N52 - Drives better without MAF but still not great

[E82_125i]

Sorry if this turns into a bit of a rant but I have yet another problem on my 125i to add the roster. Its starting to test my patience a bit as I cannot seem to get to the bottom of it and its starting to push me into wanting to sell up which I don't really want to do.

Its been ongoing I think but the throttle response has been getting really flat and it makes the car a bit tank like to drive. Its had new coils/plugs/airfilter/waterpump and thermostat in the last year or so aswell as regular oil changes and cleaning of the VANOS solenoids (they were pretty clean already) It may need new gaskets for the Eccentric Shaft Sensor and the Valvetronic Motor as they are starting to leak - Yes big eyeroll!

There's not the oomph you get with the variable valve timing like its not kicking in when the revs start to climb (used to have a Honda so think that's what's going on) And there's like a dead spot on the throttle response - like its not pulling itself along very well.

Out of curiosity I unplugged the MAF to see if it runs better and what do you know, it does! However gradually after a while it does start to feel flatter again like its adapting to something but in general better than with it plugged in and much sharper. Im wondering what the engine bypasses when its unplugged - I would say a new mass air flow sensor is the answer however im not convinced that's all that is going on.

I wouldn't say it feels slower with it plugged in but it seems to take more effort to get it to go. Ive applied MAF cleaner to sensor but it has made no difference.

Aside from MAF codes from it being unplugged, there absolutely no codes whatsoever, nothing that even looks remotely suspicious. Something I have noticed is that when you rev at idle it doesn't seem quite as keen and the cars shakes slightly when the revs drop like a very faint misfire and it can occasionally feel a bit lumpy on idle with the occasional thud once the engine gets up to temp.


I have no idea where to start and BMW Indys seem to have a horrendous waiting times at the moment - they also all seem to charge about £100 just to even diagnose it/plug it in. So I am tempted to get a copy of ISTA and buy the DCAN cable but don't want to waste efforts on it if it doesn't tell me something that I already know - are there any tests through it that might help narrow down what's going on because its driving me mad and am on the verge of swapping it for a Toyota Aygo!

Edited by E82_125i on Friday 28th July 19:51

[d_a_n1979]

Not sure if any similar to the M54 engines etc; but cam/crank and MAF sensors could go weird and cause all sorts of issues, but not throw any codes/lights!

Until you change them out (OEM BMW ONLY) you'd be chasing your tail...

I'd say if it ran better without the MAF and then it started to try and balance things out; then that's a good place to start

Unsure of who makes the OEM MAF for your N52; but stick to that make only; don't go aftermarket

[Court_S]

d_a_n1979 said:

Not sure if any similar to the M54 engines etc; but cam/crank and MAF sensors could go weird and cause all sorts of issues, but not throw any codes/lights!

Until you change them out (OEM BMW ONLY) you'd be chasing your tail...

I'd say if it ran better without the MAF and then it started to try and balance things out; then that's a good place to start

Unsure of who makes the OEM MAF for your N52; but stick to that make only; don't go aftermarket

MAF is made by Seimens VDO (or at least it was in my 130i, 125i and current 330i). Most of the sensors in the N52 are made by them.

[d_a_n1979]

Court_S said:

d_a_n1979 said:

Not sure if any similar to the M54 engines etc; but cam/crank and MAF sensors could go weird and cause all sorts of issues, but not throw any codes/lights!

Until you change them out (OEM BMW ONLY) you'd be chasing your tail...

I'd say if it ran better without the MAF and then it started to try and balance things out; then that's a good place to start

Unsure of who makes the OEM MAF for your N52; but stick to that make only; don't go aftermarket

MAF is made by Seimens VDO (or at least it was in my 130i, 125i and current 330i). Most of the sensors in the N52 are made by them.

Cheers Sam. Same as the E39 / M54s

[E82_125i]

d_a_n1979 said:

Not sure if any similar to the M54 engines etc; but cam/crank and MAF sensors could go weird and cause all sorts of issues, but not throw any codes/lights!

Until you change them out (OEM BMW ONLY) you'd be chasing your tail...

I'd say if it ran better without the MAF and then it started to try and balance things out; then that's a good place to start

Unsure of who makes the OEM MAF for your N52; but stick to that make only; don't go aftermarket

I did wonder about the cam sensors (Vanos solenoids?) Ive read up other accounts of similar behaviour to the point its made my head hurt but have narrowed it down to the following.

