1997 Ford F-150 4.2 Idles Rough

Tiny
JAY.STRAWDER
  • MEMBER
  • 1997 FORD F-150
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 70,700 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.
Tuesday, March 10th, 2009 AT 6:07 PM

4 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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
Was this
answer
helpful?
Yes
No
Tuesday, March 10th, 2009 AT 6:10 PM
Tiny
JAY.STRAWDER
  • MEMBER
  • 3 POSTS
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.
Was this
answer
helpful?
Yes
No
+1
Friday, March 13th, 2009 AT 2:58 PM
Tiny
JAY.STRAWDER
  • MEMBER
  • 3 POSTS
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.
Was this
answer
helpful?
Yes
No
+1
Sunday, March 15th, 2009 AT 1:12 AM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Normally its plus or minus 20% what controls it are these related sensors, coolant, throttle, intake and oxygen sensors-
Was this
answer
helpful?
Yes
No
+1
Sunday, March 15th, 2009 AT 4:21 PM

Please login or register to post a reply.

Related Engine Idle Rough Content

Rough Engine Idle
GUIDE
Rough Engine Idle
A rough engine idle condition is a common issue that many drivers face often indicating underlying problems within the engine, fuel or ignition system. We have created this...
VIEW MORE