waulen2980

Switched back from custom tune to stock to pass smog out here in Cali. That seemed to open the can of worms because it subsequently caused the p0171 code. Broke down and took to mechanic and they replaced air intake and and o2 sensor. That still didn't do the trick so they wanted to charge me another $300 to replace MAF sensor. I told them no and ordered one myself since they are easy to install.

After I install that, if I am still throwing the system too lean code, what else could it be?

Thx for help!

petrock

Vacuum leak. Good luck...

cariacou

I have the same issue with my steeda cai + brenspeed tune. the MAF is totally clean, I don't think I need to do anything to it.

I have both p0171 & p0174 lighting up. do you have p0174 too ?

my dealership blames it on my custom CAI unfortunately

petrock

Your issue is probably also a vacuum leak, except it is probably between the upper intake and the MAF sensor in your case since you have codes for lean conditions on both sides of the motor.

waulen2980

Replaced the MAF sensor and that seemed to fix the issue. Now I just need to figure out why my emissions are out if whack so I can pass smog test.

Do you think fuel filter and spark plugs need replacing already- 2007 mustang 78k miles

cariacou

you mean the Steeda CAI tube that links the MAF to the engine intake ? I checked this very carefully and all connections were well sealed