Hello Scotty.... thanks for all you do... I have a car matter and was wondering what your opinion would be. I have a 2001 Mazda Millenia 2.5L and it is throwing engine code P0304 (Cylinder 4 Misfire). I have swapped that plug with another and retested and swapped that wire with another and retested and the same cylinder continues to be misfiring. I did a compression check and that came back good. [.. when starting the engine, the idle goes up as normal and then drops back down to about 800 and then the code comes up... and you can feel the engine is running rough...] This particular engine does NOT use coil packs, but rather a distributor, so I changed the cap and cleaned all the carbon off the rotor (autozone did not have new on in stock). Still the same problem. I listened to all the injectors via the screwdriver to the ear method and the tick tick tick-ing of 4 is the same as the others... so it is firing... (though I know it could be clogged)... Last week, before I tried changing the distributor cap this weekend, I ran it down to a quarter of a tank and put in a bottle of the Lucas fuel treatment and fueled up with 93 and took it on the highway and hit it as best I could.... but still having the problem. While changing the cap I had the air assembly apart, so I cleaned all of that out, including the MAF. Also I had gotten codes on the VRIS (Vehicle Resonance Induction system), but I tested those and they came back as good.... and if air was a problem I would expect to either get a lean or rich mix code... not a misfire.... Do you think the computer could be mistaken in the cylinder is saying is misfiring? Or have you any other ideas? since the only way at these injectors is via removing the plenum, I thinking of purchasing the tool to run the cleaner through the rail and see if that does it.... but want to discuss this with as many pro's as I can before making any more moves... Thanks for any insight you can provide.... really appreciate it.... Thanks Matt Montalto

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swap injectors next to see if that's it. But do try cleaning first