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P0171 and P0174 lean codes

RiCeY

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Try blocking off the purge valve and see if the trims come back down. These are known to fail and introduce unmetered air resulting in a lean condition.
 

Magnum65

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Thanks for your replies.
I've ordered a new MAF sensor... After hearing the price I decided that was enough this time, around $500, shipped from Melbourne and turns up tomorrow. Hope it was the correct choice. Both banks are now permanent codes.
The car seems to run fine, am I correct that the computer system can still manage to deliver enough fuel for >20% long term fuel trim (if fuel system is working correctly) and it's only alerting me to the fact that it's not within the nominal tolerance? Fuel consumption seems to be around the same as before this happened, no rough idle or hesitation and acceleration is normal. If that bloody engine light didn't keep on coming on I wouldn't know there was a problem!

To block off purge valve do I have to remove it or clamp a pipe?
 

greenacc

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Are the MAF's the same on both your cars? If so just swap them and test drive..?
 

RiCeY

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Pull purge valve out of intake manifold 10mm bolt and block the hole at the manifold with tape or something.
 

Magnum65

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OK I swapped the MAF sensor, the flow rate figure increased to >5 but the LTFTRM on both banks increased from around +23% to around +35%! The baro pressure was lower than before but maybe it is today. Also noticed that now increasing revs results in decreasing LTFRTM which is opposite than it was before. Does it take some time to adjust to the new sensor or did I throw away $500?
One other thing the PID reading for purge something on my car is around 20%, my wife's car it's 0.... Mean anything with the purge valve?
Heading off to SA tomorrow so fingers crossed.
 

RiCeY

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Vacuum leak would decrease LTFTs with revs as the higher the revs the less extra air there is so the less fuel compensation is required.
 

mantaray56

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Got some good advice from RiCeY, very knowledgeable and most usually right.
 

Magnum65

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OK, I didn't take my car to SA after all.
Looking at it this morning I did the following:
1. Removed purge valve, placed tape over hole in manifold..... No change
2. Removed brake booster hose and taped.... No change
3. Made smoke box and passed smoke through brake booster hose.... Smoke came out the electric vacuum pump located near the front of the engine but nowhere else. Is this normal as engine is off? Or did the auto electrician swap in a defective secondhand pump?
Don't want to waste anymore money swapping out good components.
Cheers.
 

duca1991

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Hey mate, i have a Z series 2013, i am having the EXACT same issue, both bank 1 and 2.
i noticed a slight drop in idle and it corrects itself. Varies maybe 50rpm then corrects.
this only happens when the A/C is off and the RPM idle is alittle lower.
I am keen to find out what this issue is, I been playing around with my torque PRO app, i am getting over 20% trim on both banks.
 
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