Scotty I have a 2002 Honda Civic lx 1.7l I'm having fuel trim problem my long-term fuel trim is 7% and my short-term fuel trim for both sensor 1 and Sensor 2 is all over the place how do I fix it
Well it's adding fuel which means the vehicle is running lean so my advice would be look for vacuum leaks pray you've got a vacuum leak of course it could also be a weak fuel pump clogged fuel filter dirty fuel injectors but more often it's vacuum leaks
I sprayed a whole bottle of carb cleaner on the engine and nothing happend
What are the fuel trims at idle ? And what are the fuel trims at WOT? That will help point us in the right direction. At idle I would be looking at vacuum leaks first. At WOT I would be looking at a dirty/bad MAF or fuel pressure.
I meant if the fuel trims are lean at idle suspect vacuum leak. If the fuel trims are lean at WOT suspect fuel pressure or bad/dirty MAF.
There no leaks I sprayed the whole engine with a whole bottle of carb cleaner and nothing happened it was just bubbling on the Hotspot where is the mass airflow sensor on a 2002 Honda Civic anyway I might have to change that or could it be because of my Chinese catalytic converter that doesn't work right I live in West Virginia and they don't care about the Cadillac converter
If there are no vacuum leaks. I would hook up a scan tool and look at your freeze data and see at what rpm and engine speed that code is setting. If it’s setting above 2k rpm’s or higher speeds you my have a struggling fuel pump not supplying enough fuel at higher RPMs or a fuel pressure regulator. Nonetheless freeze data helps narrow down your next troubleshooting. You’ll need a fuel pressure gauge to check fuel pressure and I believe you Honda needs a special adapter that goes on the fuel rail to check the fuel pressure.
Would that make it run lean and when I hit the it seam to go about normal and at high speeds 80+ seems to do better
Yes, low fuel pressure or volume could make it run lean. If the ECM is getting a full rich command but the pump is struggling to send fuel the o2 will see lean mixture and setting a fault. Again, freeze frame data is important to see when that code is setting. Once you have that data you can try and recreate it and look at live data and see what’s going on. Without scan data you could throw parts at it and see what sticks, but that’s not how diagnostics work.
Forgot to mention that a faulty a/f sensor could also be setting a p0171. You would see it on scan data if stuck lean by looking at the voltage of the 02. A working a/f should be switching between .1v to .9v
@th3kr1s said what are they at idle, what are they when reving. Rev it up for 10 to 20 seconds to 1500 to 2000 and write down the trims. Let car sit at idle for few minutes and write those numbers down. Report those numbers back to us. Stft jumping around isn't anything to worry about. Running lean has many causes, here are most. Vacuum leak, fuel pump, fuel filter, plugs, wires, coils, injectors, valves, timing, map,maf, throttle body, pedal position, gaskets, IAC, coolant temperature sensor, catalytic converter, o2 sensors. This is most of them, some are least likely and some are most likely. Now the fun part is figuring it out. When checking for vacuum leak if you don't have a smoke mechine use propane. Just turn on gas only and move it slowly across engine and all vacuum lines. When you find the leak the engines tone will change. Also have scanner hooked up and look at trims. When you find the area they will richen up.
short-term fuel trim for both sensor 1 and Sensor 2 is all over the place how do I fix it
For the O2 sensors, you should check their voltage reading.
What should my voltage reading be at
Generally, the reading should be between 0.1 and 0.9 volt and by revving up the engine, it should go up.
My voltage is good then
How about some codes to start with? And mileage?
P0420 and 172000 and when I took it in to ntb for an oil change they said it sounded great
P0420 is bank 1 CAT below efficiency. What is ntb? Something wrong with your fuel system is causing the CAT code. Air filter, MAF, injectors, fuel filter, fuel pump, MAP sensor, etc.
National tire and battery
I got the exhaust manifold and catalytic converter for $70 its all in one together
I sprayed the whole engine with a whole bottle of carb cleaner
Bad idea. Carb cleaner will pollute the MAF sensor.
