4.2L codes P0171 and P0175

04heritagev6 · #1 10-05-2009, 10:22 PM

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.

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daves03 · #2 10-05-2009, 10:41 PM

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

04heritagev6 · #3 10-05-2009, 11:28 PM

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

075SpdSTX · #4 10-06-2009, 05:23 AM

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.

ChrisT · #5 10-06-2009, 10:20 AM

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.

daves03 · #6 10-07-2009, 03:49 PM

Quote:

Originally Posted by ChrisT

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.

ChrisT · #7 10-07-2009, 04:01 PM

Quote:

Originally Posted by daves03

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.

04heritagev6 · #8 10-12-2009, 01:54 PM

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.