Code P0174!!!!!! Chime in people...

[96Greenster]

Well yes another code thread, Im getting a constant P0174 code(lean bank 2). Ive erase it a few times, but then pops right back up. Ive tried cleaning the maf sensor, but didnt help, BTW the truck runs smooth witout hesitation etc... What are the most common causes for this particular code???

Its a 99 4.0L 4x4 auto...Thanx in advance

 

[Big Jim M]

Vacuume leaks are common causes for this problem. check all hoses and all gaskets.. I use a propane tank with a four foot long hose on it. I turn the propane on and while the engine is idleing I put the end of the hose all around where there could be a leak. When the engine revs or smoothes out there is the leak.
Big JIm

 

[96Greenster]

Vacuume leaks are common causes for this problem. check all hoses and all gaskets.. I use a propane tank with a four foot long hose on it. I turn the propane on and while the engine is idleing I put the end of the hose all around where there could be a leak. When the engine revs or smoothes out there is the leak.
Big JIm

Should be a vacumme leak some where then?? I disassemble the intake once before and didnt see any bad vacumme lines...

 

[SMTGREG]

If its only code p0174 it could be a bad oxygen sensor. If possible swap the oxygen sensors from side to side and see if the code changes to p0172. If it does the sensor is bad.

 

[96Greenster]

I believe its P0171 aint it? And yeah its only that code... Its kinda weird I got both P0174 & P0171 one time, but now days I get 174 only... I check out the O2 sensor, Thanx

 

[Hotrodlincoln]

Might be an exhaust leak before the sensor. A leak will let exhaust out and air in. Air in the exhaust will read as a lean mixture.

 

[96Greenster]

Might be an exhaust leak before the sensor. A leak will let exhaust out and air in. Air in the exhaust will read as a lean mixture.

I thought that too but I dont hear a leak or see cracks on manifold or pipe

 

[DennisF]

I had both the P0171 and P0174 codes. It seemed to run fine, but one day while I was washing the engine, which I leave running while doing so. I noticed the water was getting sucked into the intake manifold where the fuel rail meets the plastic spacer. About a month later, I replaced the rubber gasket on the upper portion of the intake manifold and the problem was gone and hasn't recurred for more than three years.

Replacing the intake manifold gasket is not difficult, but you'll need a variety of tools to reach all the bolts.

Good Luck!

 

[rfingon]

I have been getting the P0171 and P0174 codes on a regular basis now myself. Always resetting the CEL, and it will come back within two drives of my truck. I replaced all three sensors 1.5 years ago when I first got both codes. I figured that it wouldn't be a bad idea to replace the O2 sensors, since I bought the '98 Ranger XLT 4.0L with 102K on it. This did not alleviate the problem. Also, I did inspect the PCV rubber hose (seemed tight) and pulled out the PCV valve (which did rattle, but I did not run any solvent through it--definitely should have). This winter, I drove it to WI from CA. It was freaking cold in WI (I am talking single digits), and everyday I drove it, I got both codes. Bought some MAF sensor cleaner, took the MAF sensor out and cleaned it (BTW, I deem you insane for using a toothbrush on it, this is a $130 part to replace and is a delicate part). Back in CA, did not get the code anymore.

So in May, I regularly get the code again. I also have this crazy howling occasionally now from under the hood that goes away when I turn off the AC. I decide to pull the trigger and replace the MAF sensor. Basically threw away $130. Valve cover gaskets look OK and are not leaking to my knowledge. Hose clamps tight. I am going to replace the PCV rubber hose, PCV valve and valve cover grommet outright now. I definitely need to investigate the intake manifold gasket however. It would be awesome to get rid of these freakin' codes!

 

[Black_Splash]

I'd also check vacuum hoses. There is one that makes a 90 degree bend on the left front that breaks. You might have to move the radiator hose to see it.

 

[floridaoranges]

I'd also check vacuum hoses. There is one that makes a 90 degree bend on the left front that breaks. You might have to move the radiator hose to see it.

Thats exactly what mine was, I replaced it with a plastic heater hose elbow and haven't had those codes since.

 

[rfingon]

Sorry for the belated reply. Today I did the propane on a four foot tube stick trick and went all around the plenum (fuel rail, seams, all that). No indication of an air leak on the plastic intake. So when you say vacuum line on the front left, I am assuming that this direction is when you are standing in front of the truck and not behind the steering wheel (although one should not assume). I do see a 90 degree elbow in the 3/8" ID vacuum line. Is this the elbow that you refer to (the one with the long plastic tab on the elbow)? Upon wiggling, this seems fairly loosey goosey (and not snug, as I would expect), so tomorrow I will replace all lengths of this 3/8" ID tubing. The short 3/8" ID piece seems dry rotted on the outside.

Back to the replaced MAF sensor. The howling noise emanates from here or immediately below in the air filter compartment. This howling noise was the same when the old MAF sensor was in place. I had previously checked the voltage readings per Chilton's manual prior to replacing the MAF sensor, and all of this seemed within Chilton's spec. The howling noise is in the note of D4. How do I know this? IPhone voice recorder > online tuner. If unsure of D4 note, go to any search engine and type "D4 note sound sample". If anyone could provide the meaning (or shed any light whatsoever) of this howling noise, I would greatly appreciate it. Thanks in advance.

Hopefully, that noise will go away after I replace the thick diameter vacuum line. I will keep you posted.

 

[4x4 Ranger]

This Worked For Me

I Got both 171 and 174 codes on my 2001 Ranger 4x4 XLT 4.0. An all i had to do was get the PCV valve changed out. No Codes Since.

 

[rfingon]

I have replaced the PCV valve already. The vacuum hose looks OK and is tight going into both the intake and the valve cover. Valve cover grommet looks fine too. My propane hose test did not detect anything here either. I am pretty confident that this is not the cause of my codes. I wish it were. I still have yet to go into town today to get a new vacuum line for the 90° elbow bend. That will happen later today.

 

[rfingon]

The vacuum hoses definitely needed to be replaced, as both were dry rotted. The outsides of both hoses were basically shedding off onto my nitrile gloves. Unfortunately, replacing these two hoses did not stop the P0171 and P0174 codes. Pretty damn sick of these codes!!!