New MAF - new lease of life
Discussion
My cars been underperforming for the last month now and I knew something was wrong but it was quite driveable around town and I needed it. Under 4k revs it was fine but above that it felt like some kind of fuelling problem. As I say though, I'd kind of got used to it and knew it would be sorted soon enough.
So I've been putting up with it for a while untill today when it was fixed at an OPC under warranty - MAF failure.
I'd forgotten quite how good the 996 really was
- took it up the A3 and really opened it up and I jsut grinned my head off - fantastic feeling 
I'd also forgotten how addictive the engine at high revs is.
So anyway, I'm happy again.
So I've been putting up with it for a while untill today when it was fixed at an OPC under warranty - MAF failure.
I'd forgotten quite how good the 996 really was
- took it up the A3 and really opened it up and I jsut grinned my head off - fantastic feeling I'd also forgotten how addictive the engine at high revs is. So anyway, I'm happy again.
MAF = service item. Bit like pads & disks. Mine went at 40k and when changed transformed the performance.
When I did mine was told on here that the Porsche unit at £250 is the same as the Bosch unit at £120. I'd already bought a Porsche one but next time I have problems I'll be using the Bosch item.
When I did mine was told on here that the Porsche unit at £250 is the same as the Bosch unit at £120. I'd already bought a Porsche one but next time I have problems I'll be using the Bosch item.
I changed mine when I first bought the turbo because I'm sick of fannying about with the things -- M5 had two gone, M3 before that needed one. They're a nightmare, just decided to change it in case it was knackered.
However, mine didn't make a jot of difference so I have a confirmed good second hand one if anyone wants to buy it.
SM
However, mine didn't make a jot of difference so I have a confirmed good second hand one if anyone wants to buy it.
SM
rumplestiltskin said:
G;ad its sorted.
Could you describe the symptoms you experienced ?
R.
009 was pretty accurate in his description - I found that the flatspot could be eliminated by coming off the throttle a bit though. It also seemed that the revs were limited to about 6-6.5k.
If in doubt get it checked though
I had a spasmodic misfire on the tt that felt like it was dropping on to 3 cylinders,most experts thought it was knackered plugs however before i took half of the car to pieces and changed the plugs i decided to clean the maf.It improved but not totally..bought a new maf which took 2 mins to fit and now is perfect...( my local Opc actually lent me a maf to try first to avoid wasting money if it didnt cure the problem which i thought was a good gesture by them.)
Changed mine myself last year, about 45k miles, as mentioned above, should be treated as a serviceable item, they certainly are in Subaru-land.
Prob on my car was mis-diagnosed by a reputed indy porsche specialist as being the two Lamda sensors on the headers...£450 later and 50 miles down the road (ie after the ECU has reached the limits of its offset) the same old prob came back again.
Not chuffed, and having replaced both Lamda and MAF on the Sub Type-R, decided to get a MAF thro a mate who works for Bosch....£90 to me...goes someway to offsetting the mis-spent £450 I guess 
Prob on my car was mis-diagnosed by a reputed indy porsche specialist as being the two Lamda sensors on the headers...£450 later and 50 miles down the road (ie after the ECU has reached the limits of its offset) the same old prob came back again.
Not chuffed, and having replaced both Lamda and MAF on the Sub Type-R, decided to get a MAF thro a mate who works for Bosch....£90 to me...goes someway to offsetting the mis-spent £450 I guess Couple of points. The limp home mode is severe and caused when something is seriously wrong. A MAF that's going out will last *forever* without logging a fault. You'll not get to 6krpm in limp home mode.
The reason for poor high rpm performance is that more air is coming in than the engine realises and it becomes progressively more lean as the MAF signal deterioates. Both my M3 and M5 had aborted dyno runs on dodgy MAFs owing to "dangerously lean" mixture. I think the lambda sensors will not allow the mixture to get that dangerously lean though and allow the ECU to bring in a little extra fuel.
There is no wire. These are state of the art thin film jobbies. You can clean them as described but the improvement will be short lived and (I'm told) the MAF may deteriorate more than when you cleaned it last time. I reckon there's some sort of protective layer on there which is scrubbed off when you clean it.
I'm also told that if you suspect a MAF failure, disconnect it and run the car to see if it's better or worse or the same. The BMW tech did this with my M5 and it was the same indicating that the ECU was ignoring its input and using some default from the throttle pos/intake temperature/etc readings.
They can be tested by a technician with a high speed oscilloscope -- Clive Atthowe in Norwich did the ones on my M5. With the engine running he did a snap throttle open thing and looked at the traces. I don't really know what he saw but he said they were a)different and b)wrong. Never had him test the new ones for comparison.
SM
The reason for poor high rpm performance is that more air is coming in than the engine realises and it becomes progressively more lean as the MAF signal deterioates. Both my M3 and M5 had aborted dyno runs on dodgy MAFs owing to "dangerously lean" mixture. I think the lambda sensors will not allow the mixture to get that dangerously lean though and allow the ECU to bring in a little extra fuel.
There is no wire. These are state of the art thin film jobbies. You can clean them as described but the improvement will be short lived and (I'm told) the MAF may deteriorate more than when you cleaned it last time. I reckon there's some sort of protective layer on there which is scrubbed off when you clean it.
I'm also told that if you suspect a MAF failure, disconnect it and run the car to see if it's better or worse or the same. The BMW tech did this with my M5 and it was the same indicating that the ECU was ignoring its input and using some default from the throttle pos/intake temperature/etc readings.
They can be tested by a technician with a high speed oscilloscope -- Clive Atthowe in Norwich did the ones on my M5. With the engine running he did a snap throttle open thing and looked at the traces. I don't really know what he saw but he said they were a)different and b)wrong. Never had him test the new ones for comparison.
SM
johnfm said:
£342.33 + VAT for the GT3 MAF sensor!!!! I think I'll get it put on a scope first at that price!
John, have a look on the sensor and see if there's a Bosch part number (ie a number that isn't the usual Porsche 996 xxx xxx format, is prob the one you're after) then see if any decent motorfactors can get you one (or try here www.eurocarparts.com/ ) Not sure if the GT3 item is same as the C2, but if so, then it's a 5min job with a torx screwdriver/socket-bit.
Have a read over on the BMW forum and m5board.com, you'll find someone there got the "same" part from Bosch and it didn't work properly.
The M5 has a dashboard test mode that allows you to sort of test the MAFs sadly it seems the 996 doesn't.
I don't think I'd buy a non-porsche part as important as the MAF just to save a few quid because I'd never be certain it was right. You really don't want a lean mixture at 8000rpm.
These cars aren't Toyota Corollas you know
SM
The M5 has a dashboard test mode that allows you to sort of test the MAFs sadly it seems the 996 doesn't.
I don't think I'd buy a non-porsche part as important as the MAF just to save a few quid because I'd never be certain it was right. You really don't want a lean mixture at 8000rpm.
These cars aren't Toyota Corollas you know
SM
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