P38 4.0 HSE MAF SENSOR DATA Is it working? Whats wrong? Please help.

Hi there everyone, I hope that you can help me with this.

I have got a 2001 P38 4.0 Range Rover. The problem seems to be with the power output.

As I select drive and accelerate it performs fine on a slow pull away, however when I am doing approx 50 MPH and I want to overtake another vehicle I put my foot to the floor hoping that the gearbox kicks down a few gears. The box selects a lower gear and the revs go up but there is no power coming through the engine. The only thing I get is quite a lot of vibration through the accererator pedal and a delay. The engine revs to 3500rpm plus but the speedometer doesnt really move accept for 2-5 mph more than i was doing.

It feels like the engine is being held back by something. Like the ECU is stopping the engine performing.

There are no lights on in the dash. Now the only codes I'm getting are P0171 System Too Lean Bank 1 &
PO174 System Too Lean Bank 2 which would seem to point to MAF.

I have had it hooked up to a diagnostic and with the live feed coming from the engine it shows that the MAF running Idle is showing as 5.34 g/s and when I up RPM to 2500 its showing 15.20 g/s.

After taking off the MAF sensor and cleaning the wire the idle data now shows as 4.78 g/s. After test driving again since cleaning the sensor I still have the same issue. Nothing has changed.

Can anybody shed any light on the problem and offer any solutions?

Also if anyone has any data that the MAF should be producing that would help to see if it is working correctly.

Many thanks,

Miles

No idea on the MAF readings....but the system also uses data from the Lambdas to set fuelling....

The system measures the incoming air....it gets burnt in the engine....and the lambdas measure the burn efficeny on the way out....

If it is reporting a lean burn, it good be worthwhile looking at the other reporting sensors (the lambdas) that work in conjuction with the MAF to ensure a clean, efficent burn....

I am useless at diagnostics, but if the MAF checks out (start engine then unplug MAF - if the engine note and running changes the MAF is probably OK, if it stays the same the MAF could be duff) the other things to monitor the burn are the Lmabdas and the knock sensors.

Hi,

Thanks for you reply. When I removed the MAF sensor while the engine was running the engine just cut out. So I take it that the MAF is possibly functioning correctly?

Im at a loss coz if the engine is low on power and running lean on bank 1 & 2 why would there not be any dash warning lights on?

I need to get this sorted the quickest and cheapest way. Please help if you can?

thanks

Reset the adaptive values..

Hi Lowfat,

How do I reset the Adaptive Values???

Thanks

That needs to be done using a fullfat diagnostic device like the Nancom Evo(?), the Faultmate Extreme, Autologic, Testbook et al....

Give a good check to the security of all the induction ducting, intake manifold etc....

There could be air leaking into the intake somewhere causing the lean running....

Your initial given figures work out to be about 19.2 KG/hr. I dont think that is far off the ball park in my opinion. My 4.6 drew about 20 KG/hr on tickover. I would look for air leaks to start off with.

4.78g/s = 17.2 Kg/h (20 correct according to RAVE)
15.2g/s = 54.72 Kg/h (60 correct according to RAVE)
+/-3Kg/h is supposed to be acceptable.

The 2,500rpm reading looks in the low side to me, I'd reckon on an air leak downstream of the MAF sensor or the sensor is under-reading. As rewmer said the initial (pre clean) idle reading looked acceptable, after the clean it's still in range - but just. Make sure the plug is pushed firmly home - it sometimes requires a firm shove.

I have similar symptoms to yours I get the 3000RPM and no more power.
Did you check the petrol pump pressure?
some body also mentionned Crankshaft sensor?
Ivan

Is it running on LPG or just petrol?

Miles999 said:

When I removed the MAF sensor while the engine was running the engine just cut out.

Click to expand...

Did you remove or unplug MAF sensor? You should unplug it for this test.

The figures you need to achieve are 22-25kg at idle,90-100kg at 3000rpm in neutral,engine hot all loads off.If the reading goes below 90kg at 3000rpm the engine ecu will not allow a wide enough injector pulse width to get the oxy sensors to switch up rich.Resetting the adaptive values will only mkae matters worse until the Maf is replaced.(If that is what is wrong with it.)
Be careful with aftermarket Maf's if you replace it,I have only recently seen one that actually works properly,most dont.There are very few things that will put the check engine lamp on,the ecu will just default to open loop fuelling when it gets fed up.(Along with poor fuel consumption.)