Hey guys well i really need some help with this 97 f150 with 140k miles. First it has given my friend nothing but problems since he bought it. I don't remember the codes it threw at first but it was the vacuum leak problem. He and I replaced all of the intake gaskets and sealed up all the vacuum hoses. It is completely airtight. Right after that the wires and plugs both went bad resulting in severe pinging. We replaced the plugs and wires and then the coil pack went bad as well. after doing all of this it was still throwing a P0171 and P0174 code for lean bank 1 and 2. We replaced both of the after cat o2 sensors and then both of those went away and then a P1131 code and a P1151 and about 6 dummy codes. We are unsure what to do at this point and any suggestions would be appreciated before more money is spent.

 

did you replace the isolator bolts when you replaced the intake gaskets?

 

When was the last time that the EGR ports have been cleaned? The new plugs are Motocraft right? What kinda shape is the battery in? How about the battery cables and terminals? Has the throttle body been cleaned out ever? Have you ever sprayed electronics cleaner on the mass air flow sensor to clean it? Have you checked the manifolds for any broken bolts that could possibly lead to an exhaust leak? Do you have any kind of tuner/programmer? When was the last time you have used any kind of injector cleaner? Have you tried wrapping the vacuum hoses with electrical tape at all the joints? Lastly, have you checked the PCV valve and PCV hose/elbow for leaks?

 

siunds to me like a trucks been neglected and now somone is wanting the cheap VS the correct way to repair it

 

Which engine does this truck have?

Replacing the after cat sensors was a total waste of money, all those do is report on catalyst efficiency.

 

It has the 4.6. And yes it was neglected by the previous owner i believe. My friend wanted to fix it up a little and get it running right but has been a nightmare of problems. And no he doesn't want the cheap way out. Isolator bolts were replaced as well. Before we replaced the after cat o2s it at least ran decent but had almost no power. After we replaced the o2s it seems like it wants to die at idle. It will jump from 400 to 600 rpm like crazy and is throwing the P1131 and P1151 which were never there before.

 

have you cleaned the IAT motor????

 

What is that? I don't know much about the fords yet i'm just doing my best to help out.

 

P0171, P0174, P1131, and P1151 all at the same time is a major vacuum leak or a ton of unmetered air coming in after the MAF sensor.

 

That is the strange thing. He only had the 171 and 174 code before the o2 sensors and before we replaced the gaskets. But as soon as we replaced the rear o2s the 1131 and 1151 showed up and the truck runs like crap.

 

Codes have absolutely nothing to do with the rear O2's, -thro that thought out.

The dummy codes you failed to post would be the missing clue, -post them all. Check the entire PCV line, something might not be plugged in specially in the back/ firewall. Your breather could be disconnected, it's something like that. Could be bad intake gasket install, it should be real obvious with those codes, -it's sucking so much air the computer can't even come close to compensate .

 

have the injectors overhauled or could possibly be the fuel regulator that has the vacuum line hooked up to it

 

Going back to the original post, what do you mean by "sealed up all the vacuum hoses. It is completely airtight." Did you replace broken hoses, or just remove the hoses and plug the fittings? I agree with the earlier posts, you have a massive vacuum leak somewhere. The 4.6l are notorious for PCV leaks where the hose connects to the rear of the intake manifold, right where it's near impossible to see or repair. With the engine running, you might be able to stick your hand back there and move some of the hoses around and listen for the sound of sucking air to change. I'd also check the brake booster and its hoses.

