 3500rpm then the change is flawed. It goes from 3rd to 4th, then back, then to 4th again. Almost imperceptible, but noticeable if you are looking at the revcounter, or driving with the radio off.

It's been to the dealer for computer and mechanical check - no boxfaults found, one dicky reading from one of the lambda sensors. Fluid change was about 2000 miles ago.

I am hoping it is the MAS because that is easily diagnosed, after its completely failed anyway, and should be simple to fix. I'm hoping its nothing to do with the box as that is going to be more complicated.

 

[DITTRICH]

well, mine lasted 6 years and 50k miles

5 years 70k miles
Les

 

[C240Sport97]

The change was very jerky ...

And it was not temperature related.

But it did hunt a few times between gears.

if it is the MAS, you will eventually suffer serious power loss.

What sort of "bad gearchange"? I've got an issue at the moment with the change from 3rd to 4th. If the temp guage is between 1/4 and normal, and the change occurs between 2000 and 3500rpm then the change is flawed. It goes from 3rd to 4th, then back, then to 4th again. Almost imperceptible, but noticeable if you are looking at the revcounter, or driving with the radio off.

It's been to the dealer for computer and mechanical check - no boxfaults found, one dicky reading from one of the lambda sensors. Fluid change was about 2000 miles ago.

I am hoping it is the MAS because that is easily diagnosed, after its completely failed anyway, and should be simple to fix. I'm hoping its nothing to do with the box as that is going to be more complicated.

 

[Steve_Perry]

Hi Nick,

Your symptoms sound identical to mine and what I would term as classic MAS failure indicators... Lumpy idle, lack of power, weird gear changes banging or even sticking in gear and not changing up. As always, a Star Diagnose will confirm the issue.

My thread when mine bit the dust is here...

http://mbclub.co.uk/forums/showthread.php?t=2507&highlight=glitched

S.

*EDIT* P.S. If it's any consolation your car will feel like it has been chipped and given another 20BHP after you've had a new MAS fitted.

 

[nickmann]

Hi Nick,

Your symptoms sound identical to mine and what I would term as classic MAS failure indicators... Lumpy idle, lack of power, weird gear changes banging or even sticking in gear and not changing up. As always, a Star Diagnose will confirm the issue.

My thread when mine bit the dust is here...

http://mbclub.co.uk/forums/showthread.php?t=2507&highlight=glitched

S.

*EDIT* P.S. If it's any consolation your car will feel like it has been chipped and given another 20BHP after you've had a new MAS fitted.

Yes I had the car put on the diagnostic - but no fault. well, only one of the lambda sensors was showing a ?. Not a fault, but a query.

 

[Steve_Perry]

Yes I had the car put on the diagnostic - but no fault. well, only one of the lambda sensors was showing a ?. Not a fault, but a query.

Heh, sorry my post above was directed towards Shude (aka Nick) I should have used his screen handle.

S.

 

[Shude]

I will see if Whitefield can slip it in for a 5 minute diagnostic on Saturday morning!

 

[Steve_Perry]

I will see if Whitefield can slip it in for a 5 minute diagnostic on Saturday morning!

I'd bet my dinner tonight it's the MAS on its way out

S.

P.S. You'll have to try and induce symptoms I think, I can't remember whether MAS faults are stored in the log or not. I know for a fact that pedal value sensor faults aren't so whenever I took the car along they never found a problem until I took the car to them with the fault active. Sheesh I still haven't had that one resolved

 

[silverarrow]

remember to buy your maf mas from bosch agent (andrew page in bury )only £100 all in and 10 mins to fit mine did 80 k and 4 yrs.
did you know mafs can be a recon part for only a few quid www.bba-reman.com not used them myself

 

[Mambo]

Sounds like MAS to me, mine only lasted 4 years/36,000 miles

 

[Shude]

You'll have to try and induce symptoms I think, I can't remember whether MAS faults are stored in the log or not.

Pulling onto the motorway has done it every time! There is motorway between me and the stealership so I can have it popping and juddering away in time for someone remotely technical to see it happening.

This is the part that Graham bought:

A0000940948 : AIR MASS SENSOR : EUR 321.83

Diagram:

 

[big x]

Prince of darkness

Lucus used to be called this but since 1998 or so Bosch deserve the title due to failing electronics they supply to Merc,BMW, Audi, peugeot etc.
I was looking at a motoring mag from 1999 the other day and a German engineer from one of the car makers was complaining that the Bosch air flow meters using hot wire technology where far short of Hitatchi's design in reliability.Audi where pissed off that a large batch of bosch ignition coils had a 100% failure rate which cost them a fortune in call out breakdown repairs.
A funny lot the Germans,for political reasons they would rather sit broken down at the side of the road than buy in Japanese made parts.

adam

 

[C240Sport97]

bloody good deal .. 25% of what I paid!!!!!!

remember to buy your maf mas from bosch agent (andrew page in bury )only £100 all in and 10 mins to fit mine did 80 k and 4 yrs.
did you know mafs can be a recon part for only a few quid www.bba-reman.com not used them myself

 

[Shude]

remember to buy your maf mas from bosch agent (andrew page in bury )only £100 all in and 10 mins to fit mine did 80 k and 4 yrs.

Ahh, those guys are about 5 miles from me! I need to call them!

 

[big x]

£400 !

One of the reasons Bosch introduced the hot wire meter was to reduce costs over the old airflow meters which used flaps on spindles which where expensive to machine and also needed periodic cleaning to work properly.
The hot wire system is supposed to burn off deposits.Fine in theory but in practice they can be short lived.Not really a problem as these new meters are simple and getting cheaper as they are made in the millions and are all very similar model to model.I would imagine the wholesale price would be circa £30 or so from one of Bosch's eastern european factories.I don't know how the smarmy suits at mercedes sleep at night looking at their mark ups.

adam