P0171 Headache
 

I have had this 2001 civic lx for a bit. First car and I wanted to fix it up.

I have been dealing with the code p0171 Bank 1 lean.

I have not been able to fix the issue. I live in Las Vegas and it is too hot to work on the car. I have to know where to start so I can at least cut down on the time it takes to fix this car in the heat.

So far, I have put new sparks, new o2 sensors both NGK/NTK. I had some spare parts around and I replaced the FTP sensor and the Evap Solenoid Valve next to it. This fixed a previous code that intermittently appeared, p0453. Although I am not sure if it was because I changed the o2 sensors or the FTP.

I have put a new air filter on it.

I have a spare MAP sensor that I will try to put on soon.


Now here are some symptoms. Car never starts on the first crank. If the car warms up, it will start instantly. Say I turn of the car and then crank it again, instant start. Fuel Meter is off by plus or minus 2 ticks. Car idles fine but sometimes get a little bit shaky randomly, not too bad but it happens sometimes at stop lights. I changed the motor mounts except the rear one. That might explain it but I am not entirely sure.

Also the throttle response is not entirely linear, Sometimes it feels like the car is weak but it is not too noticeable.

I am thinking it is a fuel issue. I want to replace the fuel filter since I think there might be some blockage. I suspect this because my a previous code was p0453, high voltage in the FTP sensor. Any input is appreciated. :)

Re: P0171 Headache
 

Got freeze frame data to go with this code?


What's the fuel pressure?
What is the pressure while it acts up?

What kind of fuel are you using? (You can't burn E-85)

Got a scanner that can display live operating data?

Re: P0171 Headache
 

I have a Bluetooth ob2 that can read live data. But fuel pressure is not one available on the apps I use.


If anything, I might be able to rent some tools from auto zone to check the fuel pressure.

Re: P0171 Headache
 

Fuel pressure can't be read in the data, you have to open a fuel line to test directly...and you may need to leave it connected and have the gauge placed where you can see it as you drive around so you can check when it acts up.

Re: P0171 Headache
 

I am going to be replacing the fuel filter and strainer in a few days. I have all the symptoms of a partially clogged filter. Hopefully that will fix the issue. If not I am going to fully test it out. It is about due for a fuel filter change so I might as well.

Re: P0171 Headache
 

I replaced both and now the car doesn't crank. But jot because of the filter.

The car primes and everything. A little fuel comes out when I turn the acc on.


But when I crank, fuel does not spray out. So the car doesn't start. No fuel comes out at all when I crank.

Re: P0171 Headache
 

You just had the pump out of the tank and replaced the filters?

Now there is barely a trickle of fuel when you turn the key on?

I'd guess at least one of the lines inside isn't fully seated and is leaking or a seal was lost, dislodged or damaged and is leaking.

Re: P0171 Headache
 

I disconnected the fuel line up top to see if the pump was pumping.
If I turn on the switch to the ACC posi tion, the pump runs and primes. It will give out a trickle of fuel. But fuel does come out in a decent amount for that 2 seconds.

Now when I crank the car, there is no spray at all. No fuel at all comes from the line .

So it appears that the hoses and connections are good. And that the pump works to some extent. But the fuel pump is not spraying when I crank the car. It us priming and the pump does run, just not when I crank the car.

Re: P0171 Headache
 

I might go and continue testing the four circuits at the fuel pump relay.

If any of the four circuits at the relay is not doing what it should, that would point me in a direction for the next test.


Wait, the starter DOES crank the engine, yes?

Re: P0171 Headache
 

I just put a new relay in and the same issue is happening.


But this time fuel actually comes out when I crank it. It is around 1/4th to 1/2 the amount that comes out when I prime it.

By cranking I mean that the car makes the noise but it never starts. Like the starter is running but it never sparks because I don't think there is enough fuel for the car to start. I primed it over 20 times hoping it would give but it never does.

I'm starting to think it is the fuel pump.

But that doesn't really explain why the car worked before.

Re: P0171 Headache
 

Tossing parts is not diagnosis.


A real fuel pressure test might be in order to prove if pressure is within specification or not.


Testing could prove or disprove this theory.

Re: P0171 Headache
 

If you have a spray can of carb and throttle cleaner (very flammable) you could squirt a little into the throttle body and crank it over, if it fires and tries to run for a second this would confirm it's a 'lack of fuel' problem.

Re: P0171 Headache
 

Like the original thread said, the system is too lean. It might be an issue with the actual fuel pump not putting out enough fuel.

I am not completely sure about this and I can do any further diagnosis due to a lack of tools.

I am pretty sure one of my family members has some extra parts lying around, hopefully a fuel pump. I will try that out tomorrow.


But what has me stumped is that is how when priming, a lot of fuel comes out and when cranking, a quarter for the priming amount comes out.

Re: P0171 Headache
 

Disconnect the fuel pump wire harness and provide 12 volt from the battery. You should hear the pump working . start the car