V8 Range Rover - engine problems.....

[ajmac]

I have a quezzo from my Dad, he is pulling his hair out ATM over the engine problems he is having with his 99MY 4.0 Litre Bosch Motronic V8.

When the engine runs from cold there is no power, rev limit to 3,000rpm etc.... Once up to temperature it is spot on as normal.
He has changed the coolant temp sensor, the throttle pot, disconected the battery to hopefully reset the ECU. All with no result :-(

Fuel pressure rail pressure is fine, under all load conditions.
Diag tool on OBD2 annunciates the fault code for left and right bank lean mixture - no sh*t :-)

He did a compression test yesterday and all are near perfect both wet or dry, about the only things he hasen't changed are the injectors, plugs, leads and coil packs - it's all so expensive!

Any ideas?
Alastair

[Trooper2]

Here are possible causes for code P0171 and P0174:


P0171 - System Too Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The code is set when the adaptive fuel tables reach a rich calibrated limit. Fuel System:
· Contaminated fuel injectors
· Low fuel pressure or running out of fuel (fuel pump, filter, fuel supply line restrictions)
· Vapor recovery system (VMV)
Induction System:
· MAF contamination
· Air leaks between the MAF and throttle body
· Vacuum leaks
· PCV system concern
· Improperly seated engine oil dipstick
EGR System:
· Leaking gasket
· Stuck EGR valve
· Leaking diaphragm or EVR
Base Engine:
· Exhaust leaks before or near the HO2S
· Secondary air concern
Powertrain Control System:
· PCM concern

P0174 - System Too Lean (Bank 2) Same as DTC P0171, but Bank 2. See Possible Causes for DTC P0171

[ajmac]

Thanks,
As far as I know there is no EGR system on the UK spec Rangie as there is no tapping into the exhaust manifold at any point, so that is one off the list.
Evaporative - possible, I naver thought of that....
He is stripping off the inlet manifold plenum this weekend to get at the injectors and have them flow checked at a local specialist. At the same time he has said that he will use a small amount of sealent on all the joints as well as the gaskets, just to be certain of no air leaks post MAF meter.
I will also get him to blank off the breather system for a test drive to see what difference it makes.

Alastair