Throttling reset - Tried, no difference
Vanos Solenoids
Vacuum leak - Possibly but had it smoke tested a while ago with nothing to report, revs dont hunt at idle
Disa - Pulled out the largest one and no play, felt like new
Fuel pump/injectors - Quite a possible one but no way of testing from what im aware of.
The MAF itself - Ive never owned a car where this fails and it didnt appear dirty.

So it’s quite a big list of possibilities but my take away is it doesnt feel like it gets the right air fuel mixture and it has felt like this for a while. I actually had mixture control codes at the beginning of the year that went away on their own.
And unplugging the MAF just resets it back to a standard map for a while.

So is the answer to this to start firing a very expensive parts canon? All specialists I’ve encountered advise agsinst this and say wait for more engine codes but nothing ever comes.

Is there anyway to try and narrow this down with specialist software that i could potentially use?
I think if not id rather just buy an old shed and run it into the ground rather than plough money into a problem that i could be chasing constantly.

[d_a_n1979]

E82_125i said:

d_a_n1979 said:

Not sure if any similar to the M54 engines etc; but cam/crank and MAF sensors could go weird and cause all sorts of issues, but not throw any codes/lights!

Until you change them out (OEM BMW ONLY) you'd be chasing your tail...

I'd say if it ran better without the MAF and then it started to try and balance things out; then that's a good place to start

Unsure of who makes the OEM MAF for your N52; but stick to that make only; don't go aftermarket

I did wonder about the cam sensors (Vanos solenoids?) Ive read up other accounts of similar behaviour to the point its made my head hurt but have narrowed it down to the following.

Throttling reset - Tried, no difference
Vanos Solenoids
Vacuum leak - Possibly but had it smoke tested a while ago with nothing to report, revs dont hunt at idle
Disa - Pulled out the largest one and no play, felt like new
Fuel pump/injectors - Quite a possible one but no way of testing from what im aware of.
The MAF itself - Ive never owned a car where this fails and it didnt appear dirty.

So it’s quite a big list of possibilities but my take away is it doesnt feel like it gets the right air fuel mixture and it has felt like this for a while. I actually had mixture control codes at the beginning of the year that went away on their own.
And unplugging the MAF just resets it back to a standard map for a while.

So is the answer to this to start firing a very expensive parts canon? All specialists I’ve encountered advise agsinst this and say wait for more engine codes but nothing ever comes.

Is there anyway to try and narrow this down with specialist software that i could potentially use?
I think if not id rather just buy an old shed and run it into the ground rather than plough money into a problem that i could be chasing constantly.

TBH I'd replace the MAF first; my hunch is that'll sort it.. If not then cam/crank sensors

MAF cleaners don't work IMO; once they start to fail, there's no fixing...

[bmwmike]

Needs a look at live data via INPA to see fuel trims, O2, etc and not just throwing parts at it. Just my 2c.

Checked to see if the brakes are binding? Sounds daft but honestly I'd rule everything out first before plumping out on hunches.

[bigdom]

Agree on the MAF, once they play up, just replace, I had similar issue on an Audi before.

Whilst there is a wait for most indy's, those weeks do pass quite quickly. It appears you've been chasing something for quite a while, and may have already changed parts that didn't need doing. I see you're in Surrey, but it's a big place. My local specialist TWG in Camberley normally has minimum of 4 week wait. Will and the team are very good and don't change parts or 'find' work.

[Mr Tidy]

Will at TWG definitely knows his BMWs. I've taken mine there several times.

Alternatively you might get an earlier booking just further along the A30 at RBM Hampshire in Hook, Hants. Like Will Ross is also ex-Sytner so I've visited there several times too!

[E82_125i]

bmwmike said:

Needs a look at live data via INPA to see fuel trims, O2, etc and not just throwing parts at it. Just my 2c.

Checked to see if the brakes are binding? Sounds daft but honestly I'd rule everything out first before plumping out on hunches.

No brakes binding but funnily enough i noticed an odd observation yesterday, that with the maf plugged in the brakes feel slightly spongier! Not sure of its even possible for the two to be linked but i swear they lose some bite.

As per fuel trims, with my current diagnostics app i can monitor them. Just pootling around the long term fuel trims sit at around -7% or so and if im right the short term ones need to sit around 0% ? Im not sure how to interpret them unfortunately.

