P38 4.0V8 Thor fault codes P0174&P0171 Help Needed

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Megamagelol1

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Location
Colchester
Good afternoon guys and girls,
I noticed today that my 2001 range rover p38 4.0 thor was fine up until 3000rpm but then really struggled.
got home plugged her in and shes trown up p0174&p0171 codes
now she did fail emission on her mot the other week the first time on lambda's, but the garage managed to get her threw.
im thinking lambdas or MAF?

so ive read the live data and these are my findings:
02 sens DS bank a voltage flickering between 0.443-0.447
bank b static 0.447
Sens US bank a and b both fluctuation a lot between 0.111v and 0.980v very quickly
resistance US 11.77ohms
risistance DS 9.81 ohms
leak factor 0.518
tank pressure 30.99hpa
purge ratio 0.00
purge rate 0.000
purge adaptation -32.00

Load air fixed at -`185.00 kg/h
MAF idle when warm no load 18.5-19kg/h
MAF 3000 rpm no load 70.5kg/h

looking at those figures guys and girls anything jumping out at you?
thanks for your responses in advance
 
Pretty sure the o2 sensors are supposed to seesaw quickly, it's when they stick out get sluggish there's a problem If it runs better without the maf plugged in, that can point to a maf issue Is the air filter good?
What were the mot readings?
 
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P0171 - P0174 fault codes

Hello, I have had this problem for a long time. My 4.0 V8 is strugling at high revs / running flat. The codes that are shown are bank 1 lean and bank 2 lean. I have rest the codes a couple of times. It runs fine after the codes have been reset and then it slowly gets worse by holding back. so...
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kermit_rr said:
Pretty sure the o2 sensors are supposed to seesaw quickly, it's when they stick out get sluggish there's a problem If it runs better without the maf plugged in, that can point to a maf issue Is the air filter good?
What were the mot readings?
Click to expand...
thank you for the reply mate, readings for emmissions were:
lambda fast idle test - limits 0.97-1.03 actual 1.06
second fast idle test limits 0.97-1.03 actual 1.15
everything else was fine.

its the load air that stuck out to me to be fair
i cannt find on RAVE what its ment to be or that was just for NAS cars?
i might take it for a run with the MAF unplugged
i have read you can clean them but am a little apprehensive about that,
thanks again
 
You can clean them with spray, but do not touch them with anything eg finger/screwdriver etc and be 100% sure it's dry before plugging back in
 
right little update ive unplugged MAF took her for a spin and seems loads better revving nice all the way through the rev range.
got home and reset the fuel adaptive values plugged the maf back in and these are my findings: very interesting!
no running lean fault codes this time but these ones::
p0130 and p150 which i believe are 02 sensor codes
however the live data has changed a lot also:
02 sesnor US bank a and b now not changing hardly at all only between 0.124 and 0.133 very very different to earlier
load air has changed from static -185kg/h to fluctuating around 1753kg/h
loop state is open
im at a bit of a loss to be honest is there anyone who could help me out.. thanks very much again
 
Datatek said:
If it runs better with the MAF unplugged that usually means the MAF is duff.
Click to expand...
Hiya mate yeah Im just wondering why it’s now thrown codes back up for 02 sensors, or if the Maf is no good would it show those codes.
I’m going to clean Maf and replace o2 sensors and go from there I think
 
Megamagelol1 said:
Hiya mate yeah Im just wondering why it’s now thrown codes back up for 02 sensors, or if the Maf is no good would it show those codes.
I’m going to clean Maf and replace o2 sensors and go from there I think
Click to expand...
I'd start with just the maf for now and see how you go. If the maf is duff it can't adjust fuel and the lambda codes could be a result of that. 😉
 
Don't junk your old MAF - I cleaned Otto's one very effectively.

Took it out of the trunking and took all the screens / etc off it.
Stood it on the plenum end in a dish, having used cotton wool to plug the 4 exit holes from the actual sensor section.
Carefully filled the sensor tube to the brim with isopropyl alcohol - less than 10ccs.
Left it to soak / evaporate for an hour.
Pulled the cotton wool out carefully, poured a little more isopropyl through without the plugs.
Left it to dry for 30 minutes.
Plugged everything back together, reset adaptives, he worked much better and runs beautifully normally now.
 
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