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1995-2002 Range Rover P38A
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121 Posts
Discussion Starter · #1 ·
Getting pending codes P0174, P0171, P0130 & P0154. (Lean trim and O2 Sensor). Also ever since I've had the car it has misfired / vibrated at full throttle and high RPM. Using torque I can see the O2 sensors working fine, but the other day I managed to catch it misbehaving. Flooring it up a fairly steep hill the mixture went rich (as you would expect) and then after a few seconds the sensor voltages started to drop slowly to almost zero and then stayed there. After lifting off (to protect the engine) the O2 sensors returned to cycling after a couple of seconds.
Looks like fuel starvation at high flow rates. I'm going to check the fuel pressure to confirm. Obviously the fuel pump would be suspect but googling seems to suggest they either work or they don't - couldn't find a case of low flow output. A partial blockage would also give the same symptoms. Mine is a Thor with the PRV in the pump so there is no return line to check the flow in and it is a tremendous pain to get at the pump and fuel line to check them (tank out or cut holes / remove upper manifold and coils).
Has anybody come across a similar issue and what did it turn out to be?
 

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1995-2002 Range Rover P38A
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772 Posts
I had a misfire on my Thor, I went down the line of pump, coils and leads, turned out to be throttle position sensor, worth a check, but don't buy a cheap Chinese one, they don't work ..
 

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1995-2002 Range Rover P38A
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121 Posts
Discussion Starter · #3 ·
Put a gauge on it today but in the meantime I had filled the tank - Guess what - doesn't run lean now! I'll check again when the tank is lower but starting to look like a partial blockage to me. Oh joy I'm really looking forward to taking the tank out!
 

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1995-2002 Range Rover P38A
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My long time problem was the intake was not bolted down. It was missing the bolt in the back. Once I replaced it no more lean. It was sucking in too much air obviously...

Same symptoms as yours. Going up a hill too much air. Pulling a load, too much air.
 
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