Codes PO171 & PO174 1999 Ford Explorer

[Alvin49tx]

Hi,
I have a 1999 Ford Explorer with the X vin # 4.0.
I keep getting codes
PO171 & PO174 about every three to four hundred miles.
I have check everything I can think of, Fuel Pressure is good hot and cold . all vacuum lines good , evaporated system all good PVC system is good.
I replaced the fuel filter when it first came on and thought that would fix it being it was almost stopped up .
I checked everything I know to check for this code . Has anybody run into this . All the onboard moniters will signal OK even with the codes set.
Maf sinals and pressues are good through out all my testing when road testing.
Any body got any ideals or have run into this before??
Alvin

[mab6680]

i had this problem about a week ago posted on this site same codes po171 -po174 banks 1 and 2 running lean my post should be a couple of lines down (check engine light) i have check all the same things you have they also said to clean the maf sensor i dont know if it worked or not i had to disconnect the battery for other reasons so the computer reset it self but i will let you know if it work you should clean it any way my mpg did go up so what could it hurt

[exploded99]

Originally Posted by mab6680

i had this problem about a week ago posted on this site same codes po171 -po174 banks 1 and 2 running lean my post should be a couple of lines down (check engine light) i have check all the same things you have they also said to clean the maf sensor i dont know if it worked or not i had to disconnect the battery for other reasons so the computer reset it self but i will let you know if it work you should clean it any way my mpg did go up so what could it hurt

Some weird things that might leak:

Brake power booster diaphragm ( they can be intermittent leaks)
Hose from power brake booster to manifold
Oil dipstick tube seal is shot, or not in tight
Oil filler cap loose / leaking
Evap vent solenoid hose to manifold cracked, bad
Vacuum lines for heater controls leaking - manifold to under dash
Leak at heater control valve
EGR vacuum supply line leaking
EGR tube from exhaust manifold to EGR valve leaking
EGR valve loose/leaking
Leak in exhaust system before O2 sensors
Cracked air intake tube from air filter to throttle body
Loose clamp on air intake tube
Leak around maf sensor itself
Any hose elbow on a vacuum line cracked
Valve cover loose
IAC valve loose or leaking
Throttle body gasket leaking
Leak at fuel injector O ring in manifold
Upper intake manifold to lower intake manifold gasket leaking

I am sure I forgot something. Some of that stuff is admittedly pretty unlikely. But a lot of it can be checked easily.

[mab6680]

this is right out of the ford service manual let me know if these things dont work i will post the next step


NOTE:
It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any Fuel Trim DTCs.

Fuel System DTC Reference List:

-- Bank 1 = DTCs P0171 (lean) and P0172 (rich)

-- Bank 2 = DTCs P0174 (lean) and P0175 (rich)

l Check intake air system for leaks, obstructions and damage.

l Check air cleaner element, air cleaner housing for blockage.

l Verify integrity of the PCV system.

l Check for vacuum leaks.

l Are any of the above concerns present?

Yes
REPAIR as necessary. COMPLETE KAM Reset.

No
GO to «DC25».

[drunkz]

i have a 1995 mercury grand marquis w codes po174 and po171 and dnt know wat to do sum 1 help

[sassee]

Don't know if you resolved this, but number one suspect is vacuum lines. be sure to check all lines and elbows.

[drunkz]

Originally Posted by sassee

Don't know if you resolved this, but number one suspect is vacuum lines. be sure to check all lines and elbows.

watb are the symtoms of a bad vacume line?

[sassee]

Depending on where the leak occurs, it could be either a high idle or a low, erratic idle. You could also have a leaking intake gasket, leaking PVC, etc. Take a can of carb cleaner and, with the engine running, spray the cleaner around all of the vacuum lines. Also spray around where all of your gaskets seat on the intake side. if you have a noticable change in engine idle, you've found your problem.

I chased a similar problem on my wifes' Sport Trac for a few months. the vacuum leak turned out to be on a hose that I had actually checked, but obviously didn't check well! the hose had a split on the bottom of it in the elbow. i guess the carb cleaner trick didn't hit the split and get sucked into the engine. replaced the $2 hose and it's been fine ever since. this was after $350 worth of perfectly good sensors were replaced though!


BE SURE TO WEAR SAFETY GLASSES AS THE CARB CLEANER WILL SCREW-UP YOUR EYES!!!

ernie

[drunkz]

i cleanes my maf sensor w maf cleaner and removed da throttle body and cleanes w cleaner and po171 and po401 are gone just have po174 ima check for a vacume leak

Originally Posted by sassee

Depending on where the leak occurs, it could be either a high idle or a low, erratic idle. You could also have a leaking intake gasket, leaking PVC, etc. Take a can of carb cleaner and, with the engine running, spray the cleaner around all of the vacuum lines. Also spray around where all of your gaskets seat on the intake side. if you have a noticable change in engine idle, you've found your problem.

I chased a similar problem on my wifes' Sport Trac for a few months. the vacuum leak turned out to be on a hose that I had actually checked, but obviously didn't check well! the hose had a split on the bottom of it in the elbow. i guess the carb cleaner trick didn't hit the split and get sucked into the engine. replaced the $2 hose and it's been fine ever since. this was after $350 worth of perfectly good sensors were replaced though!


BE SURE TO WEAR SAFETY GLASSES AS THE CARB CLEANER WILL SCREW-UP YOUR EYES!!!

ernie

[drunkz]

i found a hose dat had a whole in it and air was coming out ....i cleared da code and well c the results

Originally Posted by drunkz

i cleanes my maf sensor w maf cleaner and removed da throttle body and cleanes w cleaner and po171 and po401 are gone just have po174 ima check for a vacume leak