Needing some help with P0171 code (1 Viewer)

[alia176]

I removed the intake hose n looked at it looks good, did a smokers test and no leak I can see, cleaned the MAF last night. Gonna cut the tape on the wiring n inspect it, I will advise what I find,

i like that "smokers" test .

As mentioned previously, your ECU thinks it's running too lean. Meaning either "too much" unmeasured air entering the intake after the MAF sensor. Or, your engine is starving for fuel. Looks like you're on the right track by looking for unmetered/unmeasured (post MAF) air is sneaking into your engine.

Did you check the check valve at the hydro brake vac booster? For that matter, did you check the vac booster to see if it holds vacuum? It's a WAG but might be worth checking.

The myriad of hoses under the intake can get brittle ends. Be sure to replace those PITA hoses or trim the ends. The hoses will feel soft but the ends might be split due to age. Since I run a turbo, I went a little far by applying safety wires to the ends (circled in red) just so they don't pop off after few years.

A P0171 code is set by your vehicle's powertrain control module (PCM) when it detects that the air-to-fuel ratio of your vehicle is too lean. This means that the PCM is relaying that the engine is receiving too much air into the combustion chamber and not enough fuel.

 

[Gunrunner235]

Only 1 landy in Abq at the yard, and it’s been gutted! Lol. Reminds me when they had a 04 Corvette and I went there to get some trim pieces, I got there and it was literally the completely gutted frame and the empty cab,

i like that "smokers" test .

As mentioned previously, your ECU thinks it's running too lean. Meaning either "too much" unmeasured air entering the intake after the MAF sensor. Or, your engine is starving for fuel. Looks like you're on the right track by looking for unmetered/unmeasured (post MAF) air is sneaking into your engine.

Did you check the check valve at the hydro brake vac booster? For that matter, did you check the vac booster to see if it holds vacuum? It's a WAG but might be worth checking.

The myriad of hoses under the intake can get brittle ends. Be sure to replace those PITA hoses or trim the ends. The hoses will feel soft but the ends might be split due to age. Since I run a turbo, I went a little far by applying safety wires to the ends (circled in red) just so they don't pop off after few years.

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A P0171 code is set by your vehicle's powertrain control module (PCM) when it detects that the air-to-fuel ratio of your vehicle is too lean. This means that the PCM is relaying that the engine is receiving too much air into the combustion chamber and not enough fuel.

I did the smoke test. No leaks, which vacuum are u talking about the brake booster? Where is the check valve and should it be pulling a vacuum when at idle?

 

[alia176]

Only 1 landy in Abq at the yard, and it’s been gutted! Lol. Reminds me when they had a 04 Corvette and I went there to get some trim pieces, I got there and it was literally the completely gutted frame and the empty cab,

I did the smoke test. No leaks, which vacuum are u talking about the brake booster? Where is the check valve and should it be pulling a vacuum when at idle?

pls refer to the emission sticker under the hood and I thin it shows you the vac booster. It's the large black round thing on the driver side of the firewall connected to your brake pedal. You might also want to download the FSM for free from this site and study up on the vac system. There are lots of hoses and such as shown on the hood sticker.

For me "landy" usually refers to a LR (land rover). Usually this group uses the term "80" for all things 80 series

 

[landtank]

A P0171 code is set by your vehicle's powertrain control module (PCM) when it detects that the air-to-fuel ratio of your vehicle is too lean. This means that the PCM is relaying that the engine is receiving too much air into the combustion chamber and not enough fuel.

This is not correct. The air to fuel ratio is fine. The engine is NOT RUNNING LEAN!!!

The code indicates that the SYSTEM is lean meaning the system is adding more fuel to reach the proper ratio than what is expected to need on its worse day.

I’d be interested in what the LTFT and STFT numbers are.

14.7 AFR in open loop isn’t normal.

 

[alia176]

This is not correct. The air to fuel ratio is fine. The engine is NOT RUNNING LEAN!!!

The code indicates that the SYSTEM is lean meaning the system is adding more fuel to reach the proper ratio than what is expected to need on its worse day.

I’d be interested in what the LTFT and STFT numbers are.

14.7 AFR in open loop isn’t normal.

Thx for the clarification Rick.

 

[Gunrunner235]

got my new rad in! Finally fought me most of the way, realized my torque wrench was no bueno, ugh, well it’s in, new belts, man I had those cog ones on before and my truck sounds so much smoother now, swapped the fan clutch seems to run good no leaks I could see after running for like 30 mins. LTFT IS 99%, the STFT fluctuates, it was around 14% when I let it idle after installing new parts, it did drop at some points to a negative number, -3 to -1% but pretty constant around the 12 mark, again this was just at idle. What’s should be the average fuel trim?

 

[Gunrunner235]

I will do a short video of the live data I’m getting as far as fuel trim.

 

[landtank]

Is this truck turbo’d?

