Check Engine Light: P0171 & P0174

[loubutts]

have po171 and 174 also will ck vac leaks replaced plugs cleaned maf can use carb cleaner to ck for leaks is this an good idea and replacing intake manifold gasket that easy for an novist tks

 

[chrisfranco90]

its the intake gasket!

 

[chrisfranco90]

i was going thro the same thing its ur intake gaskets i got a ohv labor pretty though got it done in about 4 hrs but if u got a sohc itl be much easier ohv gasket kit cost bout 35bucks for sohc gasket kit cost bout 20 good luck

 

[drdoom]

Hose disconnected

The hose at the red arrow was causing my P0171/P0174. I had knocked it loose doing some other work.

 

[ivrb]

cold air filter

I had similar codes and a slight rattle on my 98 sohc. I did the oom12 kit myself and all the problems are cured.

will cold air free flow filters cause the 171 & 174 codes.

 

[ivrb]

Found my problem, the vac line that connects to the brake booster was on the wrong connection on the intake, the pcv was on the other switched them now the pcv hose connects straight in and seals, no more cel light

 

[expl0rerct]

In my case, my 2000 Explorer XLT with 4.0L SOHC had both P0171 and P0174 codes. As suggested by this post, I bought a can of electrical contact cleaner and cleaned my mass air flow sensor. I also checked and reseated the PCV valve to make sure the fit was snug. I cleared the codes by removing the battery cable negative terminal, and reconnecting it. So far the codes haven't come back for over 300 miles. For the record, I didn't have any rough idling or any indication of leaky upper/lower intake gaskets. I hope this helps. It saved me a lot of money.

 

[Keno Biebrich]

esos codigos son porque necesitas cambiar los empaques del aire de admision... estos empaques van en el plenum arriba y abajo del riel de injectores.....

tienes una entrada de aire y no puede controlarla la computadora....es todo!

 

[BonesDT]

esos codigos son porque necesitas cambiar los empaques del aire de admision... estos empaques van en el plenum arriba y abajo del riel de injectores.....

tienes una entrada de aire y no puede controlarla la computadora....es todo!

¿por qué sucede este post?

 

[rscamaro73]

Since this was dug up from the grave recently.....did anyone have any issues with upper RPM running with the same codes ? I have a 99 Xploder 5.0L

I have the same issues, also had a code that I thought was for a gas cap. Put a new cap, code never left. Just put another new cap and cleared codes but when I checked the stored codes it was for the P0171/0174. Have 3 stuck spark plugs on pass side to deal with, and a 1/2 stuck fuel filter.

But I digress.....to the upper RPM issue....above 3500rpm the truck loses power and doesn't want to go any faster, but when you let off the gas and the RPMs go down you can feel the speed and power pick up.

I was HOPING it'd be O2's.....but I bet the cat is clogged. I'm at 150K miles as well.

Thanks for any assistance. I'm going to see what my genius mechanic buddy what he thinks....but that'll be later this week.

 

[DannyNon]

Have a 1997 Mercury Mountaineer with codes. Any possibility of a missing "flap" entire plastic piece at the top of the fuel filler neck being the culprit allowing too much air in?

 

[99Explorer SOHC]

Bank 1&2 lean P0171 & P0174

So im pretty annoyed lol. 1999 explorer 4.0 SOHC throwing the CEL p0171 and p0174. I have replaced the upper and lower intake gaskets, PCV, IAC, MAF. CEL is still coming on. I noticed that the left hose off the "T" for the PCV is pinching shut while idling. I have 24 more days til my temporary tags are no longer valid. Please, any advice would be great. Thanks.

 

[blackshine007]

1998 Ford Explorer XLT 4.0 OHV


Got the P0171 and P0174 codes - wouldnt pass NYS Inspection.

1. Took it to Advance Auto - THEY looked it up and said O2 sensors for sure...
Found two Bosch direct fits - installed codes went away for 45 miles- then back
Still didnt pass inspection.

2. Took it to MIDAS - they tested with their machines and said it needed plenum gaskets - go to Ford and buy em and we'll install em- cheap. Went to Ford - got to Midas and they performed leak tests - said there wasnt an air leak - MUST be dirty fuel system & bad IAC. They did a fuel system cleaning and changed my IAC with one the manager just happened to have in his tool box. Too bad the IAC was for an SOHC. ( I found this out from the Ford PArts dept after the manager called him and the parts guy said the one he was putting in was the wrong part ) - yeah, I knew him .

