craigdiver
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| posted on 13/7/18 at 04:46 PM |
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MAF knackered
Hi all, after spending ages diagnosing idling issues on my BMW powered haynes roadster it turns out that I think the MAF is knackered. Plugged in it
idles really rough and stalls if you try to rev it. unplugged the engine runs ok and revs (but quite rich).
Does this point to a faulty MAF and do I replace it with a £22 ebay special, the £160 siemens oem one or some other reputable manufacturer of MAFS
(Its a Siemens 5WK9605, BMW part no 1432356).
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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craigdiver
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| posted on 13/7/18 at 04:48 PM |
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I have tried carefully cleaning it with MAF cleaner but no change
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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mcramsay
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| posted on 13/7/18 at 06:32 PM |
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Got exactly the same issue on my m3 marlin, suspected the MAF was bad and bought the 40 quid eBay special from Latvia... absolute rubbish, just made
the car run extremely rich.
Waiting for payday to buy the 160 quid Bosch one
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craigdiver
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| posted on 13/7/18 at 06:42 PM |
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quote:
Originally posted by mcramsay
Got exactly the same issue on my m3 marlin, suspected the MAF was bad and bought the 40 quid eBay special from Latvia... absolute rubbish, just made
the car run extremely rich.
Waiting for payday to buy the 160 quid Bosch one
I’m far from a car mechanic and have limited experience with engines. I’m concerned that unplugging the MAF which seems to make it run rich. Could
this be masking a different issue and not actually the MAF thats faulty? Any mechanics out there that would confirm that they would swsp out the MAF
with these symptoms?
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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steve m
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| posted on 13/7/18 at 07:05 PM |
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I bought a cheap Maf sensor for my Mondeo tdci, and wish I had bought a genuine one, as ive had no end of problems, with engine lights and limp modes,
all going back to the maf obd codes,
I will be buing a genuine Ford item soon
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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mcramsay
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| posted on 13/7/18 at 07:11 PM |
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Unplugging the MAF will make the car run rich as the ecu will default to a base Alpha-n map which ignores the input from the MAF. Instead of
determining the best fueling mix for the amount of air going in. So running rich with it unplugged is normal. But if you had an air leak on the intake
this rich condition may mask it
I would check for intake leaks and make sure the IACV is clean and working and that the throttle position sensor is working correctly. A simple
resistance check of the TPS will tell you this. The values will be on the net somewhere
If that fails swap the MAF
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craigdiver
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| posted on 13/7/18 at 07:58 PM |
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quote:
Originally posted by mcramsay
Unplugging the MAF will make the car run rich as the ecu will default to a base Alpha-n map which ignores the input from the MAF. Instead of
determining the best fueling mix for the amount of air going in. So running rich with it unplugged is normal. But if you had an air leak on the intake
this rich condition may mask it
I would check for intake leaks and make sure the IACV is clean and working and that the throttle position sensor is working correctly. A simple
resistance check of the TPS will tell you this. The values will be on the net somewhere
If that fails swap the MAF
That was my concern that unplugging the MAF would also mask any air leaks. I’ve had the ICV off this evening and gave it a good clean with carburettor
cleaner - need to see if I can cycle the valve with the BMW diagnostic software INPA. The TPS is on the throttle body and I should be able to read the
analog value with INPA.
I’ve already replaced one split vacuum tube and done a smoke test but still can’t help thinking there is something else causing the rough running. Ill
check to see what I can read off the MAF on the diagnostic software.
Thanks for your help, going to hold off buying a new MAF until I can do some more checks.
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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tims31
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| posted on 13/7/18 at 07:59 PM |
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Could you not get one from a scrappy as that would be cheaper?
Also, have you tried seeing if there are any fault codes using a OBDII reader and the Torque app? Also with Torque you can see what airflow the MAF
meter is reading.
Build: http://www.martinsfurybuild.co.uk/
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craigdiver
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| posted on 13/7/18 at 08:10 PM |
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quote:
Originally posted by tims31
Could you not get one from a scrappy as that would be cheaper?
Also, have you tried seeing if there are any fault codes using a OBDII reader and the Torque app? Also with Torque you can see what airflow the MAF
meter is reading.
I’ve got INPA BMW diagnostics on my laptop - tells you everything and lets you manually operate valves, actuators, electronic thermostst etc., ill
take a look tomorrow.
