I have a 2005 Hyundai Sonata 4cyl. and have a misfire problem with the 1st cylinder. I’ve had it pressure checked and there isn’t a problem with the cylinder, such as a ring or warping problem. I’ve replaced the wires, both boots, both ignition coils and the plugs twice. I was told I need to replace the ignition coil again but I wonder if there is something that is making the coil go bad. I’ve also replace the throttle position sensor and both O2 sensors. I had the front catalytic converter replaced because it was bogging down and very slow. It still runs rough and the check engine light is on. I was told also that I need to replace the engine speed sensor. I bought the car in Oct. of 2004 and only has 68000 miles on it. Any help would be greatly appreciated.
Has anyone thought to check the fuel injector for Cyl #1? A clogged, dirty fuel injector can lead to a lean burn miss that could be mis-diagnosed as an ignition problem. A run of a professional injector cleaner could fix this problem.
Another thing that can cause a cylinder misfire code is a dirty/defective Mass Air Flow sensor. You can try removing MAF sensor and clean it with an aersol MAF sensor cleaner to see if it eliminates the misfire code. If that doesn’t work, have a scanner that can do real-time diagnostics connected to the computer. Take the vehicle for a drive, and while monitoring the throttle position data along the with mass air flow data, push the accelerator all the way down to the floor for a moment. Now compare the throttle position data to the mass air flow data. If at 100% open throttle the mass air flow sensor measures something other than 100% mass air flow, there’s a problem with the MAF sensor.