CEL and crappy gas mileage

[jah81592]

po171 po174 is bank 1 and 2 lean codes! Your MAF could be the problem, but to me seems funny how when you installed the cai you had problems. I would look for vacuum leaks (a large one) in the intake tract between the meter and the intake. I installed a MAC Cai before my truck was turboed and never got any codes. Of course I have the SOHC, I wouldn't see any different for the ohv. I can't emphasize the importance of the meter in Ford's fuel injection enough and the slightest of vacuum leak especially after the meter will give you hell! Make sure you have all your silicone connections completely on all the joints and the worm clamps tight. I wouldn't suspect a meter prob because you didn't mention driveability issues. If you had a bad meter you would have extremely rough idle or no idle and stumbles,you name it. Ford's fuel injection doesn't work well without a proper working MAF!

 

[sparky2263]

I lost count how many driveability complaints were solved by cleaning the MAF sensor and replacing the oiled air filter with a non-oiled filter.

GM even released a bulletin concerning this. They will no longer cover driveability issues related to oiled filters under warranty.