 

There was also a TSB issued that suggests it might be a bad/contaminated MAF sensor:
Article No.
98-23-10

11/23/98
MASS AIR FLOW (MAF) - SENSOR
CONTAMINATION - SERVICE TIP

FORD:
1990-97 THUNDERBIRD
1990-99 MUSTANG, TAURUS SHO
1991-99 CROWN VICTORIA, ESCORT, TAURUS
1992-94 TEMPO
1993-97 PROBE
1995-99 CONTOUR

LINCOLN-MERCURY:
1990-97 COUGAR
1991-99 CONTINENTAL, GRAND MARQUIS, SABLE, TOWN CAR, TRACER
1992-94 TOPAZ
1993-98 MARK VIII
1995-99 MYSTIQUE

LIGHT TRUCK:
1990 BRONCO II
1990-97 AEROSTAR
1990-99 RANGER
1991-99 EXPLORER
1994-96 BRONCO
1994-97 F SUPER DUTY, F-250 HD
1994-99 ECONOLINE, F-150, F-250 LD, F-350
1995-99 WINDSTAR
1997-99 EXPEDITION, MOUNTAINEER
1998-99 NAVIGATOR
1999 F-250 HD, SUPER DUTY F SERIES

ISSUE
This TSB article is a diagnostic procedure to address vehicles that exhibit lean driveability symptoms and may or may not have any Diagnostic Trouble Codes (DTCs) stored in memory.

ACTION
Follow the diagnostic procedures described in the following Service Tip. The revised diagnostic procedure is a more accurate means of diagnosing the symptoms.

SERVICE TIP

MASS AIR FLOW (MAF) DISCUSSION

MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.
NOTE THE FOLLOWING PROCEDURE MAY ALSO BE USED TO DIAGNOSE VEHICLES THAT DO NOT HAVE FUEL SYSTEM/HO2S SENSOR DTCS.

Symptoms
^ Lack of Power

^ Spark Knock/Detonation

^ Buck/Jerk

^ Hesitation/Surge on Acceleration

^ Malfunction Indicator Lamp (MIL) Illuminated -

DTCs P0171, P0172, P0174, P0175 may be stored in memory

OBDII DTCs
^ P0171, P0174 (Fuel system lean, Bank 1 or 2)

^ P0172, P0175, (Fuel system rich, Bank 1 or 2)

^ P1130, P1131, P1132, (HO2S11 lack of switching, Bank 1)

^ P1150, P1151, P1152, (HO2S21 lack of switching, Bank 2)

OBDI DTCs
^ 181, 189 (Fuel system lean, Bank 1 or 2)

^ 179, 188 (Fuel system rich, Bank 1 or 2)

^ 171, 172, 173 (HO2S11 lack of switching, Bank 1)

^ 175, 176, 177 (HO2S21 lack of switching, Bank 2)

^ 184, 185 (MAF higher/lower than expected)

^ 186, 187 (Injector pulse width higher/lower than expected)

NOTE O NOT DISCONNECT THE BATTERY. IT WILL ERASE KEEP ALIVE MEMORY AND RESET LONG TERM FUEL TRIM AND BARO TO THEIR STARTING/BASE VALUES. THE BARO PARAMETER IDENTIFICATION DISPLAY (PID) IS USED FOR THIS DIAGNOSTIC PROCEDURE. ALL OBDII APPLICATIONS HAVE THIS PID AVAILABLE. THERE ARE SOME OBDI VEHICLES THAT DO NOT HAVE THE BARO PID, FOR THESE VEHICLES OMIT THE BARO CHECK AND REFER ONLY TO STEPS 2, 3, AND 4 IN THE DIAGNOSTIC PROCEDURE.


1. Look at the BARO PID. Refer to the Barometric Pressure Reference Chart in this article. At sea level, BARO should read about 159 Hz (29.91 in. Hg). As a reference, Denver, Colorado at 1524 meters (5000 ft.) altitude should be about 144 Hz (24.88 in.Hg). Normal learned BARO variability is up to +/- 6 Hz (+/- 2 in. Hg.). If BARO indicates a higher altitude than you are not at (7 or more Hz lower than expected), you may have MAF contamination. If available, Service Bay Diagnostic System (SBDS) has a Manifold Absolute Pressure (MAP) sensor that can be used as a barometric pressure reference. Use "MAP/BARO" test under "Powertrain," "Testers and Meters." Ignore the hookup screen. Connect GP2 to the reference MAP on the following screen.

