P38 DSE Airmass/MAF craziness.....

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S

Spooner

New Member
Posts
62
Location
West Midlands,UK
Hey Guys

I have a 1998/99 P38 2.5 DSE.

My MPG hasn't been great, and power a little flat, so I went outside and unplugged the MAF sensor.

On a test drive its made no difference, in fact it picks up slightly better...

The other problem I have (don't know if its related) is that the engine never revs past 3200rpm...is this normal on a auto 2.5DSE?

Is the MAF common issue on this engine?

Thanks!
 
MAF's can fail on all engines, the same units are used on many different marques. Can't say I've seen any reports of MAF failure on the BMW lump tho.
Mine revs to the red line if I floor the throttle, I would gues that the engine ECU is limiting power for safety as something is wrong. You need to get plugged in and have the faults read.
Just a thought, check your in tank pump is working properly, do a current draw check.
 
Spooner said:
Hey Guys

I have a 1998/99 P38 2.5 DSE.

My MPG hasn't been great, and power a little flat, so I went outside and unplugged the MAF sensor.

On a test drive its made no difference, in fact it picks up slightly better...

The other problem I have (don't know if its related) is that the engine never revs past 3200rpm...is this normal on a auto 2.5DSE?

Is the MAF common issue on this engine?

Thanks!
Click to expand...
Sounds like the number four injector either has a bad electrical connection or has failed putting engine into safe mode. Also check eletrical connection and pressure pipe connection to MAP sensor on bracket next to fuel filter.
 
Spooner said:
Cheers Guys.

Its just had a brand new no4 injector fitted.

Is it not strange that performance stays the same with the MAF unplugged?
Click to expand...

There is a MAF on the EGR equipped engines but not on the none EGR. Depends on the year of your motor. Yours will have a MAF. The MAF only controls the EGR operation. Nothing to do with fueling as such. Look at your new # four injector engine sounds to be in safe mode. Check MAP sensor.Check for delaminations in turbo pipes. Get fault codes read as Data says. But there are lots of things you can try before spending money on a diagnostic.
 
Last edited:
wammers said:
The thing you call the MAF is not a mass airflow sensor. It houses the inlet air temperature sensor only. Being a turbo engine it does not have a MAF this function is controlled by the MAP (manifold absolute pressure) sensor. As with any other modern diesel engine throttling is controlled by fuel supply not by air supply. There is no throttle body. If it is not reving past 3200 rpm i would have a look at your new number four injeactor. The engine appears to be in safe mode. But you could check the turbo pipes internally to make sure there is no delamination causing air starvation. That would normally cause the pipe to the manifold to collapse. As Data says getting the faults read is a good idea if you can't find anything obvious from the foregoing.

Just to clarify there is a MAF on the EGR equipped engines but not on the none EGR. How did i forget to mention that, depends on the year of your motor. Sorry. Yours will have a MAF.
Click to expand...

You had me worried there Wammers cos mine has definately got what looks like a MAF, never quite understood why because as you say there is no throttle function on a diesel but of course the air flow will vary with revs. Must look at my 96 spares dog that hasn't got the EGR to see if that has a MAF
 
Hi Guys

Mine has an EGR and MAF.

A Land Rover technician told me the MAF does effect fuelling according the air temp detected by the MAF so it can cause issues if knackered.

I have run a fault check and nothing comes up, so I would be surprised if its in safe/limp mode.

It feels reasonably nippy on kick down, but doesn't do much without alot of throttle pedal input...is this the norm on the DSE auto models?
 
Datatek said:
You had me worried there Wammers cos mine has definately got what looks like a MAF, never quite understood why because as you say there is no throttle function on a diesel but of course the air flow will vary with revs. Must look at my 96 spares dog that hasn't got the EGR to see if that has a MAF
Click to expand...

Yeah i know went off on a tangent. MAF on the turbo diesel is not used in the same way as MAF on the petrol version. The air does vary with revs but that part of fuelling is controlled by MAP sensor. It's difficult to explain and i got tied up so deleted it.:D:D:D
 
Spooner said:
Hi Guys

Mine has an EGR and MAF.

It feels reasonably nippy on kick down, but doesn't do much without alot of throttle pedal input...is this the norm on the DSE auto models?
Click to expand...


Yeah, thats why people think it's slugish, it needs a lot of throttle movement to get results, but then it goes if it's chipped:D
 
Spooner said:
Hi Guys

Mine has an EGR and MAF.

A Land Rover technician told me the MAF does effect fuelling according the air temp detected by the MAF so it can cause issues if knackered.

I have run a fault check and nothing comes up, so I would be surprised if its in safe/limp mode.

It feels reasonably nippy on kick down, but doesn't do much without alot of throttle pedal input...is this the norm on the DSE auto models?
Click to expand...

Yes because it controls the EGR, but it will not or should not restrict the engine to 3200 rpm only thing i know of that does that is the # four injector going down, some sort of air starvation or the MAP not working.
 
Datatek said:
You had me worried there Wammers cos mine has definately got what looks like a MAF, never quite understood why because as you say there is no throttle function on a diesel but of course the air flow will vary with revs. Must look at my 96 spares dog that hasn't got the EGR to see if that has a MAF
Click to expand...

It should just have an inlet air temp sensor under the front left side of the manifold where turbo pipe connects. Basically where the EGR valve is on your newer one.
 
Spooner said:
Thanks guys, I will look further into this....

I have a brand new in tank fuel pump ready to fit here....does anyone know how this is done??
Click to expand...

You can take the tank out or cut an hole in the floor. Personally would remove the tank. Search the site there is a description on cutting floor with measurements somewhere.
 
I ended up cutting the floor to get to the fuel pump. Worked perfect and tidy! It feels slightly better on intial pick/ and 1/4 throttle.

After changing the pump my fuel gauge was showing 1/2 full, where as it was just under 1/4 tank with the old pump???
 
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