Expert: autohelp - 4/3/2010

Question
QUESTION: I am having a problem with the air to fuel ratio. What would cause a 22 to 1 ratio? it is supposed to be 14.7 to 1. Replaced throttle body sensor, tried another throtle body with injectors, checked the fuel pump it is giving a constant 10 lbs/ of pressure as it should.

ANSWER: IS or HAS the check engine light on the dash ever illuminated while driving the vehicle ?.

---------- FOLLOW-UP ----------

QUESTION: Engine light does not come on. What determines the air/fuel ratio? What parts are involved? How can it be adjusted? I replaced plugs and verified the distributor is working properly (a mechanic checked it)

Answer
Fuel ratio is determined by the oxygen sensor and the computer.

Since the fuel ratio is calibrated to operate as an 8-6-4 engine, I am NOT surprised that the fuel ratio is a little high while in 8 cylinder mode as the vehicle was not intended to run on all 8 cylinders at all times.