2003 Montero Limited 3.8L - fuel filter and fuel pressure regulator

RERM

New member
Hi, I'm getting a Code P0171 (Bank 1, System too lean) intermitently on my truck. I've already:

1. Changed O2 sensors (all four) with factory Denso units.

2. Checked and cleaned MAF.

3. Injectors are fine (checked and cleaned).

Now I'm told the fuel filter or the fuel pressure regulator might be to blame for the code. I went to change the fuel filter but when I go to buy it they tell me (both the dealer and the parts places) that I HAVE to buy the $650 fuel pump to get the $40 fuel filter!!!

I find that outrageous!!!

Supposedly Mitsubishi no longer carries the fuel filter by itself!!!

do any of you know of a good aftermarket fuel filter brand I can use (so I don't go through the same ordeal I went through with the O2 sensors from Bosch...)...I've seen Beck Arnley branded filter and fuel pressure regulator, but since my experience with the Bosch aftermarket O2 sensors (they don't work, we HAVE to pony up for the Denso's or were SOL) I'm a little gun shy about aftermarket parts...

Thanks!
 

Inyo_man

Don't piss down my back and tell me it's raining.
I just gave a look on one of the on-line sources for oem parts and found a fuel filter for under $50.00.
If the 3.8L uses the same fuel system as the 3.5L then it should work fine. Check to see if the part number for the fuel pump is the same for the 2002 and the 2003 by calling the parts department at the dealer...if it is, then the fuel filter should drop right in.
Good Luck.

http://oemmitsubishiparts.com/parts...=FUEL SYSTEM COMPONENTS&component=Fuel filter
 

MonteroLTD

Adventurer
Here's a quick copy and paste of this codes description. I have access to Mitchell servce manuals too, if you want I can look up some diagnostic procedures.

Causes
A code P0171 may mean that one or more of the following has happened: The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak downstream of the MAF sensor Possible cracked vacuum or PCV line/connection Faulty or stuck open PCV valve Failed or faulty oxygen sensor (bank 1, sensor 1) Sticking/plugged or failed fuel injector Low fuel pressure (possible plugged/dirty fuel filter!) Exhaust leak between engine and first oxygen sensor

Possible Solutions
A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include: Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling Inspect all vacuum and PCV hoses, replace/repair as required Inspect all hoses and connections in the air intake system Inspect and/or test the intake manifold gaskets for leakage Check for a dirty fuel filter and proper fuel pressure Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool If you have access, you may want to run a smoke test

Read more at: http://www.obd-codes.com/p0171
Copyright © OBD-Codes.com
 

RERM

New member
Well, the problem seems to have been solved by changing the fuel regulator and fuel filter, apparently there's a TSB out for just this situation.....total cost of repairs :

OEM fuel filter and fuel regulator purchased online from RC Hill Mitsubishi (www.mitsubishipartswarehouse.com) for $156.10 and $140 labor...
 

tj90

Member
I know this is an old thread, but Im wondering if this is a clue to my problem. I have an 2003 montero 3.8L. I sometimes have low idle or engine will intermittently loose power instantaneously. Seems like it does it when its cold. Ive had it stall at lights or attempt to stall when the truck is under power. With 270k miles, I am wondering if my filter, pump or regulator need replacing. Ive cleaned and replaced the entire top end (new EGR, vacuum valve body, MAF sensor clean, replaced with used throttle body from junkyard). New wires, plugs, ignition coils.

I think Im going to buy one of those fuel pressure kits from HF and see if there are any clues from that system. Im not sure what its going to tell me. I am wondering if a new fuel pump is just good preventative maintenance at this point?

Any advice is appreciated.
 

Offroadmuch

Explorer
Hello All, I have been away for a while, not spending time on ExPo. Recently my 2003, 3.8L Monty has developed a significant sputter. Maybe starving for fuel? It happens frequently and intermittently, especially after sitting for a day or two. After more driving is goes away almost completely. I am guessing I may need a fuel pump, fuel filter, other stuff? Due to the intermittent occurrence I don’t know if it will show with a fuel line pressure test. Advice? And Thanks
 
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tj90

Member
Hello All, I have been away for a while, not spending time on ExPo. Recently my 2003, 3.8L Monty has developed a significant sputter. Maybe staring for fuel? I happens frequently and intermittently, especially after sitting for a day or two. After more driving is goes away almost completely. I am guessing I may need a fuel pump, fuel filter, other stuff? Due to the intermittent occurrence I don’t know if it will show with a fuel line pressure test. Advice? And Thanks

THis sounds like my problem too....
 

tj90

Member
i have no codes. ive been monitoring real time data when it happens. I dont see anything abnormal - maybe im looking at the wrong monitors but nothing abnormal. i do notice that my vacuum maxes out at 13. Ive read that low vacuum that slowly goes up (toward zero) indicates blocked cats. Ill ask you guys about this on another thread. I bought a fuel pressure gage but it failed shortly after hooking it up on my truck. I did not get a chance to drive it around. At idle, my fuel was reading 60 psi. Do not buy the master fuel injector kit from harbor freight. Absolute junk... The rubber swells with gasoline and renders the kit useless. Anyway, Im thinking it may take more diagnosis with another fuel gage but Im leaning toward transmission now. Im going to drive it in tiptronic mode and see if its limited to a particular gear.
 

Offroadmuch

Explorer
Mine is almost undrivable now. RPM’s want to stay low and then it stalls. If I push the gas and brake I can get it up to a drivable speed. I am going to buy a Denso fuel pump and Mitsubishi fuel filter assembly a nd take it to my guy. I will get codes read and his opinion and go from there.
 

Michael Brown

You followed me, so now we're both lost
Also check for vacuum leaks in the hoses. A vacuum leak will cause low engine speed on the 3.5L. It may also happen on the 3.8L.

Is there any engine oil leaking into the cylinders while sitting?
 

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