Mechanics

F150 4.2 IDLES ROUGH

1997 Ford F-150

Engine Performance problem
1997 Ford F150 6 cyl Two Wheel Drive Automatic 70700 miles

My truck keeps giving me the P0174, P0302, and P0303 codes. On rare occasions I get a P0172. I have replaced the 2 Front O2 sensor, TPS and Catalytic Converters. I have also cleaned the MAP, MAF and the IAC. I get the 303 and 302 codes at idle or low RPM. When I am driving at abour 55-60 is when the 174 code shows up. I have checked for vaccum leaks by listening for them and spraying starting fluid on the vaccum lines but I cannot find a leak. I hope that you would have some advice on what I should check next. I have a diagnostic code reader but it does not give me much info. I can get the fuel trim and that is about the most advanced info I get from it.
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Jay.strawder
March 10, 2009.



P0174

A lean fuel condition can be caused by: * Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires

Rasmataz
Mar 10, 2009.
I have cleaned the MAP and MAF sensor, replaced the air filter. I have put the Injector cleaner in the last 2 tanks of fuel. I have lost the #2 cylinder misfire, but I have the #3 misfire and P0174. I am checking the EGR valve now. I have taken it off and cleaning it and checking for proper operations. I will let you know if I figure anything out.

Tiny
Jay.strawder
Mar 13, 2009.
What is normal fuel trim for 4.2? I think mine is out of tolerance. What control is? I have now checked the egr and it works fine, replaced the egr solenoid and the egr pressure switch as well.

Tiny
Jay.strawder
Mar 15, 2009.
Normally its plus or minus 20% what controls it are these related sensors, coolant, throttle, intake and oxygen sensors-

Rasmataz
Mar 15, 2009.