Jim Grant's Tech Tips

’96 Honda Accord EX, Unfixable Computer Codes

Q: My ’96 Honda Accord EX has a MIL that reads these codes; P0301, P0302 and P1300. I've been doing the process of elimination by replacing spark plugs, plug wires and rotor cap, the rotor itself is still good. I even replaced the PCV thinking it could help. I put some fuel injector cleaner hoping that could help clean the fuel injectors. The thing about it is, the car runs great! No hard starts, no hesitations, no smoke on exhaust, it just starts and goes. But, the light still comes back on after I clear it with the scanner after I replace something. I've asked folks and checked online forums for similar problems and so far I have yet to get the problem solved..

Thomas

A: That’s the funny thing about those computer misfire codes, an engine can seem to be running just fine but if the computer isn’t happy with what it is seeing, it gets fun. It sounds as if you’ve covered most of the basics and commonly known reasons. But, if replacing all those parts didn’t reach the end goal you know your not dealing with the norm. You should know that other items can set misfire codes that would at first glance have not a thing to do with the ignition or fuel system. One item that would be helpful is if your code reader has freeze frames you’ll want to look at that information to see just when and what condition the misfire codes are set in. At low RPM and engine load items such as idle air control valves, manifold pressure sensor or EGR valves can set misfire codes. Fuel pressure and delivery issues will tend to set codes when accelerating or at higher speeds. Then carbon deposits can create another misfire condition. That’s just some of the fun you can have when something other than ignition issues are setting misfire codes. Computers will have you chasing your tail. Information and a different strategy is called for when the codes just keep coming back and nothing seems wrong.