Help!!!

[andystone]

Hi all, my 05 m54 2.5i is currently on a sorn and cannot be driven as cuts out upon acceleration. The car appears to go into some kind of safe mode, with the engine revs pulsating regularly until its turned off and on again. You can't drive it whilst it does this. I cannot replicate the fault whilst being stationary and revving as the car has to be moving. Inpa shows nothing in the faults, but oddly my c110 will regularly show lean codes (I'm not sure if this is related). So far in an effort to find the cause of the lean codes iv inspected the air intake pipe (was new a few years back), cleaned the maf, replaced the disa oring (vain was also previously replaced), and replaced the ccv pipes etc. Nothing is making a difference. I haven't smoked tested the system as yet. I'm pulling my hair out (if I had any)!. I did wonder if the maf is gone on, but am unsure how to test this?

Hope that makes sense and all suggestions greatly received.

 

[BumpyZ4]

Unplug the MAF and see if it runs any better.

 

[enuff_zed]

So when you accelerate it needs more fuel and sounds like it’s not getting it. Therefore runs badly and lean codes. Is the fuel pump delivering enough? Is the fuel rail pressure ok? Definitely sounds an issue with fuel delivery or the control of that.
Maf, injectors, DME, all worth looking into.

 

[HGoward]

So when you accelerate it needs more fuel and sounds like it’s not getting it. Therefore runs badly and lean codes. Is the fuel pump delivering enough? Is the fuel rail pressure ok? Definitely sounds an issue with fuel delivery or the control of that.
Maf, injectors, DME, all worth looking into.

I was about to say fuel delivery related too in regards to the low pressure fuel pump. Sounds like the G force of accelerating is causing fuel starvation.

 

[andystone]

So when you accelerate it needs more fuel and sounds like it’s not getting it. Therefore runs badly and lean codes. Is the fuel pump delivering enough? Is the fuel rail pressure ok? Definitely sounds an issue with fuel delivery or the control of that.
Maf, injectors, DME, all worth looking into.

How do I test the fuel pump etc?

 

[enuff_zed]

So when you accelerate it needs more fuel and sounds like it’s not getting it. Therefore runs badly and lean codes. Is the fuel pump delivering enough? Is the fuel rail pressure ok? Definitely sounds an issue with fuel delivery or the control of that.
Maf, injectors, DME, all worth looking into.

How do I test the fuel pump etc?

I'll be honest................. not sure. But I reckon a garage would be able to measure the pressure in the fuel rail for you.
However, for simplicity's sake I think I would be looking to at least borrow another MAF first to see if that is the issue.
As [ref]BumpyZ4[/ref] says, you could disconnect it as it will then run on a default set of values which should at least tell you if that is your fault or not.

 

[andystone]

So when you accelerate it needs more fuel and sounds like it’s not getting it. Therefore runs badly and lean codes. Is the fuel pump delivering enough? Is the fuel rail pressure ok? Definitely sounds an issue with fuel delivery or the control of that.
Maf, injectors, DME, all worth looking into.

How do I test the fuel pump etc?

I'll be honest................. not sure. But I reckon a garage would be able to measure the pressure in the fuel rail for you.
However, for simplicity's sake I think I would be looking to at least borrow another MAF first to see if that is the issue.
As [ref]BumpyZ4[/ref] says, you could disconnect it as it will then run on a default set of values which should at least tell you if that is your fault or not.

Cheers, much appreciated. I see that inpa will also test the fuel pump, there is a YouTube video I've just seen, so I'll be having a play with inpa again.

 

[Haro]

As has been said, try unplugging the maf. Failing maf can miss under load or cut out/slow. If it's under reading, you'll get a lean code.

 

[andystone]

Well, I unplugged the maf and absolutely nothing happened to the running of the engine. Is the maf dead? Also is the 'secondary air mass' the maf? Or something completely different (it doesn't move at all on the inpa).

 

[andystone]

So when you accelerate it needs more fuel and sounds like it’s not getting it. Therefore runs badly and lean codes. Is the fuel pump delivering enough? Is the fuel rail pressure ok? Definitely sounds an issue with fuel delivery or the control of that.
Maf, injectors, DME, all worth looking into.

How noisy should the fuel pump be? A gentle humming with some odd groaning when I turn it on and off using inpa.

 

[Haro]

Well, I unplugged the maf and absolutely nothing happened to the running of the engine. Is the maf dead? Also is the 'secondary air mass' the maf? Or something completely different (it doesn't move at all on the inpa).

IMG_20230209_130435.jpg

Did you take it for a drive with it unplugged? Try accelerating with it unplugged to see if it doesn't cut out/runs better. You can't diagnose it at idle, has to be under load.

 

[andystone]

Well, I unplugged the maf and absolutely nothing happened to the running of the engine. Is the maf dead? Also is the 'secondary air mass' the maf? Or something completely different (it doesn't move at all on the inpa).

IMG_20230209_130435.jpg

Did you take it for a drive with it unplugged? Try accelerating with it unplugged to see if it doesn't cut out/runs better. You can't diagnose it at idle, has to be under load.

ah OK cheers, I'll take it out

 

[andystone]

Well, disconnected the maf, took it for a spin. No lean codes and no safe mode accelerating over 3k revs (where it would normally cut out).

 

[enuff_zed]

Well, disconnected the maf, took it for a spin. No lean codes and no safe mode accelerating over 3k revs (where it would normally cut out).

New MAF needed then. Simples.

Are you anywhere near [ref]umfaan[/ref]? He may have one.

 

[andystone]

Well, disconnected the maf, took it for a spin. No lean codes and no safe mode accelerating over 3k revs (where it would normally cut out).

New MAF needed then. Simples.

Are you anywhere near [ref]umfaan[/ref]? He may have one.

I'm near Carmarthen.

 

[Umfaan]

None for a 2.5.at the moment.

 

[enuff_zed]

Stuart (bigwinn) has a 2.5 MAF if you need one.
Send him a PM?

 

[andystone]

Just a little update. I popped in a new MAF and the problem was sorted! Thanks

 

[Mike6]

Out of interest as I may have a similar problem, where did you get your maf and how much was it. I have seen them advertised from as little of 45 pounds up to several hundred pounds.

 

[andystone]

From memory it was only a cheap one (I didn’t want to spend a fortune if it didn’t fix the problem), and has been trouble free since.