 

[Gunrunner235]

No. It’s just normal gas motor

 

[Gunrunner235]

So a little update, cleaned the MAF checked again for leaks, cleaned all the contacts on the MAF connector, sprayed around with starter fluid, no revs, did a smoke test, nothing obvious, I did find the PCV grommet was a cheap Chinese POS and torn! Replaced it and ordered a new PCV. While the grommet was torn once I replaced it and cleared the code it came back 7 miles later, I will say tho now my fuel trims are around 3-5% instead of 12-14%, PCV valve I unplugged it with the truck running, no change in motor but it was hissing pulling vacuum, I was under the impression the crankcase pressure opens the valve, does this mean the PCV is no good? I ordered a new one just in case at the dealer but wanted some input on that, anyways, brake booster valve works, so no leak from there. Checked exhaust, still tight and in spec, no cracks or exhaust smell I can see, of course the CAT has been bypassed, o2 sensors look good nothing loose that I can tell all still torqued, I do have a spacer on the rear one, but still looks good. Gonna see if the new PCV does anything n then move on to fuel delivery and then coolant sensor. What are the chances the MAF is bad? Anyway to check it?

 

[Gunrunner235]

so I reset the ECU or PCM, my truck is re-learning, took about 15 mins of driving to get the fuel trims to show up. STFT- between 0-7% at idle, usually negative number while driving, LTFT is at 30% while at idle and around 8% while driving. From my understanding the positive percentage is the amount it’s compensating with fuel to correct lean. But no CEL so far but I do feel it’s coming with 30% at idle. It’s idling pretty erratic, around 600-750, sounds like everytime it tries to drop the idle it stumbles and goes back up, anyways still have a few other things to check, I tested the MAF via video I found, say unplug while running, truck died immediately, said that’s a sign of a working MAF so I’m glad I don’t have to replace that, and I feel the fuel pressure regulator is doing its job by adjusting fuel pressure, gonna do an exhaust test at work with the shop vac, I’ll keep posting until I get it cleared.

 

[landtank]

I would pull the fuel pump out and check the sock.

 

[Gunrunner235]

So….. think I finally found my cause, is a bad intake gasket, the upper to lower. Here is what happened, ordered new silicone hoses, replaced all the hoses, now the trim jumps to 19.5% immediately at idle, levels out to like 1-4% while driving. So got some carb cleaner and started spraying, boom, back near the heater hose it revs! Tried to tighten the bolts, PITA, got a tiny bit of turn on one, but nope didn’t fix the leak. It’s weird that during the smoke test didn’t show any smoke, but I guess running and under vacuum it enough to cause lean code, which is funny bc when the PCV gasket was torn it only trimmed at 7-12%, I guess fix one thing and shows more, plus I had this code 6 months ago, and it went away on its own, well kinda, it just went away when replaced a knock sensor, took 6 months to come back, maybe some gunk plugged it up for a while! anyways, ordering parts, then the tear down begins, any other stuff I should knock out while I have the top off? I already did the fuel filter, I was gonna do the injector seals, and do all the hoses under the upper, valves n VSR. Anything that’s a boat load easier with the upper off? Thanks for all the help guys!

 

[alia176]

So….. think I finally found my cause, is a bad intake gasket, the upper to lower. Here is what happened, ordered new silicone hoses, replaced all the hoses, now the trim jumps to 19.5% immediately at idle, levels out to like 1-4% while driving. So got some carb cleaner and started spraying, boom, back near the heater hose it revs! Tried to tighten the bolts, PITA, got a tiny bit of turn on one, but nope didn’t fix the leak. It’s weird that during the smoke test didn’t show any smoke, but I guess running and under vacuum it enough to cause lean code, which is funny bc when the PCV gasket was torn it only trimmed at 7-12%, I guess fix one thing and shows more, plus I had this code 6 months ago, and it went away on its own, well kinda, it just went away when replaced a knock sensor, took 6 months to come back, maybe some gunk plugged it up for a while! anyways, ordering parts, then the tear down begins, any other stuff I should knock out while I have the top off? I already did the fuel filter, I was gonna do the injector seals, and do all the hoses under the upper, valves n VSR. Anything that’s a boat load easier with the upper off? Thanks for all the help guys!

Congrats amigo!! While you're in there, I'd think about installing a fuel filter pressure sender adapter like I showed in my post above. It'll make future connecting a fuel pressure test kit much easier.

 

[ppc]

Congrats amigo!! While you're in there, I'd think about installing a fuel filter pressure sender adapter like I showed in my post above. It'll make future connecting a fuel pressure test kit much easier.

Can you please provide a link or part number for the fuel pressure sender adapter. The picture of your receipt is not clear enough to pull that information. The picture also shows a barb fitting, not the Schrader valve. Was that a separate purchase?

 

[alia176]

Can you please provide a link or part number for the fuel pressure sender adapter. The picture of your receipt is not clear enough to pull that information. The picture also shows a barb fitting, not the Schrader valve. Was that a separate purchase?

Here you go from my receipt: GS-FA_BANJO-Honda
Glowshift fuel pressure banjo bolt sensor adapter compatible with Honda & Acura installs to fuel filter housig - 90deg thread adapter and copper crush washers.

If you look closely at the first pic, you'll barely make out the Schrader valve pin. I circled it in red! Anyway, this is the piece I grabbed from my fuel pressure testing kit and screwed it onto the 90deg adapter for future connection. It looks like a barb but in reality it is a quick disconnect!