Plugged air filter?
crazy- truck ran like garbage - Check engine light on - I have 3 testers... only 1 picked up on a code P1131... O2 sensor running too lean ... recommended to check out for broken vacuum lines ... did .. Sprayed carb cleaner onto of intake .. got to air filter .. truck ran better .. removed air filter and truck ran great ... installed new filter ... back to running like garbage ... checked for mouse nests ... tube seems clear... any idea..
Shooting at the hip here .. but I am wondering if intake is not partially plugged up internally and without any restriction it runs fine ... but with a filter in it the motor struggles to hard to breath ... kind of like a heavy smoker in a respirator... He breaths fine when the respirator is off but the minute you put it on him ... he does not have the lung capability to pull in the proper air he needs to breath correctly