Rep Power: 0

I have an 01 EX going on 70K miles that's bone stock except a K&N air filter. I took the car to Autozone and had them scan the ECU and it came back with code P0171 "System Too Lean". The light will sometimes go out for a little while but then comes right back on. I have made sure the gas cap is wrenched on tight as to eliminate that being the problem. Open for ideas as I'd like to avoid taking it to a dealership if I can.

 
Rep Power: 811

You're not getting enough gas into the engine. Try a good fuel system cleaner and see if it goes away.

 
Rep Power: 0

My last fillup, I put some Chevron Techron fuel system cleaner in and the light went out after a couple trips, but is now back on. Should I reset the ECU after this tank of gas is used up?

 
Rep Power: 0

i would take it to the dealer and have them look at it. Of course they will give u some BS so u can try to reset it and if it stays off then it might be okay. Usually if u reset it and it comes right back on then u know the problem still persist.

 
Rep Power: 811

Chevron techron does not work. Believe me I know after looking at my pistons and cylinder head.

 
Rep Power: 0

Gearbox, do you have pics of those dirty pistons?

 
Rep Power: 305

have you changed the fuel filter?

 
Rep Power: 423

It could be a lot of things. You could have a clogged injector, a bad O2 sensor giving a funny reading, a fuel filter gone bad, lots of things could have caused it. I'd take it to someone other than Honda. Find a private mechanic you trust. It'll save you the trouble of getting the Honda run-around.

 
Rep Power: 0

Sounds like a clogged Fuel system like Gearbox said. Go to a shop and have them clean your fuel injectors...It costs around $50.

PO171 - Fuel Trim System Lean (Bank 1)

 
Rep Power: 0

I never have changed the fuel filter. Isn't it located in the gas tank and a real pain is the *** to change?

One other thing I forgot to include, is that immediately after the light comes on, the car begins to lose power when accelerating and compensates by shifting really weird.

I think I'll probably end up taking it to a local mechanic.

 
Rep Power: 811

Well when the engine light comes on, nothing is working right. That's why the power goes away. I would just get it looked at so they can diagnose the real problem.

 
Rep Power: 0

Thanks for the help and suggestions everyone. Looks like I'll be hitting up my local mechanic.

 
Rep Power: 305

If no other trouble codes are listed:

1. Check the fuel pressure.
If the fuel pressure is too high: replace the fuel pressure regulator.

If the fuel pressure is too low: check the fuel pump, the fuel feed pipe, the fuel filter, and replace the fuel pressure regulator.

IF the fuel pressure is okay.
2. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or Neutral) until the radiator fan comes on.

3. Check the primary HO2S (Sensor 1) output with the scan tool.

If it stays at less than 0.3 volts or more than 0.6 volts replace the sensor.

If not:
4. With a vacumm pump, apply vacuum to the evaporative emission canister (EVAP) purge valve.

If it holds vacuum, check the valve clearances and adjust if necessary. If the valve clearances are okay, replace the injectors.

If not, replace the EVAP cannister purge valve.


Fuel pressure should be 40-47 psi. The most likely, cheapest, and easiest thing to fix, would be the fuel filter.

 
Rep Power: 285

put back in a paper filter if its a drop in k&n, or put the stock air box back in if its an aftermarket system, problem solved

 
Rep Power: 811

Intake should have nothing to do with it. Even without an intake the car should work fine. Ronin, here are the pistons at 24k miles, but this was AFTER we scrubbed them with brake cleaner. It was alot worse before. I used some greased lightning fuel treatment that's supposed to be super good. Maybe that might help.

And omg! I need to take pics of my stock header. The holes are about 2mm smaller due to carbon buildup. I was shocked.

 
Rep Power: 285

intake has a lot to do with it. you have a free flowing intake system your gonna get more air into the engine. below wot it wont be much of a problem because the ecu can adjust, but at wot and the ecu is just running open loop, the ecu doesnt know to copensate

 
Rep Power: 583

so what caused ur carbon build up?

 
Rep Power: 0

Wow Gearbox, that is truly nasty stuff....

I don't see how my drop in K&N air filter would make any difference. My car ran perfect for the last 20,000 miles with the K&N in there. Anyhow, my car is now playing games on me. The light will come on and go off at random. Sometimes I can go over 100 miles with it off then it just comes on out of nowhere. When the light is off the car runs like a dream but the second the light comes on, it has less power and shifts different. This problem is really getting annoying.

 
Rep Power: 0

hey im having the same problem but my ligth stays constantly on and my car only has 13,000 miles is a 2001 dx i trhink that my problem came up after i put octane booster what you guys think

 
Rep Power: 0

I work at my local Honda Dealership. We have cars come in all the time because there gas cap isn't tight enought. That might fix some of the problems on here.

And when I write up there complaint if the car isn't in warrenty it costs 80 bucks. And that is just to tighten the gas cap.

 
Rep Power: 0

hey thanks man i just realize it sait in the tank cap but do you think that the octane booster might be the problem. also for some reason i have a chirping noise in the engine area when the rpm is about 3000 and 3500 range. any clue

 
Rep Power: 0

I have no clue what the chirpping noise could be. If your car is still under warrenty just take it to them. Any dealership will fix it for ya.

 
Rep Power: 0

hey man my warranty just ran out and this car only has 13000 miles on it im station in italy and because is us. specs they dont want to touch the dam car

 
Rep Power: 0

eww then for a honda tech to look at it, it will run you 80 dollars to do a diagnostic plus the price of any needed parts.

 
Rep Power: 0

anyways why don't we stay with the original post and try and help this dood.. i have the same problem with mine except i have misfires constantly in multiple cylinders P0302 and P0303. Everything checks out otherwise on my scantool, i am cleaning the EGR valve tonight to see if that makes a difference as that seems to be one of the biggest problems with honda engines from what i can see on the internet

 
Rep Power: 285

what kind of plugs are you running and how old are they

 
Rep Power: 0

Denso iridium, 1 month old. I cleared the codes and will keep going until this happens again.. its almost always on startup for some reason.. could be an over sensitive system.

Anyway if i had Honda's mode 6 test codes i code test the EGR without even taking it off...

 
Rep Power: 305

I also got a CEL this morning while driving my car. It has 86k miles on it, 01 sedan LX. But, the thing is, I have NO CLUE whats wrong. I was just driving regularly on local streets, when I happend to look at my speedometer, and noticed the CEL was on. I pulled over, popped the hood, checked for any leaks, smell, smoke, or anything like that, and found nothing. The car still runs exactly the same, so I dont know what could be wrong? Any suggestions?

 
Rep Power: 285

probably didnt tighten the gas cap enough. tighten it a few more clicks, and if that was the problem it will go out in a few days

 
Rep Power: 0

did you by any chance put a new muffer system if so check for exhaust leaks that happened to me and now is good