Expert: Sean Halliday - 11/16/2008

Question
I took my car to the autozone and had it put on the reader and here is what came up. P0305-PCM determined misfire #5cyl,P0170-PCM determind fuel compensation valve for bank one exceeded specified range. P0173 comp valve for bank 2 exceeded specified range. P0300-multiple random misfires. The car has 99000 miles on it. Where do I start? Could the air mass flow sensor cause most of these problems?

Answer
Yes the 170 code is common for fuel trim failure.Weak or rich mixture will result if the maf is going out.If your car has big mileage,its a good idea to renew the o2 sensors also.The o2 sensors before the cat.As these maf sensors are expensive its best to have it diagnosed by a shop with the proper scanner,it will read out if it is faulty.Incorrect fuel mixture will cause misfire in all ranges of cycle and can cause serious engine damage if not corrected.