NOTE REMEMBER THAT MOST WEATHER SERVICES REPORT A LOCAL BAROMETRIC PRESSURE THAT HAS BEEN CORRECTED TO SEA LEVEL. THE BARO PID, ON THE OTHER HAND, REPORTS THE ACTUAL BAROMETRIC PRESSURE FOR THE ALTITUDE THE VEHICLE IS BEING OPERATED IN. LOCAL WEATHER CONDITIONS (HIGH AND LOW PRESSURE AREAS) WILL CHANGE THE LOCAL BAROMETRIC PRESSURE BY SEVERAL INCHES OF MERCURY (+/- 3 Hz, +/- 1 in. Hg.).

NOTE BARO IS UPDATED ONLY WHEN THE VEHICLE IS AT HIGH THROTTLE OPENINGS. THEREFORE, A VEHICLE WHICH IS DRIVEN DOWN FROM A HIGHER ALTITUDE MAY NOT HAVE HAD AN OPPORTUNITY TO UPDATE THE BARO VALUE IN KAM. IF YOU ARE NOT CONFIDENT THAT BARO HAS BEEN UPDATED, PERFORM THREE OR FOUR HEAVY, SUSTAINED ACCELERATIONS AT GREATER THAN HALF-THROTTLE TO ALLOW BARO TO UPDATE.

2. On a fully warmed up engine, look at Long Term Fuel Trim at idle, in Neutral, A/C off, (LONGFT1 and/or LONGFT2 PIDs). If it is more negative than -12%, the fuel system has learned lean corrections which may be due to the MAF sensor over-estimating air flow at idle. Note that both Banks 1 and 2 will exhibit negative corrections for 2-bank system. If only one bank of a 2-bank system has negative corrections, the MAF sensor is probably not contaminated.

3. On a fully warmed up engine, look at MAF voltage at idle, in Neutral, A/C off (MAF V PID). If it's 30% greater than the nominal MAF V voltage listed in the Powertrain Control/Emissions Diagnosis (PC/ED) Diagnostic Value Reference Charts for your vehicle, or greater than 1.1 volts as a rough guide, the MAF sensor is over-estimating air flow at idle.

4. If at least tow of the previous three steps are true, proceed to disconnect the MAF sensor connector. This puts the vehicle into Failure Mode and Effects Management (FMEM). In FMEM mode, air flow is inferred by using rpm and throttle position instead of reading the MAF sensor. (In addition, the BARO value is reset to a base/unlearned value.) If the lean driveability symptoms go away, the MAF sensor is probably contaminated and should be replaced. If the lean driveability symptoms do not go away, go to the PC/ED Service Manual for the appropriate diagnostics.

NOTE DUE TO INCREASINGLY STRINGENT EMISSION/OBDII REQUIREMENTS, IT IS POSSIBLE FOR SOME VEHICLES WITH MAF SENSOR CONTAMINATION TO SET FUEL SYSTEM DTCs AND ILLUMINATE THE MIL WITH NO DRIVEABILITY CONCERNS. DISCONNECTING THE MAF ON THESE VEHICLES WILL, THEREFORE, PRODUCE NO IMPROVEMENTS IN DRIVEABILITY. IN THESE CASES, IF THE BARO, LONGFT1, LONGFT2, AND MAF V PIDs INDICATE THAT THE MAF IS CONTAMINATED, PROCEED TO REPLACE THE MAF SENSOR.

After replacing the MAF sensor, disconnect the vehicle battery (5 minutes, minimum to reset KAM, or on newer vehicles, use the "KAM Reset" feature on the New Generation Star (NGS) Tester and verify that the lean driveability symptoms are gone.
OTHER APPLICABLE ARTICLES:: NONE
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 206000, 610000, 610500, 610600, 610700, 611000, 611500, 612000, 612500, 614000, 614500, 614600, 698298