Hi Guy's,

Pulled a code of P0171. Lean on Bank #1. P0174 Lean on bank #2. It said check the following:

MAF SENSOR- Not sure how to test it. I pulled it and looked inside and cleaned it w/ electrical cleaner. However it looked like new when I pulled it. No dirt at all.

Vacuum leak- Did not detect one. checked all lines into the plenum, around the throttle body. all connected and no tears. Unless, a pinhole size leak would cause the codes.

Fuel Pressure, Fuel Filter>>>>> Please read very bottom.

PVC and Air filter have been replaced. PVC hose appears to be fine.

History......Back in July I gave the car a tune-up. New Plugs, Wires and Cap & Rotor. I changed the Valve cover Gaskets and the Plenum Gasket. I Had to changed some of the O-rings on my F. Injectors. I put everything back together and still had a leak at one of the F. Injectors. Replaced that O-Ring also.

*Important Part*
I didn't want to put the Plenum and Throttle Body back on w/o testing for a fuel leak at the Injectors. So, I decidec to test the car for leaks and started it. I let it run for 5 seconds W/O the Plenum and Throttle Body attached. No gas coming out of the F.Injectors put everything back together and started driving the car and it ran great! 10 min. into driving the service engine light came on. I didn't have much concern because the car ran great! For the last several months it was going on and off. About a month ago it has stayed on steady. So, after 6 months I finally pulled the code at Autozone and the code is the P0171/P0174. The weird thing it purrs like a kitten. Probably killing my fuel economy. I haven't noticed too much decline in gas milage.


Fuel Filter>>>> The filter has never been changed since I owned the car. 36,000m now has 80,000m I'm assuming it's original seeing evrything else I have done on the cars has not been change out at the regular service intervals. I've been real hessitant to touch the filter because the nut is rusted around the filter. I do plan on tackling this project this weekend.

Is it really possible the cars Fuel Filter could cause the codes? Any help on how to test the MAF Sensor would be great! The car runs great...... I don't get it?

Any suggestion would be great.

P.S. no mention in any research about a possible bad O2 sensor. Code doesn't even point to that either.

 

[QUOTE=ryan51173;267416]Hi Guy's,

Pulled a code of P0171. Lean on Bank #1. P0174 Lean on bank #2. It said check the following:

MAF SENSOR- Not sure how to test it. I pulled it and looked inside and cleaned it w/ electrical cleaner. However it looked like new when I pulled it. No dirt at all.
...

possible causes/influences...
fuel pump,
fuel filter.
oxygen sensor,
fuel pressure regulator,
maf sensor,
iat sensor,
vacum leak.
TESTING
1. Relieve fuel system pressure.
2. Disconnecthe battery negative cable.
3. Disconnecth e fuel hrgh pressureh osea t the
delivery pipe side.
Observe all applicable safety precautions
when working around fuel. Whenever servicing
the fuel system, always work in a well
ventilated area. Do not allow fuel spray or
vapors to come in contact with a spark or
open flame. Keep a dry chemical fire extinguisher
near the work area. Always keep fuel
in a container specifically designed for fuel
storage; also, always properly seal fuel containers
to avoid the possibility of fire or exalosion.
4. Connect a fuel pressure gauge to tools
MD998709 and MD998742 or exacte quivalent,w ith
appropriatea dapters,s ealsa nd/or gasketst o prevent
leaks during the test. Install the gauge and adapter
betweenth e delivery pipe and high pressureh ose.I nstall
carefully to prevent leaks.
5. Connect the negative battery cable.
6. Apply battery voltage to the terminal for fuel
pump activation (located in the engine compartment)
to run the fuel pump, and check for leaks.
7. Start the engine and run at curb idle speed.
8. Measure the fuel pressure and compare to
the specifications listed in the chart in Section 1.
9. Locate and disconnect the vacuum hose running
to the fuel pressure regulator. Plug the end of
the hose and record the fuel pressure again. The fuel
pressure should have increased approximately IO
psi.
10. Reconnectth e vacuumh oset he fuel pressure
regulator. After the fuel pressure stabilizes, race the
engine 2-3 times and check that the fuel pressure
does not fall when the engine is running at idle.
il. Check to be sure there is fuel pressure in the
return hose by gently pressing the fuel return hose
with fingers while racing the engine. There will be no
fuel pressure in the return hose when the volume of
fuel flow is low.
12. If fuel pressure is too low, check for a
clogged fuel filter, a defective fuel pressure regulator
or a defective fuel pump, any of which will require replacement.
13. If fuel pressure is too high, the fuel pressure
regulator is defective and will have to be replaced or
the fuel return is bent or clogged. If the fuel pressure
readmg does not change when the vacuum hose is
disconnectedt,h e hose is cloggedo r the valve is
stuck in the fuel pressure regulator and it will have to
be replaced.
14. Stop the engine and check for changes in the
fuel pressure gauge. It should not drop. If the gauge
reading does drop, watch the rate of drop. If fuel
pressure drops slowly, the likely cause is a leaking
injectorw hich will requirer eplacementI.f the fuel
pressure drops immediately after the engine is
stopped, the check valve in the fuel pump isn’t closing
and the fuel pump will have to be replaced.
15. Relieve fuel system pressure.
16. Disconnecth e high pressureh osea nd remove
the fuel pressure gauge from the delivery pipe.
17. Install a new O-ring in the groove of the high
pressure hose. Connect the hose to the delivery pipe
and tighten the screws. After Installation, apply battery
voltage to the terminal for fuel pump activation to
run the fuel pump. Check for leaks.

MAF sensor testing...
http://i602.photobucket.com/albums/t...sortesting.jpg

Additionally, the OBD-II system employs adaptive
fuel logic. This processi s usedt o compensatefo r
normal wear and variability within the fuel system.
Oncet he enginee nterss teady-stateo peration,t he
control module watches the oxygen sensor signal for
a bias or tendency to run slightly rich or lean. If such
a bias is detectedt,h e adaptivel ogic correctst he fuel
delivery to bring the air/fuel mixture towards a centeredo
r 14.7:1 ratio. This compensatings hift is
stored In a non-volatile memory which is retained by
battery power even with the ignition switched OFF.
The correction factor is then available the next time
the vehicle is operated

all info direct from service manual as per my post in forum (download link) very handy for fault analysis and saving cash

Snoops

 

007Snoopy

Thanks for all the great detailed info. I think I'm going to start testing all the sensors, as I have located test procedures for the each sensors in my manual. If proven to be good.........I will probably have my mechanic do the fuel/vacuum testing that you mentioned. I'll post what I fined to help others out. Hopefully it's sooner than later. So, thanks again for the quick response.


-Ryan

 

Problem fixed! I found a vacuum line disconnected from my Plenum.


Thanks!

 

Well done buddy

Snoops