I HAVE A 1997 FORD RANGER 4L.THE CHECK ENGINE LIGHT IS ON AND HAD THE CODES READ 171 174. ANY CLUES TO THIS PROBLEM?

 

This may help:

Codes P0172, P0174, P0171 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM
Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.

DTC P0172 bank 1 and DTC P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit.

HO2S DTCs Reference list:

HO2S-11 = DTCs P0171 and P0172
HO2S-21 = DTCs P0174 and P0175
Possible causes:

Fuel system

Excessive fuel pressure.
Leaking fuel injector(s).
High fuel pressure.
Low fuel pressure.
Contaminated fuel injector(s)
Ignition system

Spark plugs.
Spark plug wires.
Coils.
Induction system

Air leaks after the MAF sensor assembly.
Vacuum leaks.
Restricted air inlet.
PCV system.
Improperly seated engine oil dipstick.
Base engine

Oil overfill.
Cam timing.
Cylinder compression.
Exhaust leaks before or near the HO2S(s).
Check intake air system for leaks, obstructions and damage.
Check air cleaner element, air cleaner housing for blockage.
Verify fuel level.
Verify integrity of the PCV system.
Check for disconnected spark plug wires.
Check for vacuum leaks.
Verify customer did not run out of fuel.

Good Luck!

 

I just had the same codes, but on my Expedition. I found that my dipstick was sticking out a little bit. The O ring was not seated inside the tube. Reset the codes and has not come back on in 200 miles.


Bert

 

I CHECKED THE DIPSTICK AND FOUND NO PROBLEMS. THANKS FOR THE TIP.

 

I also cleaned the MAF sensor with electrical parts cleaner and dried it out. But the codes came back on. Dried it out by blowing compressed air on it.


Also cound be a leak in the PCV system. Check all the hoses good.


Bert

 

WHERE IS THE MASS AIR FLOW LOCATED .AND WHAT DOES THE MAF LOOK LIKE? I RECENTLY REPLACED THE PVC VALVE AND DO PLAN TO CHECK THE HOSES . THANKS AGAIN FOR THE HELPFULL INFORMATION.

 

The MAF sensor is right beyond the air filter. It is in the tube once you separate the air filter. It has two little wires in it.


Bert

 

My 97 4.0 Ranger had this problem (for a few years). I finally decided to change the plugs & wires. EGR was in two pieces (rust) so I decided to take it to a shop. I has around 100k miles. After this work was done, it still ran rough. The Mech, said the upper intake manifold gasket was leaking. He was able to verify it by spraying around the suspected area. The spray sucked into the gasket area and the engine ran fine for a few seconds.

I had the gasket replaced and the truck runs like new.

Kenny III