I went by Autozone at lunch to get my computer scanned and they picked up the above codes, but couldn't help much more than that.

Any ideas on what needs replacing?

My Check Engine light is on, and I'm having really bad idle problems when the engine is cold. Once it warms up, no real indication that anything is amiss.

Mine is an '99 XLT Explorer, with 48,000 miles, and the 4.0L SOHV engine.

Thanks in advance,
Harold Jones

 

DOH!!! I just noticed a very similar post below about the same codes and OOM12 Owner Notification Program. Sorry...next time I'll search the archives first.

I had taken it to a local shop before I found this site. The local shop had tried to sell me new O2 sensors, platinum plugs, wires, fuel filter, PVC assembly, all for the low low price of $541. Not!

Thanks again,
Harold
'99 XLT Explorer 4.0LSOHV
'88 TT Mustang Coupe

 

Thanks to those who posted of the above ONP. That is exactly what was wrong with my '99. Dealer fixed it and all is well. @#$%$@ the local shop who wanted the $541 for O2 sensors, new plat. plugs, wires, fuel filter, and PVC valve...glad I didn't trust my gut instinct.

Thanks again,
Harold Jones
'99 Explorer XLT 4.0L SOHV
'88 Mustang LX TT Coupe

 

Hey Harold,
I have the same problem... the same car, '99 Exp. 4.0 SOHC...

Problem: I can't find the PCV valve, where is located on the engine?
thanks!!
Bill

 

The PCV is behind the center of the intake manifold. It has 2 hoses going to it from the sides and it fits into a hose that goes down from it to the engine. You can get at it easiest from the passenger's side of the engine.

There are couple of posts on this site regarding this.

Mike

 

I searched for this info and couldn't find it...
also, the local auto shop sold me the same PVC valve that goes on my '95 Explorer w/4.0 (non SOHC). It doesn't have a T. So I guess I need to take it back and get the right one...

thanks for the info.
Profanity Removed

 

I just took my 99 4.0 SOHC to Auto-Zone and got the same code,PO171, and PO174. I had to chang one of the o2 sensors 2 months ago but now I'm hoping I can get by with just a PCV valve. They told me that it is probably water in the gas lines , or a vacum leak. Has anyone experienced that and if so, what did you do? This is my first time here so any help would be great.

Thanks, Tom Frazier:-(

 

Your lower intake manifold o-rings are probably leaking. Ford extended the warranty on them to 6 years, 72K miles through ONP 00M12. Those are the same two codes mine had when mine leaked.

 

Thanks for the info. If the light comes back on I will call the hotline to get this taken care of. I'm also getting the rattle when it starts. Sounds like Ford will be doing some free work.

 

Just had the same issue - after spending $$$ dollars on dealer diagnostics (we can't replicate your code) I took it to the AAA diagnostic center. I had a faulty downstream O2 sensor. AAA recommended an indendednt shop and I had it replaced for $90 parts included.

There is a TSB on these codes which discusses these other possibe causes for these codes: Upper Intake Manifold Leaks -(O rings and Gasket), Vacuum Leaks, Oil Dip Stick not seated corretly, Fuel Filter clogged, fuel lines kinked, MAF sensor dirty, Crack at Fuel Filler Tube, Fuel Cap not seated correctly, Clogged Fuel injectors and some others.

I would suggest using a AAA diagnostic center if you are near one. Diagnostics are done for a flat fee of $80 in PA. Four hours of testing and they replicated my problem. Now if I had only done that first!!!!

 

I also had a faulty O2 sensor. I replaced it 2-3 months ago and the problem was taken care of, or was it?
The stories I read at the other forum page seem to hit home with my Explorer. The mileage is about the same as the ones I read about and the symtoms. I do not have a AAA center near me. I'm not sure what code came up when I was told to replace the O2 sensor.
I do know this though, I wouldn't want to change the PCV valve very often. What a pain!!!! I haven't checked, but does anyone know where the fuel filter is located?
I'm assuming it's on the frame undeneath.



Thanks

 

Thanks for the info about the intake o-rings. I took mine to the Ford Garage and they did a test and found a leak around the lower intake gasket. It was fixed under the Ford recall 00M12. This forum saved me some money. Thanks again.

 

Here is the fix!!!......unbuckle the air cleaner, spray (for (2) 10 second blasts) the two wires in the throat of the MAF sensor with non-residue, solvent based electronic cleaner.......rebuckle the air cleaner and reset the P0171 and P0174 codes with a OBD II analyser.

That will fix it!!

Mike Mulhern
Scottsdale, AZ

 

Only if your MAF sensor is dirty. If the codes are the result of leaking lower intake manifold o-rings, no amount of cleaning to the MAF is going to fix that.