I own a 1998 Mazda b2500. Engine code read misfire on cylinder four. The misfire is intermittent. while driving it is significant enough to shake the whole cab. I could also smell gasoline burning in the exhaust when the misfire first came up. I started first by checking the spark to the cylinder on both spark plugs. The coils to the wire, wire to spark plug, and spark plug produced a spark. Second off, I replaced a single ignition coil. I did this because when the two ignition coils were swapped, the misfire changed from happening at high RPMs, to happening mostly at idle. When the coils were the other way around, it was the opposite. The coil seemed to have helped the issue, but the misfire persisted. Third, I decided to replace both spark plugs on cylinder four, which did not solve the issue either. Fourth, I performed a fuel rail pressure test. On the drive the PSI readout was consistent, and at a reasonable PSI that I cannot recall. I may have seen the readout move slightly, about 2 PSI or so, down then back up while the misfire happened, but I feel this is negligible. It would have only moved around 1-3 times, only of course if this was not my eyes playing tricks on me. I am apprehensive about putting another new ignition coil in because of the steep price. Does anyone have advice on how find the cause of this misfire and fix it?
