shawn101

hi every one
just joined in have a question if some one can help me solving it. i have 04 civic coupe i don't know if its dx/ex/lx or ? sudenly engine light came ON this morning and i scanned it with innova scan tool it gave me code P0171 which is (FUEL METERING TOO LEAN) and i don't know what could be the problem. thanks in advance

dliberty

Well, there are a few things that can cause that code. Basically your ECU threw the code because the information it is receiving from your cars sensors mathematically does not make sense. I had a similar code (p0128) which is thrown when the car does not heat up over a certain period of time after a cold start. The fix for this was a PCM update and a coolant change. Do you know if your civic has the most recent PCM update? Also, Fuel metering to lean indicates that your engines fuel/air ratio is not to spec. It does not necessarily mean the car is running lean it could in fact be running too rich if the 02 sensors are sending the wrong type of information to the ECU. How is your fuel economy? do you smell unburnt gas when you run the car? if so, it could be your 02 sensors faulting (if they are, they are telling the ecu its lean and your ecu is dumping to much fuel into your engine). If not, does your car idle low? does it try to stall? than it could be PCM related (if it didn't get the update) or it can be anything from bad gas to a bad airflow sensor to a leaking headgasket (worst case and probably unlikely). That is a difficult code to diagnose lol I'll leave it to the professionals of the forum to help from here.

ezone

^^^ That covered a lot of possibilities.


What Freeze Frame data was stored when the code set?

Grab a scanner.
What are the fuel trim values for STFT and LTFT?
Check if the MAP and BARO sensors match with the engine not running. If the MAP is out of whack, it can cause a false enrichment demand condition, leading to a false lean code.





Low fuel pressure can do it.
Restricted fuel filter could do it.
Easily checked with some fuel pressure testing.


I'll toss another one out here, a load of E-85 will cause a lean code too.


HTH

shawn101

hi ezone thanks for helping! i checked aftermarket header/exhaust for leak/crack but couldn't find any thing also checked and cleaned K&N Filter and one other thing i was using regular 5w30 engine oil and i changed to royal purple brand and using it since 2 month and i am thinking probobly got issue from the royal purple brand or ? and also engine sound a little different sound like buck buck/duck duck
here is freeze frame data 1/12
Fuel Sys 1 CL
Fuel Sys 2 NA
Calc Load(%) 21.1
ECT (%u00B0C) 90
STFT B1(%) 21.1
LTFT B1(%) 21.9
MAP(kPa) 25
Eng RPM 732
Veh speed(km/h) 0
Spark Adv(%u00B0) 5.5
IAT(%u00B0C) 51
TPS(%) 9.8

ezone

Ok, it was at idle, warmed up.
over 20% enrichment when the code set.
Rules out a fuel filter.
Doesn't rule out much else.
I can't convert the MAP value from kPa to volts though. I'm too used to seeing MAP read in Volts on my own scanner.
If your scanner gives live data, look for the other stuff I mentioned. Seriously look at the MAP vs. BARO values like I said, it's in a bulletin.

Also, what is the LTFT at a steady 2000 RPM in park/neutral with no loads? Closer to correct (0) or still around 20% off?

If you have a real header on it, is the primary O2 sensor mounted in a single pipe (reading only a single cylinders' exhaust) or is it mounted in the collector or on downstream where it can read ALL of the exhaust flow from all cylinders? (Reasoning: What if that one cylinder is firing poorly or running super rich? The other cylinders will suffer.)

Why do you think you need oil that is wrong for the engine? Shouldn't matter though.

Figure out the odd sound, it may lead you to your fuel trim answers.

HTH

shawn101

hi ezone i got freeze frame in USA form before it was matric form and yah o2 sensor is mounted on downstream pip where all four come to one! and i am not sure if it save to drive on engine light or not?

here is freeze frame data 1/12
Fuel Sys 1 CL
Fuel Sys 2 NA
Calc Load(%) 24.3
ECT (°F) 194
STFT B1(%) 21.1
LTFT B1(%) 21.9
MAP(inHg) 7.4
Eng RPM 732
Veh speed(km/h) 0
Spark Adv(°) 5.5
IAT(°f) 124
TPS(%) 9.8

ezone

Go check on the other stuff I already mentioned.

Fuel pressure check, MAP/BARO must agree at KOEO as described earlier, and the fuel itself.

shawn101

hi ezone the engine light is off now but i scanned it i thought the code is clear now but still have that p0171 code on and how do you check fuel pressure ?

ezone

The computer will turn the light off after a couple (it varies with the code) of drive cycles (specific conditions that enable the computer to run its self tests) where it no longer sees the fault. The code and its info will stay in the memory for a long time even though the light went off.

I could say that the computer doesn't see the problem right now, and to just drive it until the light comes back on. Then worry about it.
But I don't know enough about the car to say that with confidence yet.

Does your code reader give any live engine data? Can you look at the fuel trims while the engine is running? If it will, then warm up the engine and let it idle. See what the LTFT is.

I'm also looking for other clues that could explain the code, such as:
Did the light come on shortly after the last tank of gas, like within a few miles?
Did the car get run super low on gas, or ran out of gas?