I have a 2004 f-150 heritage 4.2L v6. The service engine soon light came on and it started running bad. It hesitates and skips when accelerating and has rough idle. I had it scanned and it showed codes P0171 (too lean bank 1) and P0175 (too rich bank 2). I cleaned the MAF sensor, changed the fuel filter, and changed the O2 sensor on the driver's side. Still showing the same codes and still running rough. Help please, I am in the military and don't have alot of free time to take it to a shop.

 

Check for vacume leaks. All hoses and even the ones that are near the rear of the engine.

 

how can i check for vacuum leaks. what equipment do i need?

 

Get a can of WD-40 and spray where you may have a possible leak. If the motor revs you've found the area of the leak. Then isolate the exact location.

 

Specifically, I'd check\replace your PCV elbow. It's a common issue with our engine and it's only about a $15 part I believe. I had the same issue on my truck around 90K miles. I replaced the PCV elbow, upper and lower intake gaskets and the isolator bolts for the plenum, which I believe there was a TSB for. Good luck.

 

Chris, would i be in the clear for the intake gaskits? Mine is an 03 and uses no coolent.

 

Not necessarily. I think you are referring to the lower intake gasket issue that caused the hydro-lock on the 97-98's due to coolant leaking. My issue was my upper intake manifold or intake plenum. What happens is, the rubber gaskets get worn out causing a vacuum leak, a very common issue on our engines. I also got a new set of isolator bolts (from Ford parts desk) to fasten the intake plenum. Since we were taking it all apart, I went ahead and did the lowers as well.

 

Well, I ended up taking it to a shop.....It turns out that the catalytic converters were bad and were triggering the codes. I had them replaced and no more problems. Thanks for all the suggestions.