Help with Check engine light
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Joined: Dec 2005
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Help with Check engine light
Ok, Now what the hell went wrong. All I did was replace the stock exhaust with new pipe 2". and installed a Flowmaster 40 series SIDO muffler and two turndowns before the rearend now all of a sudden my check engine light came on with a P0171 and P0174 code. Both are for System Too Lean. Forgot to tell you that my truck is a 98' F-150 4.6 manual tranny. the rest of the truck is stock except the 265 tires. Has anyone else run into this. Any idea let me know.
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Joined: Jun 2002
Posts: 10,511
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From: Under the flightpath of old ORD 22R
Could be a few things. Could be as simple as a vac line was knocked off when doing the work, or could be more involved like the guy doing the work, loosened the XHST system by the O2 sensor.
I would start at the O2 snesors and check to see if the wiring was damaged, or if there is pressure on them, causing a leak.
Here is the full write up from the 2001 Service Manual, to give you some ideas of where to start looking for the problem. There are tons of posts on these codes, where you might find exact results from testing, to get an idea of most common causes.
DTC
P0174 - System to Lean (Bank 2) - see DTC P0171
DTC
P0171 - System to Lean (Bank 1)
Description
The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.
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:
- 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 HO2Ss.
Diagnostic Aides
A SHRTFT-1,2 PID value between -25% to +35% and a LONGFT-1,2 PID value between -35% to +35% is acceptable. Reading beyond these values indicate a failure.
I would start at the O2 snesors and check to see if the wiring was damaged, or if there is pressure on them, causing a leak.
Here is the full write up from the 2001 Service Manual, to give you some ideas of where to start looking for the problem. There are tons of posts on these codes, where you might find exact results from testing, to get an idea of most common causes.
DTC
P0174 - System to Lean (Bank 2) - see DTC P0171
DTC
P0171 - System to Lean (Bank 1)
Description
The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.
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:
- 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 HO2Ss.
Diagnostic Aides
A SHRTFT-1,2 PID value between -25% to +35% and a LONGFT-1,2 PID value between -35% to +35% is acceptable. Reading beyond these values indicate a failure.
