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Discussion Starter · #1 ·
Perhaps someone can point me in the right direction. I have an 05' LR3 SE, I am trying to pass smog but am getting P0171 and P0174 codes. I have cleaned MAF, ran two cans of Sea Foam in the last 4 full tanks, cleaned the throttle body and replaced a stuck open PCV valve. When driving after clearing the codes (100 miles city and highway) i only get pending codes. However, when I park and test at idle, 1500 RPM and 2500 RPM the light comes back on. At idle the LTFT is -1.8, -.8 STFT 1.1, 1.0, at 1500 RPM LFTF .8, 0 STFT 0, .8, but at 2500 RPM LTFT 12.2, 10.8 STFT -10.0, -10.2. I have done a smoke test and nothing comes up. Could it possibly be a small intake leak? Has anyone solved this problem?
 

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Major vacuum leak!
Line off etc. Get the plastic cover off and have a good look around. If you still don't see it you will likely hear a sucking sound while the engine is running
1500-2500 rpm you can't leave it and should not drive around like that!
 

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Discussion Starter · #3 ·
Thanks for your input.

Thank you for your replies. I have cleared the codes several times and it seems my issue is while parked. When I drive the Long Term and Short Term fuel trims are right around zero, and when I'm idling at a stop the LTFT is between 2-3 and the STFT is between -0.8 and 0.8. After driving a couple of drive cycles I only get pending codes. However, when I am parked and rev the engine it is zeroed out at idle and 1500 RPM but goes up when I hold it at 2500 RPM and the CEL comes back on. I did a smoke test and only found a small leak at the oil filler neck so I replaced it and did another smoke check and found nothing. When the engine is at idle I can't really hear any leaks but when I turn it off I hear a loud sucking sound. Could it be the intake manifold has a small leak? I am not driving the vehicle other than trying to find the problem but I need to fix it so I can pass smog.
 

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Off the top of my head 171 and 174 are lean conditions on both banks. which means the problem is probably before the intake manifold. Rt after the maf sensor is a plastic shroud box that the o ring clamps hold on to and the plastic/metal rings underneath crack and let air in. You need to take apart and inspect. That is if it's a 4.4 jag motor? If you have no cracks under the o ring clamps and you can't hear a leak then you could have a bad maf sensor. Whenever I clean a maf that never works! It's always the internal part of the sensor that is bad. The last time I saw 171 and 174 It was the cracks in the plastic intake box before it attaches to motor that was the problem. Super small cracks which are hard to see when you take apart or smoke it. I have also seen those two codes pop and it was a bad maf and cleaning never works you have to change sensor. The codes are for both sides of the motor having a lean condition and that is unlikely, so u have to pin point the top of the motor first before the air is split up into the intake cylinders. For example you never have two o2 sensors go bad on different banks at the same time if truck is running good. If you had a large leak then you would have a rough idle or misfire so I don't think that ur problem. Its the cracks or prob bad maf hope this helps. Ck for cracks first then change maf
 
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