Long Term Fuel Trim at 20% 04 Mazda 3 2.3L

[00scrub]

When I get time next I feel like I need to test the FP, intake runner solenoids, and purge valve solenoid. All the data I've seen is showing that the O2 and MAF look to be operating normally I think.

Marcozi, I don't think there is a vac leak. If there was wouldn't there be a large FT offset at idle? This only happens under load.

 

[wtd]

Have you looked at fuel trims at higher rpms? Take it up to 3,500 rpms or so and look at your fuel trims. Typically, if they get better and close to normal, you have a vacuum leak. If not, it may be a MAF or low fuel pressure issue.

 

[00scrub]

I checked the Solenoids and purge valve and they both function with 12V applied and move the actuators. I'll have to go get a pressure test kit for the fuel pressure. Anyone know if I can use normal fuel line and a hose clamp in place of the quick release connectors on the fuel lines for the test kit?

 

[00scrub]

Took more measurements at hwy speeds and loads when going to get the fuel test pressure kit from Autozone. The increase in LTFT is load dependent and not just RPM. It was already at 20% at 3000RPM at 45mph and approx 70% load.
Is there anything that could cause a vac leak at such a high load, but not at idle?

 

[00scrub]

Did the Idle, and 3000RPM in Park fuel pressure test and it came out OK (~55PSI). The rev to 3000RPM only got it to 20% load
Does anyone know if I can read fuel pressure via the OBD port on a 2.3L Mazda 3? It would help me be able to check it under load.

I'll check the plugs when I get the chance, and then if I'm still stumped I guess I'll parts cannon the sensors and fuel pump.

 

[thescreensavers]

While at idle, Plot Short term fuel trim on your scanner let it stabilize. Now take brake cleaner/carb cleaner/start fluid which ever you have and spray around your intake start to finish past your MAF. If you see any big changes then you found a leak

 

[D60]

Did the Idle, and 3000RPM in Park fuel pressure test and it came out OK (~55PSI). The rev to 3000RPM only got it to 20% load
Does anyone know if I can read fuel pressure via the OBD port on a 2.3L Mazda 3? It would help me be able to check it under load.

I'll check the plugs when I get the chance, and then if I'm still stumped I guess I'll parts cannon the sensors and fuel pump.

I think your fuel pressure is fine, but can you just power brake it?

On a '98 CRV I somehow fed the hose out the hood at the cowl and laid the gauge on the windshield and went for a spin. True story.

 

[00scrub]

Got some more diagnoses done and I think I solved the issue. The MAF sensor was bad. It was flat-lining above a certain load causing the LTFT to spike up. With the new MAF sensor the LTFT jump up to 20.3%, but the STFT shows -20.3% so I think it'll take some time for it to adjust the learned values.
Thanks for the help y'all