dang po174 code

[Wray-Wray]

1999 Mercury Mountaineer
5.0 AWD
mods
K&N filter(has been the truck for 30k)
E3 Diamond fire plugs(been in for 10k)
JBL 9mm racing wires(been in for 10k)
True 2.25in Dual cherry bomb(straight threw red) mufflers (8k)
B&M Stage 2 street strip shift kit(15k)
fuel filter(been 15k)

ok i have search this site but i didn't find a solution for my exact symptoms....



only code po174- bank 2 running lean.....


in the 3000-5000rpm range (with its floored) i have rough acceleration.....like it has no fuel....the truck will not do this every time you floor it....it is random

it makes a hissing sound when running like every other day BUT ONLY after it hits running temp.....After about 10 miles on the highway....if you shut it down it will hiss loudly....


it makes a hissing sound when running like every other day BUT ONLY after it hits running temp.....After about 10 miles on the highway....if you shut it down it will hiss loudly....

when i run octane boosters in it or injector cleaner, it will not have random rough acceleration although hissing continues...

it has been doing this for the past, i'd say 3000miles maybe about 4 months time... and just 2 days ago my check engine light came on and i took it in and got the code so i bought injector cleaner filled it up.....dumped it in and cleared the computer

then i filled it up again yesterday and put octane booster in and it did it just once

anyone one with any ideas.....


My train of thought is this...

Can't be MAF because both banks should be lean not just one.....

can't be an O2 sensor because my gas mileage would be crappy....but it has not changed....and its the part thats telling me my bank 2 is running lean

Fuel filter is less then 20k old and i run injector cleaner threw the system regularly (every few tanks) plus my fuel pressure is in spec, although there seemed to be an air bubble in my fuel rail. When I checked my fuel pressure. i havent run my truck outta gas ever......although my wife my have and just not told me.....

EGR differential pressure sensor- can't be that because it should also effect both banks



any idea's???


thanks in advance

 

[Wray-Wray]

bump....help please....im at a loss here

 

[jremington59]

http://www.obd-codes.com/p0174

It could be just the MAF sensor. It's worth cleaning it anyways.

 

[Wray-Wray]

i'll try it tommrow....i guess it couldn't hurt right?...i mean the K&N filter has been in for a while...the MAF sensor could b dirty

 

[Wray-Wray]

interesting development.....

I had cleared my computer when I was at auto zone, and ran the injector cleaner n stuff threw it. Now on my way to advanced auto to grab sum MAFS cleaner. My check engine light came on.

So I rolled up got the code reader and scanned it. It read "Po171-bank 1 to lean". So I was like "are you fricken kidding me."

There was no other codes. So I cleared the computer again, got me some MAFS cleaner and went to town. Let it dry for like 30min. My rug rats were playing with the wife on the play ground near by. Started her up.

Now it has a rough idol some of the time, but it always has a smooth ride. Up the power band.

i don't get it wtf? Why would it say bank 2 lean then a week later say only bank 1 is lean?

 

[Turdle]

I think you have a vacuum leak. You mentioned hissing. Have you checked the PCV hose? There is a grommet where it enters the intake manifold, way back at the center of the lower intake. This can develop a leak. There are several other areas to check for vacuum leaks, but this is the first place I would look.



It's a bugger to get back there to it, but you can from the driver side.

 

[Wray-Wray]

so what do i do grab a new hose and grommet? and is that the line that comes off the brake booster?

is that like just pull it out and, plug the new one in type deal?

 

[Turdle]

yes if the old one feels loose. The grommet is what develops the leak. It pops into the hole in the intake, then you plug the PCV vale into it.



The OCV vacuum lines come from under the driver side of the upper plennum. You will feel a "t" down there with several 1/2" hoses. one of them goes all the way back to the PCV.

 

[asafley]

As said in the previous posts, the pcv valve might be at fault here. My Plastic T had a small crack in it and it was enough to throw the check engine light but not both the P0171 and P0174 at the time. I could not find a replacement for the T fitting, so I went to lowe's and bought 2 feet of air hose and a T fitting. Replaced the T and hoses on the truck with a new design. Hose from the pcv valve to the T fittings and from the T fittings to the two ports on the left and right air intake manifold. It has been several months now and 5000 Miles with no problems or a check engine light. Hope that helps.

 

[Wray-Wray]

i cleaned my MAFS again and everything is gud now....if it starts up again i will go to my vacuum lines first this time....

 

[Wray-Wray]

the hissing turned out to be my AC compressor..... if i have the AC on and shut it off the truck hisses....if i don't have my AC on it doesn't hiss at all

 

[Wray-Wray]

thank you guys for all the help!

 

[joe doe]

As said in the previous posts, the pcv valve might be at fault here. My Plastic T had a small crack in it and it was enough to throw the check engine light but not both the P0171 and P0174 at the time. I could not find a replacement for the T fitting, so I went to lowe's and bought 2 feet of air hose and a T fitting. Replaced the T and hoses on the truck with a new design. Hose from the pcv valve to the T fittings and from the T fittings to the two ports on the left and right air intake manifold. It has been several months now and 5000 Miles with no problems or a check engine light. Hope that helps.

this is common on the 5.0 engine .if this is not your fix then you have a leaky intake,or leaking upper plenum orings.resetting the computer will not fix your problem.
you will be back.