One thing i will say with the MAF as it currently is the throttle does feel smoother and the economy is better but theres still that annoying dead spot when only pressing the throttle lightly - does the mass airflow sensor have any link to the disa valves by any chance?.

Edited by E82_125i on Sunday 30th July 08:56

[E82_125i]

Ive got in touch with TWG and am just waiting to hear back. Hopefully they have courtesy cars!

Well after a longer drive at the weekend and some 99 ron in the tank its started to drive a bit better and the idle feels less lumpy after cleaning the MAF and the ESS. Which unfortunately has a small amount of oil in but not terrible.

However something that is a cause of a concern is my oil consumption…I topped up a quart last month and im already down halfway after driving it this weekend. Of course i do have the valvetronic gasket leak but this seems excessive. Im wondering if my CCV is on its way out or something worse like piston rings etc which if it is i think its game over for me…

[E82_125i]

Sorry to revive this. Think i might be on to something with the MAF as ive run it for a while without and there’s a noticeable improvement- but want to see how i go about ruling other things out first.
As fuel trims show it’s running slightly rich my guess is that i can rule out an air leak?
So im presuming i need to rule out 02 sensors and injectors ideally first before i go buying a new maf.

Im trying to get down to TWG but its a long wait so im doing some ruling out beforehand, as the MAF alone is quite expensive.

[Funk]

It's worth checking you don't have a hole in the intake boot after the MAF sensor first. If not and it runs better without the MAF then it's likely duff, get it replaced. I made the mistake of buying aftermarket when I replaced mine in my E36 and they don't last, as others have said, buy genuine BMW parts for things like MAF and other sensors or you'll be forever chasing issues.

Edited by Funk on Friday 6th October 11:33

[d_a_n1979]

As I've said and others; replace the MAF - OEM ONLY, not aftermarket versions

[Big_Dog]

I have a 330ci that ran rich with a big hole in the intake boot. Might be worth a go with a can of brake cleaner.

[Ed.Neumann]

As said above, if you have unplugged the MAF and it runs even slightly better, replace it with a new genuine one.

I would also reset all adaptations too on the DME, you could try this before a new maf if you have something to reset them with.
Should be done when changing MAFs, solenoids, sensors etc. if the car has been running for a while out of sync trying to adapt to it being out of sync.

[naturalaspiration]

If you have no error codes your VANOS solenoids should be working ok. I have seen a case where someone has mixed up the wires of the big and small DISA units...the engine was gutless, and no error codes were present.

Troubleshooting is a game of elimination. If you clear the adaptations , plug back the MAF, what sort of fuel trim readings do you get? And do the precat sensors toggle between rich and lean readings (both banks)?

Edited by naturalaspiration on Monday 9th October 20:19

[E82_125i]

naturalaspiration said:

If you have no error codes your VANOS solenoids should be working ok. I have seen a case where someone has mixed up the wires of the big and small DISA units...the engine was gutless, and no error codes were present.

Troubleshooting is a game of elimination. If you clear the adaptations , plug back the MAF, what sort of fuel trim readings do you get? And do the precat sensors toggle between rich and lean readings (both banks)?

Edited by naturalaspiration on Monday 9th October 20:19

It looks like the plugs are correct on DISA. My guess is they've never been touched. Ive ordered a used MAF for my exact model off eBay that was cheap as im not one hundred percent convinced it is the MAF. Regardless of it plugged in or not, the fuel trims seem to spend the majority of the time in negative on both banks.

In terms of clearing adaptations how does one go about this. I have INPA on an old laptop but will be honest, I only do diagnostics through it as I heard that you can cause damage to the car if you're not careful!

[R129 300SL]

Unplugging the MAF usually puts car into a failsafe running mode using preset data points instead of the variable readings from a functioning MAF.

If it runs better without it plugged in chances are that's the fault.

It won't run perfectly unplugged because it runs a preset fixed program. Almost like a failsafe to allow one to get home.

[d_a_n1979]

R129 300SL said:

Unplugging the MAF usually puts car into a failsafe running mode using preset data points instead of the variable readings from a functioning MAF.

If it runs better without it plugged in chances are that's the fault.

It won't run perfectly unplugged because it runs a preset fixed program. Almost like a failsafe to allow one to get home.

The OP seems to be persistent in the sense that they're not going to buy a new MAF until they've failed with everything else...

More or less everyone has said replace the MAF; but it's still not been done yet...