Engine Performance problem
2003 Ford F150 V8 Two Wheel Drive Automatic 108500 miles
2003 Ford F150 4.6l V8 W engine with reoccurring P0171 and P0174 codes, with engine idling rough at normal temp and dying when idling at normal temp. Engine seems to perform OK when given gas, and seems to run smooth at cold temp right when you crank it.
Air filter has been cleaned (it's a K& N CAI)
MAF sensor has been cleaned and replaced
No sounds of leaks anywhere when examined with stethoscope
PCV valve and hose has good suction when disconnected
Following procedures in Haynes book:
EGR vacuum regulator is receiving voltage, and ohms measured within range
DPFE has good reference voltage and signal voltage is within range at cold and warm temps
This is what I think:
According to the Haynes book, the EGR doesn't operate when the engine is cold. That's when the engine seems to run OK. It's only after the engine reaches normal temp that it begins to run rough. Also according to the book, too much EGR will cause the engine to run rough.
So, the next step is to replace the EGR valve? Should I go ahead and replace the oxygen sensors even though they're not throwing codes?
Saturday, May 16th, 2009 AT 3:12 PM