I have a 2005 Pontiac Vibe with 130,000 miles. I was checking out the Fuel Trim numbers with my scan tool and found that the LTFT values were 3.1% at idle and 10.9% under load when driving at 60 mph. The STFT values remain around 0. I just cleaned the MAF sensor and throttle body to see if the LTFT values would improve. I have driven one time for 30 minutes so far but the values have not begun to correct. Any insight would be greatly appreciated.
So far there hasn't been any improvement in the fuel trims. The LTFT is still around 3% when warmed up and idling and maxes out around 12% when opening the throttle. The absolute throttle position at idle is around 15% which I've read can be normal on these Toyota ZZ1-FE engines. I will replace the intake manifold gasket next since that seems to be a common problem. Would a leak at the IM gasket create the conditions I'm describing?
Try a bottle of Techron fuel system cleaner. 10.9% LTFT means that the ECU is adding extra fuel to correct a lean mixture longterm. However, your STFT is good at 0%. It could be some dirty injectors causing a lack of fuel, so give the Techron a try first.
Keep in mind that -10% to 10% is acceptable with 0% being perfect.
Thank you Razmig. I will give it a try and report back.