The Dreaded P0171

[Mooseman]

Hey no problem, the more info the better.

Definitely replace your FPR. And the MAP is cheap enough to just replace it as well.

Did you thoroughly check your exhaust manifold for cracks and/or missing bolts? A leak there can also give a false lean code because it can also suck some air in through cracks.

 

[ghost.leader07]

Hey no problem, the more info the better.

Definitely replace your FPR. And the MAP is cheap enough to just replace it as well.

Did you thoroughly check your exhaust manifold for cracks and/or missing bolts? A leak there can also give a false lean code because it can also suck some air in through cracks.

Thanks for quick response, I'll order both of them tonight... About the exhaust manifold I'll check although it sounds like a difficult one... I've replaced my CAT not long ago and I'm not quite sure about the welding i suspect a leak there but could it cause a lean code?

 

[Mooseman]

Welds at the cat wouldn't affect the upstream O2 sensor. Try to look with a mirror, your phone using video, from under. The usual suspect places are the rear 3 ports for cracks along the back of the manifold.

 

[ghost.leader07]

Welds at the cat wouldn't affect the upstream O2 sensor. Try to look with a mirror, your phone using video, from under. The usual suspect places are the rear 3 ports for cracks along the back of the manifold.

Is it possible to check the exhaust manifold without removing the shroud?

 

[Mooseman]

You can try looking at the backside first but it can crack on either side.

 

[ghost.leader07]

You can try looking at the backside first but it can crack on either side.

Sorry I've been busy the last couple of days and didn't get around to check on it until today... So I've checked exhaust manifold and i can confirm it's in one piece so i'm thinking it could be a fuel problem or a sensor something like MAP sensor which i'm still on waiting on to arrive however there's something that has been bugging me about the fuel pressure regulator which after disconnecting it and capping off its vacuum line on the resonator side and i found no difference in terms of performance ( i was able to drive at 95 mph) no problems! is it possible that the FPR is stuck wide open allowing fuel to go through? what about the vacuum line? i mean it doesn't serve a purpose in my case... there's no obvious leaks from the FPR but i can smell gas from the vacuum port if i did a suction on it, is it supposed to do that? nothing happens if i blow in it it's pretty closed.. should it push air in or suck air out?

Sorry for these questions but answering them will help me determine the condition of my FPR because i hate replacing parts that aren't defective

Any help is greatly appreciated.

 

[Mooseman]

You can confirm if the FPR is having issues is by checking the actual fuel pressure. If the fuel pressure is low, it could cause a lean condition. I think the line is a "just in case" it leaks so it will go into the resonator box to get burned instead of leaking all over the engine and possibly cause a fire. I have a similar FPR on my snowmobile and that hose is connected to nothing.

I know you smoke tested it but I would still do a check using carb cleaner. Sometimes there could be a leak that won't allow low pressure smoke out but allow high vacuum in. I think air is getting in there somewhere.

 

[NJTB]

Another thing you MAY want to try is bringing it to a dealer and have all the latest PCM updates flashed into it. If you've never done it, could be a home run.

 

[ghost.leader07]

You can confirm if the FPR is having issues is by checking the actual fuel pressure. If the fuel pressure is low, it could cause a lean condition. I think the line is a "just in case" it leaks so it will go into the resonator box to get burned instead of leaking all over the engine and possibly cause a fire. I have a similar FPR on my snowmobile and that hose is connected to nothing.

I know you smoke tested it but I would still do a check using carb cleaner. Sometimes there could be a leak that won't allow low pressure smoke out but allow high vacuum in. I think air is getting in there somewhere.

Just finished doing a fuel pressure test and here's what i gathered:

1- After hooking the pressure gauge the fuel pressure reads at 52 psi (car is off no keys in the ignition)
2- as soon as i turning the key to on position the fuel pressure jumps to 55 psi then drops 52 psi immediately it happens while to the pump priming up)
3- when turn the engine on and letting it idle the fuel pressure reads at about 55 psi

Based on my little research the optimal fuel pressure should be between 50-57 psi so I think my fuel pressure is good?

P.S. when pulling off the vacuum hose off the FPR nothing happened no change in the idle or fuel pressure... Could this indicate that there's something wrong with fuel pressure regulator since it doesn't do anything even while driving with vacuum hose unplugged? Could be stuck open or closed?

[UPDATE] I did another fuel pressure test to verify my pump when primed holds pressure at 51 psi for a while but the pressure start to drop after 15 minutes or so but it's slow and if I remove my keys and leave it for like an hour my fuel pressure drops to 30 psi and continue to drop but it's quite slow...is that normal? I don't have trouble starting the car... Could it be the the FPR? I have replaced the fuel filter a while ago and i have a poor fuel economy.

 

[gica]

Did you ever get this fixed? I have identical issues with my 2004. Thanks in advance.