I have a 2001 Mazda Tribute with 86,100 miles on it. The check-engine light came on recently, and stayed on. In addition, the car would stutter and almost stall at 1500 RPM or lower. I took it to a local shop and they pulled the code, which they said was "B303" or a misfire on cylinder 3. Has anyone run across this before, and if so, how was it resolved? My local shop told me that they would have to take apart part of the top portion of the engine to get to the cylinder itself, before they could figure out what was causing the code in the first place.

 

With that many miles and that error code I would look at simple stuff like spark plugs and wires. The platinum plugs last at least 75,000 miles and do wear out. My Taurus cylinder misfire code was cleared with new plugs. I replaced the wires since they were old as well.

 

Well, looks like you have a Typical Coil pack going bad. Po303 is the code for the Misfire. If You have the 3.0 L Eng you have 6 coil packs. One pure plug. Now for the bad part the 3 plug under your intake manifold. Will have to be removed to replace your plugs and coil packs . I recommend since your having to remove the intake, replace all three plugs and coil packs.