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Discussion Starter #1 (Edited)
so ive been getting an intermittent p0171 and a constant p0411 the 411 is from my sai being removed however im trying to locate the p0171. i was in class yesterday and hooked it up to a snapon solus pro, i had to do global obd2 and the streaming was REAL slow. however i DID get some INCITEFUL information.

was as follows

my long term fuel trim i wanna say was in the range of ~16.4
my short term fuel trim would spike all the way to 24+ and

there would be times when i would legitly be watching the o2 upstream voltage and it would just drop to less than .1v for more than 5-10 seconds resulting in the large spike in the short term fuel trim.

also i believe the the g/s of the maf never really got above 12g/s even near redline and at WOT

im just starting working with live data and when i go in monday i plan to test my fuel pressure as the pump has more than 110000mi on it the second area im going to look into is the exhaust manifold as i did drive around with the cat semi dangling and it got smacked around a little bit. im going to go get my bentley out of my car when i post this but fuel pressure idling hold and running ratings would be nice to get... hopefully the bentley has that info

EDIT: this p0171 started out as a code that would show with a pending status originally when i would delete my p0411 every few months. now it never shows up pending and just comes up bank 1 lean

so this is from the bentley and ill post it for those who may get lead hear via a search

4 cylinders minus the 1.9l and bev and bgd atleast 200 cubic centimeters/30 [email protected] this figure is dependent on voltage. and 29psi at idle 44psi with fpr disconnected and 29psi residual after 10 minutes. this raises the question should i try driving around with my fpr disconnected and the vacuum lines plugged

3,690 Posts
P0171 is a lean code.

Your fuel trims should be under 3.

Do you have freeze frame data associated with the P0171?? If so, post the info.

I would gather your P0171 is being triggered at cruise rather than idle?

Based upon your MAF readings, it really sounds like you MAF is bad and is WAY under reporting.

Gram/sec should be closer to 100 as I recall at WOT? Make sure the tool is actually reading in Gram/sec as well.

But I have also seen MAF's that read close to correct at WOT and idle but are very no linear during cruise and trigger HIGH fuel trims.

Is your MAF OE?

There are a lot of cheap, knock off MAF's rolling around the internet that cause all sorts of problems. Suggest you pony up and buy a quality Siemens/VDO/Bosch MAF from a reputable supplier.

If the MAF is too good of a deal, there is a reason and you likely will not be happy with the end results if you purchase the cheapest thing on the net that you can find.

MAF and O2 sensors are VERY key to fuel supply and should not be purchased on the cheap.

Also verify you engine cooling temps. Likely the engine should be running 205F plus when cruising. It is hard to confirm a soft thermostat once the ambients reach over 70F, but you can cool the radiator with a garden hose to watch the temp behavior if needed.
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