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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mcramsay
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| posted on 13/7/18 at 08:13 PM |
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You can see TPS and MAF values on INPA. I would have a look at what the short and long term fuel trims are doing on INPA aswell that will give you an
idea of how far out your fueling is. Normally if you have an air leak you will see a high +number as the ecu tries to compensate for the unmetered
air. It should drop back to normal values when you apply throttle as the the leak will be masked, unless it’s a big leak.
Been messing around with the exact same things on my car this week with INPA and DIS GT1. These are used by bmw dealers and can read many more codes
and values than the generic Obd readers/torque app I’ve got quite good with them both so if you need a hand let me know. I was reading up on this last
night and may be some help
http://wiki.bavariantechnic.com/index.php?title=Engine_Mixture_Adaptations
MAFs seem to be almost a service item on BMW’s so I wouldn’t be surprised if it needed done
[Edited on 13/7/18 by mcramsay]
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craigdiver
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| posted on 13/7/18 at 09:09 PM |
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quote:
Originally posted by mcramsay
You can see TPS and MAF values on INPA. I would have a look at what the short and long term fuel trims are doing on INPA aswell that will give you an
idea of how far out your fueling is. Normally if you have an air leak you will see a high +number as the ecu tries to compensate for the unmetered
air. It should drop back to normal values when you apply throttle as the the leak will be masked, unless it’s a big leak.
Been messing around with the exact same things on my car this week with INPA and DIS GT1. These are used by bmw dealers and can read many more codes
and values than the generic Obd readers/torque app I’ve got quite good with them both so if you need a hand let me know. I was reading up on this last
night and may be some help
http://wiki.bavariantechnic.com/index.php?title=Engine_Mixture_Adaptations
MAFs seem to be almost a service item on BMW’s so I wouldn’t be surprised if it needed done
[Edited on 13/7/18 by mcramsay]
What is DIS GT1 used for?
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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mcramsay
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| posted on 13/7/18 at 09:24 PM |
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It’s the dealer software. It allows tests to be performed on different things on the car, and can run test procedures based on fault codes. Ie you can
test the MAF by performing the MAF sensor check and it will give live voltage readings of the MAF at different rpms and tell you if it’s within
spec
The level of testing depends on the age of your car. On my m3 I can perform a vanos test procedure where it leak checks the vanos and checks the
required angles are achieved in the correct time. It also links with the bmw TIS (technical documents) so you can read up on fault codes and how
things are supposed to work.
Great tool, I bought my version from B cables on eBay which with INPA, GT1 and the workshop manuals / TIS documents. Must have if you own a bmw!
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craigdiver
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| posted on 13/7/18 at 09:26 PM |
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quote:
Originally posted by mcramsay
It’s the dealer software. It allows tests to be performed on different things on the car, and can run test procedures based on fault codes. Ie you can
test the MAF by performing the MAF sensor check and it will give live voltage readings of the MAF at different rpms and tell you if it’s within
spec
The level of testing depends on the age of your car. On my m3 I can perform a vanos test procedure where it leak checks the vanos and checks the
required angles are achieved in the correct time. It also links with the bmw TIS (technical documents) so you can read up on fault codes and how
things are supposed to work.
Great tool, I bought my version from B cables on eBay which with INPA, GT1 and the workshop manuals / TIS documents. Must have if you own a bmw!
I have the b cables software but only installed INPA, will give it a go tomorrow
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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mcramsay
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| posted on 13/7/18 at 09:41 PM |
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It’s not very user friendly! Pm me if you need some help
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craigdiver
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| posted on 13/7/18 at 10:04 PM |
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quote:
Originally posted by mcramsay
It’s not very user friendly! Pm me if you need some help
Tried running it, opened ok in a virtual window. Will hook it up to my car tomorrow and see what happens!
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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Irony
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| posted on 16/7/18 at 07:43 AM |
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My Ford C-Max for some unknown reason used to chomp through MAF sensors. It had a new one every six months. I bought new at well over £100 and then
got fed up and bought used but genuine of eBay from a breaker (£25). Always performed reasonably well.
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craigdiver
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| posted on 16/7/18 at 08:33 AM |
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quote:
Originally posted by Irony
My Ford C-Max for some unknown reason used to chomp through MAF sensors. It had a new one every six months. I bought new at well over £100 and then
got fed up and bought used but genuine of eBay from a breaker (£25). Always performed reasonably well.
Good advice, took your advice and just bought a used genuine siemens OEM one off of ebay. I also have a new crankcase breather valve on order to rule
that out too as a common failure item along with its associated vacuum pipework.
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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