Truck throws P0171 and P0174 codes as soon as it runs a few minutes.
(Lean both banks) It does take a lot longer to throw the codes when using a K&N type filter instead of stock.
It runs great, idles fine and gets 17-19 MPG around town.
New air filter.
New fuel filter. (65 PSI)
Cleaned MAF and tried a different one.
No obvious vacuum leaks. (Propane test)
This truck does not have an EGR or DPFE.
Not sure if its related but the problem seemed to start after replacing the gas cap to fix the gas cap light.
Took it to the mechanic today. He could find no vacuum leaks but replaced the upper intake seals. Same problem.
He was extremely frustrated and said maybe the dealer can find something.
Any help or suggestions would be appreciated. It looks like I am falling into the same trap as almost everyone else with these codes.
The Ford dealer wants $150 flat rate to diagnose the problem. He said it is usually the lower intake gaskets. It would be sad to see this on a 36,000 mile truck.
What are the odds a smoke test would find anything?
Thank You
Our Sable threw the P0171 and P0174 codes. Wound up the hose off the PCV was crushed and split. This link should take you to a picture of it. Board Message
Check to see if your coolant reservoir is going down, even slightly. If it is it sounds like the lower intake gaskets are done. My dads ranger blew them out basically at 150k and it was pissing coolant all over the place.
carsrus: Did the leak take out the catalytic converter? Or was it an external leak... My old ride uses coolant a little, and I found a bit on top of the timing chain cover when it sat for a few weeks.
You could 'possibly' get a lean code if the engine is missing badly enough to leave unburned fuel/air in the exhaust. O2 is O2, and the sensor does not know the reason why.
Did you clean the injectors? Does it idle smoothly? Any burps or chugs accelerating or at cruise?
The symptom of the lean codes is drawn from the O2 sensor reporting a low voltage situation. The O2 generates voltage based upon the % of O2 in the gas passing by the sensor, after it has reached its operating temperature. My memory shaker is the phrase 'low is lean'. So, if the O2 sensors were dysfunctional, they would be reporting a lean condition. Have you tested the O2's? Are they old and poisoned? Did you ever feed them anti-freeze? Or RTV sealant or carb cleaner? Any of those can foul the O2 so they quit working. Then they report lean all the time... as they produce no voltage.
tom
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Last edited by tomw; 06-06-2009 at 11:04 AM.
Reason: more info.. and more
Possible causes
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 including Air leaks after the MAF, Vacuum leaks, PCV system, Improperly seated engine oil dipstick.
EGR system including Leaking gasket, Stuck EGR valve, Leaking diaphragm or EVR
Base engine including Oil overfill, Cam timing, Cylinder compression, Exhaust leaks befor or near the HO2S's
If you can check the value for SHRTFT-1 SHRTFT-2 should be between -25% to 35%
and LONGFT-1 LONGFT-2 between -35% to 35%. Readings beyond these values indicate a failure.
It is necessary to address all Continuous Memory Ignition and Misfire DTC's if received during Continuous Memory testing, before addressing any Fuel Trim DTC's, which is P0171 and P0174.
Check intake air system for leaks, obstructions and damage
Check air cleaner element, air cleaner housing for blockage
Verify integrity of the PCV system
Check fuel delivery system and filter ofr restriction
Check for vacuum leaks.
g_k50, what about the DPFE failure at ~60k miles? We have a 1997 3.8 Bird with 65k that just threw p0171 & p0174. It runs fine, no miss, no knock, no shaky idle, just turned on the CEL while pulling out of a shopping center. I had read that the DPFE can get corroded and mis-report the amount of EGR that is being flowed, thus misdirecting the ECM to enrich the fuel mixture.
PCV is OK, and power level seems fine. I just changed the air filter, and have hopes that will effect a cure... It was rather dirty, thus limiting air flow. How would that cause a lean report?
tom
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It's not how hard you work, it's how much you get done. Simplificate and add lightness
g_k50, what about the DPFE failure at ~60k miles? We have a 1997 3.8 Bird with 65k that just threw p0171 & p0174. It runs fine, no miss, no knock, no shaky idle, just turned on the CEL while pulling out of a shopping center. I had read that the DPFE can get corroded and mis-report the amount of EGR that is being flowed, thus misdirecting the ECM to enrich the fuel mixture.
PCV is OK, and power level seems fine. I just changed the air filter, and have hopes that will effect a cure... It was rather dirty, thus limiting air flow. How would that cause a lean report?
tom
I have a 2001 Emissions manual. I'm not sure how applicable it would be to a 1997. My 2001 Ranger 4.0L had a CEL that turned out to be the DFPE, I took it to the Dealer and he replaced it under warrenty because it was under 50,000 mi. But I did end up spending 500 on a tune up and brake work.
The CEL came on, and my wife took it to a parts place that would pull the codes. Maybe this will be my excuse to get an OBD-II reader.
I have the 97 shop manual on CD, but hadn't thought to look at the emissions stuff. Duh.
tom
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It's not how hard you work, it's how much you get done. Simplificate and add lightness
If you can check the value for SHRTFT-1 SHRTFT-2 should be between -25% to 35%
and LONGFT-1 LONGFT-2 between -35% to 35%. Readings beyond these values indicate a failure.
I'm getting a zero reading from my bank 1 rear O2 and a P0174 code. Could this be the culprit?
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2002 F-150 5.4L 4wd
Amsoil filter element w/ mod air box
Baer rotors EGR Carbon Kevlar pads
Flowmaster
Kenwood
Optima battery
Livewire PRP tuned w/wideband O2
Modified 4R70 Trans(shift kit)
4.88 gears and Trutrac carrier
B.F.Goodrich Rugged Trail
Stab the throttle ain't got no bottle http://i48.photobucket.com/albums/f2...0/100_0291.jpg
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