ok guys this is my first post and probably going to be a long one, so please bear with me. I purchased a well kept somewhat well maintained 2002 f150 with the 5.4l with 157k on the dash. general main was performed but beyond that not to much. the owner said it needed a new o2 sensor but somehow i knew it wasn't true. First codes thrown were 0153 and 0401. there is a exhaust leak seems to be coming from passenger side, it is getting fixed this upcoming weekend. I replaced all the hose dealing with the EGR and DPFE, that code has since been gone over 400 miles since deleted. code 0153 came back. also had a misfire on #5 replaced COP code has been gone. yesterday CEL came on figured 0153 popped back up and it did along with 0171 and 0173, from research 0171 seems to be a vac leak somewhere mostly commonly pcv line at back of motor the notorious elbow, 0173 was more of a mystery as i didn't find much on it, what i did find told me first areas to check were cleaning the MAF seņor and replacing the fuel filter. MAF was very dirty but is now clean and fuel filter was replaced and when old one was drained the fuel inside was rusty orange color, looked to be original fuel filter, reset CEL and drove rest of the day, no light came on but i got a hold of a Code reader that has live data, when i plugged it in i got 0171 but 0173 was gone, mind you no CEL was on at the time, MY STFT were +/-3% which seems to be normal operating range but my LTFT were 28%, crazy high. mind you these reading are at idle, with rpm up to 2000-2500 STFT remained same but LTFT dropped anywhere between 10-15%, i did this three times to get several readings and made sure it was in closed fuel loop. All of my O2 sensor were with in normal operating range. So i have replace #5 cop EGR/DPFE lines, fuel filter and exhaust manifold gasket to come. Tomorrow I am going to replace the PCV valve and lines. as to how the truck runs. The only issue i am having with the truck is horrible fuel mileage, so stalling sputtering stoppage or rough idle, everything is normal except fuel consumption barely getting 200 miles to a tank, granted i am running 35s with a 6" lift but it can't be zapping that many mpg's. so any other helpful hints, ideas, comments, concerns, bitches, gripes or moans? I am all ears

 

Your mileage check is going to be off unless the PCM was calibrated to adjust for the oversized tires. Check your speed with a GPS or smartphone app. If it is off, so is your mileage calculation.

Otherwise yes, a vacuum leak severe enough to set a code and wrong sized tires without low enough gears to push them can noticeably reduce mileage. These trucks don't get very good mileage anyway.

Also, O2 sensors are reasonably inexpensive and not too difficult to change. I know that is what the parts stores try to upsell you every time they code scan a vehicle, but oxygen sensors do sometimes go bad. ~$25 each on Rock Auto.

 

An exhaust leak before the O2 sensor can cause that lean code so don't go chasing vacuum leaks just yet. A leak in the PCV should cause both banks to trip lean, your 171 is bank #1 which is passenger side.

Not only can that lift and big tires kill gas mileage, but unless the speedo/odo have been corrected with a programmer you are traveling more miles than you think.

With 157k it would not hurt to replace both front O2's. Use only Motorcraft or Bosch.

If it has a K&N air filter or any other oiled filter, that is why the MAF was dirty. If this is the case, put a dry paper filter in and replace the MAF.

 

 

P0173 is not necessarily a lean code, it's a fuel trim malfunction bank 2. I would do the following:

1. Repair the exhaust leak.
2. Ditch the K&N and put a stock intake back on it. Best bet is a junkyard.
3. Replace both front O2's and the MAF with Motorcraft parts.
4. Replace the PCV valve and line from the valve to the intake. Use only a Motorcraft PCV.
5. Check for any more vacuum leaks, an unlit propane torch is good for this, if the gas hits a vacuum leak the fuel trims will jump.
6. Get a programmer and correct the speedo and odo. This doesn't affect just the speedo/odo, it also affects the PCM, it's getting incorrect speed data. Your in-law may be able to do this with his laptop and software. It may be trial and error, use a GPS to fine tune it. Shoot for 60 mph on the GPS and 62 on the speedo, that's how the factory sets it.
7. Clean the throttle body and consider getting a Motorvac or BG intake cleaning job. That K&N lets a lot of crap through along with the residual oil.

This is going to cost you, but it should be well worth it.

 

Ok so a little update to today. I go to pull the pcv valve out and the tubing and no surprise here is breaks right off in my hand at three different places. So safe to say there was a vac leak there as well. I have a bead on a guy who may want to swap air intakes with me. same year truck same motor and he was admiring my k&n and i said wanna trade. I am waiting for my cousin in law to have a open lift so I can fix the exhaust leak, but if it takes to much longer i may turn into a drive way mech and do it myself. Just not sure because I hear horror stories about the studs snapping and what not. either way, i reset my ecu numbers by dc the battery. Yes I know i may catch flax for doing it this way but it was the easiest fastest way for me to do it. STFT never went about +1 and would hover in the -3-0 range. I glanced at the LTFT but know that the numbers don't mean much as the ecu was reset, they were at zero, climbed a little bit and when i applied throttle shot right back to zero, going to assume which i hate doing that they rose due to the exhaust leak and the 02 sensors reading to much air there for boosting fuel... well you all get where i am going with this. anyways anyone in west palm beach have a tuner so i can program my truck for 35" tires

 

Check with your in-law. If he has a laptop and the Ford software he may be able to do it for you. Otherwise, the cheapest way is about $200 for a Superchips calibrator. You can't use someone else's tuner, it's locked to the VIN it's installed on, unless the tune is returned to stock.

 

I saw a Superchips 1715 for sale on ebay for $59 I think. That is what I have. I was looking on ebay because my cord has disappeared making me think the tire shops have taken it when i got my tires installed or balanced.

 

P0170/P0173 Fuel Control Malfunction
P0171/P0174 Fuel Control Lean
P0172/P0175 Fuel control Rich

Fuel Control and Fuel Trim are the same thing.