P1151, P0171, P0174, can't find vaccum leak 4.6 trition

Hi, this is my first post although i have been browsing the forums for a while. I have seen that a lot of folks have had similar issues as myself. I have owned my 2003 expedition xlt (4.6) for about six months. It had an intermittent misfire at high speeds on cylinder 7 until I replaced the spark plugs and a faulty coil a couple weeks back. I didn't get to this until now because I was having financial problems and don't drive on the highway much so the misfire was a rare occurrence. Now that I have fixed the misfire, I am getting codes P0171, P0174, and P1151. This leads me to believe that I am facing a vaccum leak because the truck idles roughly but drives fine. I tried the carb cleaner method today to try to find the leak, but I didnt notice any change in idle rpm. After visually inspecting the vaccum hoses, I couldnt find any evident leaks. I checked the infamous PCV valve, however I have the cooled PCV valve with coolant hoses attached to the elbow. I didnt notice any damage in the elbow. How should I proceed to diagnose the issue. It is not clear to me at this point whether the problem is certainly a vaccum leak or could be something else such as a bad sensor or plugged cat (because I ran the truck with a misfire for months). Anyone else have similar issues, if so, how did you solve them? Thanks for any help you folks can give.

If you can get your hands on a small scan tool it would be nice. The local wal-mart in my neck of the woods stock a little 4 button Autel for $40 which has live data in addition to being able to read codes. I think it would be a lot better to check for vacuum leaks by looking at the fuel trims while someone sprays propane or something in the engine bay since sometimes it's hard to tell by using your ear and listening to changes in RPM.

There's a lot of things that you can rule out by looking at the live data feed. Seeing how both banks are lean at the same time it could indicate a fuel delivery problem or maybe something as simple as a dirty MAF. A dirty MAF is something that I consider to be a 'freeby' fix - just get some MAF cleaner and have a go at it.

Read the attached link.


I first would resolve the P0171 and P0174 issues before doing the P1151 issue
How many miles on the expy??
You stated you changed #7 plug and coil DID you replace any other plugs and coils??
Check your fuel pressure
Replace fuel filter
check the exhaust riser to the EGR valve (drivers side) and the rubber hoses that go to the DPFE sensor


http://troubleshootmyvehicle.com/ford/4.6L-5.4L/troubleshooting-p0171-and-p0174-page-1

P0171 - System to Lean (Bank 1)
P0174 - System to Lean (Bank 2)

The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information



Air Measurement System

• MAF sensor (contaminated, damaged, malfunctioning, etc.)

Fuel System

• Fuel pressure regulator (leaking, malfunctioning, etc.).
• Fuel filter plugged, dirty.
• Fuel pump (weak, check valve leaking, etc.).
• Leaking/contaminated fuel injectors.
• Low fuel pressure or running out of fuel.
• EVAP canister purge valve leaking (when canister is "clean").
• Fuel supply line restricted.
• Fuel rail pressure sensor (incorrect reading).

Air Induction System

• Air leaks after the MAF.
• Vacuum Leaks.
• PCV system (leak, valve stuck open, etc.)
• Improperly seated engine oil dipstick.

Exhaust System

• Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets, etc.)..

EGR System

• EGR valve tube/gasket leak
• EVR solenoid vacuum leak

Secondary Air Injection

• Damaged/malfunctioning secondary air injection system (mechanically stuck valve).

View Freeze Frame Data to determine operating conditions when DTC was set. Observe LONGFT1 and 2 PID(s). Refer to Section 2 ,

View Freeze Frame Data to determine operating conditions when DTC was set. Observe LONGFT1 and 2 PID(s). Refer to Section 2 , Adaptive Fuel DTCs Diagnostic Techniques for more information


P1151 - Lack of HO2S-21 Switch, Sensor Indicates Lean

A HEGO sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when fuel control system no longer detects switching for a calibrated amount of time.

See Possible Causes for DTC P1130

• Electrical:
  • Short to VPWR in harness or HO2S
  • Water in harness connector
  • Open/Shorted HO2S circuit
  • Corrosion or poor mating terminals and wiring
  • Damaged HO2S
  • Damaged PCM
• Fuel System:
  • Excessive fuel pressure
  • Leaking/contaminated fuel injectors
  • Leaking fuel pressure regulator
  • Low fuel pressure or running out of fuel
  • Vapor recovery system
• Induction System:
  • Air leaks after the MAF
  • Vacuum Leaks
  • PCV system
  • Improperly seated engine oil dipstick
• EGR System:
  • Leaking gasket
  • Stuck EGR valve
  • Leaking diaphragm or EVR
• Base Engine:
  • Oil overfill
  • Cam timing
  • Cylinder compression
  • Exhaust leaks before or near the HO2S(s)

Buy yourself a smoke machine off ebay. You'll save yourself time and money. It can be a cracked intake manifold, bad intake gaskets, bad vacuum hose, or any combination there of ...
Other than that take it to a shop and let them do it. 'Cause that's what they're gonna use.

-Mike



https://www.ebay.com/itm/Stinger-EV...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Im currently at 198xxx miles. I changed all of the plugs and didn't change any coils except number 7. I cleaned the MAF yesterday and cleared the light. It came back on this morning.

I just fixed my lean codes. I had the same as you, except I didn't get the P1151. I found my intake gasket was leaking by poking a hole in the top of a water bottle and then spraying water around the base of the intake while listening. Like you, I could never detect a difference with Carb or Brake cleaner spraying. The passenger side was fine on mine, but the driver side would nearly die when sprayed near the back, and you could hear the water being sucked in at the front.

So I replaced my gaskets, which is a pain, but not difficult. While I was doing that job though I found think I found what was actually setting the codes was a cracked rubber coupler for the vacuum harness that connects it to the vacuum reservoir right in front of the PCM on the passenger side firewall. It was a pain to find, but it was cracked bad. So also check all those little unions for the vacuum lines as well.

Im gonna get a scan tool this weekend and check fuel trims. Today I checked my oil and it was chronically low. Apparently my oil pressure sending unit has gone bad. Im going to go ahead and replace this as soon as I can, but could these two problems be related? Is there a chance that the bad oil sending unit or low oil pressure could be causing the codes? Thanks for the tips

Okay, I think I have figured out the problem. After watching this video, , I realized that my truck is making the same sound. I think perhaps I have an exhaust manifold leak and that's what is causing the clicking sound and lean codes

Just make sure you verify the PCV elbow is still good.
Mine was bad and caused P0171 P0174 codes.
http://www.expeditionforum.com/threads/obdii-reader.34543/