aamoedo

iTrader: (2)

I did some searching but wasn't finding too much helpful information. Here are the details on the car.

Engine

• Apexi world sport exhaust
• Titec O2 housing
• HKS 3" Downpipe
• Rally Cat Testpipe
• AEM Intake
• Cosworth M2 cams with Supertech springs and retainers
• ARP head studs
• FIC 1450cc injectors
• Walbro 255lph fuel pump
• Denso Iridium IKH24 (one step colder)
• Tuned for 91 and E85 by Sean at FFTEC

So this weekend I drove up from San Francisco to Russian River (40 miles). Car did fine all day, even had a spirited drive up near Santa Rosa with no problem. I drive the car all the way back to the city (40 miles or so) and it drives completely fine. I drop my girlfriend off in front of my apartment with groceries while I go park the car, and then the car throws the code. P0171 lean.

Not sure what to make of this. Here are a couple thoughts, all of which may or may not have any bearing. The car has mostly been driven on E85 before I bought it. I just finished my first tank back on 91. I talked to the previous owner and he has never had any codes thrown with the car. So this is kind of a fluke. I do get a low idle issue very rarely, but the previous owner said this happened to him as well, and that Sean said it was normal.

Any ideas? Should I be scared to drive the car right now? Suggestions? Being in the city, I don't really have a shop or place to start tearing stuff apart. I cleared the code for now and was going to baby the car this weekend and see if it comes back on. Should I avoid doing this? The car drives like a champ.

aamoedo

iTrader: (2)

Nobody has any ideas?

Fast_Freddie

iTrader: (50)

Mine just did the same thing when I went from E85 back to 93oct... Thought it was the O2 Sensor, so replaced it with no change... I reset the computer and let it relearn fuel trims and stuff and all is good...

evo8426

iTrader: (27)

Does the light come back frequently? If it does it every once in a while I would just ignore it. I usually throw a code when running pump for a long period of time and then switch to e85 and vise versa.

aamoedo

iTrader: (2)

This is the first time it has done it. I don't think it has been run on 91 for quite some time. My gut told me this might be the cause, but I just wanted to double check. I haven't driven it since I cleared the code the other day. It's a weekend car for me. I'll just keep an eye on it, and double check any lines that might have come loose just in case.

mrm95

iTrader: (1)

Mine has been doing this also. I found a vacumm leak and deleted the code and 100 miles later the CEL came back.

Fox5.56

Mine started doing the same, I have a few vaccum leaks I think though. EGR valve keeps falling off for one.

shavkatjon2000

iTrader: (7)

DTC P0171: System too Lean

System too Lean Circuit
- Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.

CIRCUIT OPERATION
- Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.

TECHNICAL DESCRIPTION
- If a malfunction occurs in the fuel system, the fuel trim value becomes too large.
- The ECM checks whether the fuel trim value is within a specified range.

DESCRIPTIONS OF MONITOR METHODS
- Air/fuel learning value (long term fuel trim) and air/fuel feedback integral value (short term fuel trim) are too lean.

MONITOR EXECUTION
- Continuous

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Misfire monitor

Sensor (The sensor below is determined to be normal)
- Volume airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor

DTC SET CONDITIONS



Logic Flow Chart

Check Conditions
- Engine coolant temperature is lower than approximately 100 degrees C (212 degrees F) when the engine is started.
- Intake air temperature is lower than 60 degrees C (140 degrees F) when the engine is started.
- Under the closed loop air/fuel ratio control.
- Engine coolant temperature is higher than 76 degrees C (169 degrees F).
- Volume airflow sensor output frequency is 56 Hz or more.

Judgment Criteria
- Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds

or

- Short-term fuel trim has continued to be higher than +10.0 percent for 5 seconds.

Check Conditions
- Engine coolant temperature is lower than approximately 100 degrees C (212 degrees F) when the engine is started.
- Intake air temperature is lower than 60 degrees C (140 degrees F) when the engine is started.
- Under the closed loop air/fuel ratio control.
- Engine coolant temperature is higher than 76 degrees C (169 degrees F).
- Volume airflow sensor output frequency is 56 Hz or less.

Judgment Criteria
- Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds.

or

- Short-term fuel trim has continued to be higher than +15 percent for 5 seconds.

Check Conditions
- Engine coolant temperature is higher than approximately 100 degrees C (212 degrees F) when the engine is started.
- Intake air temperature is higher than 60 degrees C (140 degrees F) when the engine is started.
- Under the closed loop air/fuel ratio control.
- Engine coolant temperature is higher than 76 degrees C (169 degrees F).
- Volume airflow sensor output frequency is 56 Hz or more.

Judgment Criteria
- Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds.

or

- Short-term fuel trim has continued to be higher than +20.0 percent for 5 seconds.

Check Conditions
- Engine coolant temperature is higher than approximately 100 degrees C (212 degrees F) when the engine is started.
- Intake air temperature is higher than 60 degrees C (140 degrees F) when the engine is started.
- Under the closed loop air/fuel ratio control.
- Engine coolant temperature is higher than 76 degrees C (169 degrees F).
- Volume airflow sensor output frequency is 56 Hz or less.

Judgment Criteria
- Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds.

or

- Short-term fuel trim has continued to be higher than +25.0 percent for 5 seconds.

Check Conditions
- Engine coolant temperature is higher than 76 degrees C (169 degrees F).
- Under the closed loop air/fuel ratio control.

Judgment Criteria
- Long-term fuel trim has continued to be +12.5 percent for 2 seconds.

or

- Short-term fuel trim has continued to be +25.0 percent for 2 seconds.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 20. See: Computers and Control Systems > Monitors, Trips, Drive Cycles and Readiness Codes > OBD-II Drive Cycle Pattern Lists

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are
- Volume airflow sensor failed.
- Injector failed.
- Incorrect fuel pressure.
- Air drawn in from gaps in gasket, seals, etc.
- Heated oxygen sensor failed.
- Engine coolant temperature sensor failed.
- Intake air temperature sensor failed.
- Barometric pressure sensor failed.
- Use of incorrect or contaminated fuel.
- ECM failed.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B

STEP 1. Check for exhaust leaks.

Q: Are there any abnormalities?

YES: Go to Step 2.

NO: Repair it. Then go to Step 14.

STEP 2. Check for intake system vacuum leaks.

Q: Are there any abnormalities?

YES: Go to Step 3.

NO: Repair it. Then go to Step 14.

STEP 3. Using scan tool MB991958, check data list item 12: Volume Airflow Sensor.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

if you need a copy of it i have a alldata access so i can email you or message you its like half of it