Mechanics

TROUBLE CODES P0171, P0174 HELP!

Ford Explorer

I have a 1996 Ford Explorer 2WD 5.0 EFI with 205000 miles on it. I have 2 trouble codes displayed I retrieved P0171 and P0174. They are Lean bank 1 and Lean bank 2. Symptions are it is difficult to start cold in morning it has to be cranked over a few times before it fires up. When it is warm it starts easier. Idle is fairly smooth for a motors with this many miles. I replaced the vacuum hoses and PVC valve reset the light and it came back on after I cycled the engine the appropriate number of times. I also used some MAF cleaner and sprayed in the port where the sensor is located in the throttle body. I don't know where to go from here I don't want to start changing parts because that gets expense quick. I need the steps to trouble shoot these codes the chilton manuel does not have that kind of help.
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Wrprlp
November 2, 2006.



The trouble codes are no going to definetly tell you what is wrong but will give you a direction to go in. The lean bank could mean a few things so start with the most likely and least exspensive. Have you recently cleaned the fuel injectors. For a few dollars you can purchase a bottle of fuel injector cleaner. If this is the problem if will probably take a few bottles and tank full of gas before if works. While you are at it change the fuel filter. It could be clogged and causing a restriction in the fuel line. If the problem still exist next check that the fuel pump is suppling the proper pressure with a fuel pressure tester. If you don't have one maybe you can borrow one. Make sure the readings are with in specs for the car. If not in specs you may have a kink in the line or the pump may need replacing. If this doesn't fix the problem I would next suspect the o2 senors are fautly.( Due to the mileage and symtoms. Where they ever replaced?) If you have a repair manual they will sometimes explain how to test them for your particular car. Since money is a issue you may want to replace only one first and rescan for codes to see if the bank you change has been corrected. Hope this helps Good luck Backyardmechanic : o
PS make sure you clear the codes after each attempt to repair so you will know if you got it. It sounds like maybe your O2 sensors are bad. If they have failed, it will disturb the air fuel ratio and on the 5.0 if I'm not mistaken, it has a mid pipe with two banks, the left and right, which would be causing the computer to lean out the mixture.

Tiny
Backyardmechanic
Dec 4, 2006.
I have the same lean conition that wont go away.I replaced the 02 sensors put in a new fuel pump replaced the filter. Still get the lean code. My truck runs fine except idles rourgh sometimes. If anyone tells you to replace the 02 sensors they dont know what there talking about. Ask them how to check them first. Dont waste the mony.

Tiny
Timl
Jul 4, 2007.
Its the Mass Airflow Sensor, when both banks have the same probleem it can only be a few things. Fords have a bit of a problem with them

Tiny
Jack42
Oct 3, 2007.
I have a 1997 Ford Explorer 4.0L pushrod (x on VIN) automatic 4x4 with almost 159, 000 miles. The vehicle started running rough with poor acceleration/power last winter. The only maintenance to the engined performed since I bought the vehicle with 42,000 miles has been limited to oil and filter changes, new spark plugs and wires (changed last week with Ford parts), and an alternator.

Today I rented a code scanner and obtained the following codes from my Explorer. P0171 (System Too Lean (Bank 1)); P0174 (System Too Lean (Bank 2)); P0301 (Cylinder 1 Misfire Detected); P0401 (Exhaust Gas Recirculation Flow Insufficient Detected). I have read from this thread and my Haynes manual that P0171, P0174 and possibly P0401 may be attributed to a faulty MAF sensor, but I am not sure about the misfire in cylinder 1 (P0301) code. I also had a pending code (P0153(O2 Circuit Slow Response (Bank 2, Sensor 1)), but it disappeared after driving the vehicle for 28 miles and immediately scanning again while the engine was warm.

In the morning I'll swap the plugs and wires of cylinders 1 and 2 and see if the P0301 code changes to P0302. I did buy a bottle of Valvoline complete fuel system cleaner last week and added it to a full tank, but have only gone through a little more than half of the tank of gas. If a fuel injector is fouled, perhaps it may take longer to clean.

Any advice by an expert as to what is most likely the problem and what steps I should take to correct it would be appreciated, as my wife cannot drive our Explore until I can get it to pass emmisions testing and re-register it.

Thanks from Alaska!

Tiny
Alaska Miner
Nov 3, 2007.
The cyl misfire could be it needing a tune up. The lean bk1 and 2 codes. Check for any vacuum leaks in a common area for both sides of the engine (throttle body, major vacuum ports, pcv line) if none are found, I would suspect the MAF, Fords have a problem with them, and I wouldnt use an aftermarket one, havent personally had any luck with them, more driveability issues. The slow o2 sensor code might be from the MAF as well, if one isnt responding as fast as the other for mixture adjustment, a code will be set. The EGR code. Try manually activating the EGR valve with a vcuum pump with engine at idle. Should almost if not completely kill the engine, if it doesnt the passages are plugged and will need to be cleaned. If stumbles, then I would replace the DPFE (differnetial pressure feedback sensor) It measures the backpressure in the exhaust system, see them fail often

Tiny
Jack42
Nov 3, 2007.
You either have a good size vacuum leak or a bad MAF.
Look around and listen for a vacuum leak. You can take a 3 foot piece of rubber hose.3/8 or bigger will work and hold one end in your ear. Move the other end around the vacuum lines and hoses. You will hear a vacuum leak pretty easily.
You can also spray carb cleaner around lines and gaskets.A change in idle indicates a leak where the cleaner is getting into plenum.
MAF can be cleaned. The explore should have the MAF that has the aluminum snorle tube and the actual MAF sensor has three anti tamper torx screws holding it in. I think they are t-15s. But they are the anit tamper ones.
You can get them out with a little work without the right torx bit.A small flat head screwdriver will work. I have also used a dremmel cut off tool to cut a slight slot in the heads of them so I can use a flat blade screw driver. When I have misplaced my anti tamper torxs and in a hurry.
Take it out and spray the two little wires with the resistor looking thingys (technical aren't I) with brake parts cleaner or Mass airflow intake cleaner. Either will work fine.
You can use a q-tip on them too but BE CAREFUL. If you bend them too much or break the connection. You will most likely be buying a new one. Unless you are real handy with a fine tip soldering iron.
Put it back together an clear codes and drive it.
Find those vacuum leaks too.

Tiny
TobyU
Nov 16, 2007.
Cant remember the last time I saw tampre-resistant torx on a MAF on a Ford. What great ideas though. Wish I had said the same thing.

Tiny
Jack42
Nov 17, 2007.