3. Next stop was the Ford dealer - they looked at it, checked for vacuum leaks, found none, checked all intake no leaks they said, then they cleaned every waking inch of the MAF .Found it was the wrong IAC - cleaned my old one and put it back in. They did another computer diag and all was within normal limits. This solved the problem LONG enough for it to pass inspection ...LOL -- did I mention I used to be a lube tech there ? LOL

----- Of course within 50 miles the check engine light came on again.


So now I have invested all this time, a**ache and money into this and yet the check engine light is still on. I now have a slow coolant leak started at the mid - back section under my engine after having midas also do a flush and fill and replace the thermostat. ( which was malfunctioning and leaking out of the thermostat housing gasket before. )
And it isnt blowing smoke or anything that would lead me to suspect head gaskets ...

Thats about all the relevant information I have - any ideas ?


Thanks,

Mikki

This is the same exact issue that I have going on right now on a '98 explorer sport OHV. But there is no vacuum leaks. The MAF has been replaced. The one thing I have noticed that no one brought up was mentioning anything about fuel trim. Which is funny because when I turn the key on and don't start it the fuel trim is at 100% on both banks. When I take the negative and positive off and touch them together to reset fuel trim, the moment I plug in the scanner and look at fuel trim before even starting the truck the fuel trim is still at 100%. When I start it up, about 1 minute will go by until it goes into closed loop. There is no activity from the O2 sensors. The trim on the O2 sensors read 100%. When you unplug all 3 of them, it doesn't set a code. There's battery voltage to the heater on all 3. There's even ground. But on one of the wires there isn't continuity, which is common on the other connectors.We tried wiggling the harness with no success. The funny part about this story is that when all 3 O2 sensors are unplugged, no MIL is set, not even a pending code.



I'm fresh out of ideas. Anyone wanna take a stab at this?

 

[jonmcarr]

The hose at the red arrow was causing my P0171/P0174. I had knocked it loose doing some other work.

Does anyone know how to secure a replacement "hose" as referenced in DrDoom's picture? This is actually a Y connector that is part of the the IAC or Bypass airflow. Mine is torn to shreds. Local Ford dealer wants $213 for a replacement.

If no replacement choice other than dealer is out there, does anyone have a repair recommendation?

 

[HWBlock]

For PO171 / PO174 first item to check is ALL of the vacuum hoses including the PCV system for leaks. This OBD II combination is triggered by the computer calling for additional gas due to a vacuum leak, more gas less milage, engine coughs and sputters when cold. If all OK then suspect the Intake seals.

 

[BonesDT]

Does anyone know how to secure a replacement "hose" as referenced in DrDoom's picture? This is actually a Y connector that is part of the the IAC or Bypass airflow. Mine is torn to shreds. Local Ford dealer wants $213 for a replacement.

If no replacement choice other than dealer is out there, does anyone have a repair recommendation?

Not sure if this is obvious to you, but did you scour rockauto.com? If they don't have it, your options become slim.

As backups, I like to double check with Gates & Dorman's official website. Also check LMC Truck.

I would then direct my attention to junk yards. I couldn't believe how many Exs are in the PA jys these days.

If you have the OEM part number, search for it in Amazon. Some dealerships sell parts on there & you'll pretty much get the best stealership quote, but I'm not surprised by that insane price given these are very old models now.

If all else, get some generic auto hose and get to work with epoxy or electrical tape to get the Y. Whatever you do, please don't entertain that $213. Good luck.

 

[jonmcarr]

I have looked far & wide. I checked on used parts, but nothing was available locally (already pulled). I found out that Ford only sells the connector as part of the upper intake assembly, so at least you get something for the money.

A buddy suggested epoxy to seal the hose. It seems to have worked. The good news, truck is running great and think this is behind me.

Thanks for the response.

 

[Can EX]

I was getting the same codes on my 99 sport ohv. I changed the intake gaskets today now the truck won't start! Did anyone else have this happen. It cranks and I can smell fuel but the thing won't catch. It did once and shook like crazy at idle. Has this happened to anyone else? I'm pretty sure I've got everything back on and in the right spot's. I did however have the plug wires in the wrong spots on the coil's. I think I have them oriented right now though.

 

[seanshad]

these are the codes i was given by the shop!

any idea what to do to solve them??!?!!?

P0171 - system too lean B1
P0174 - system too lean B2

that and i am getting TERRIBLE GAS MILAGES.

this thing is killing me!

joel

Hi. Check your PCV Hoses routing specially at the trottle body the elbow hose. They tend to wear and cause a vacuum leak.

 

[gwedster]

try replacing the p.c.v. valve

these are the codes i was given by the shop!

any idea what to do to solve them??!?!!?

P0171 - system too lean B1
P0174 - system too lean B2

that and i am getting TERRIBLE GAS MILAGES.

this thing is killing me!

joel