Okay straight to the point. Ive recently been experiencing extreme misfires with my 1997 honda civic. So far ive changed out the spark plugs and wires and it had no effect. I seafoamed it and still got nothing. I took it to autozone to find the codes that came up were P0303 P1491 P0401 P1300 P0302 P0301 which i know are misfires from cylinder 1-3 and insufficient flow and lift. Would replacing the egr fix/cause this or could it be something else?

 

EGR system will clog up with carbon, which can be cleaned out without replacing anything. This causes codes and high emissions, but usually not misfiring. Compression and valve adjustment should be checked. Inspect the distributor cap and rotor for cracks or just replace. The HX is sensitive to an O2 sensor that has gone out of spec (even though it may not throw a code) or the wrong type. Consider that if misfiring occurs only after warmed up.

 

Okay so I've recently replaced the cap, coil, wires, sensors, and cat. I haven't been able to check for misfires since I overtorques a valve cover bolt. I'll post results once I get the car up and running again.

 

So it's running. It was still misfiring a lot but then went away. I also decided to change out my tubing for my ram intake as well and motor mount while waiting. The misfires seem to come and go but it's almost not even present anymore. I'm still going to go through with adjusting the valves and see what happens after that

 

Okay so I decided just in case to check my injectors by pulling the connectors one at a time after letting it idle for about 10 minutes and every single one changed my engines idle pretty low so I know fuel isn't a problem. My entire exhaust from the manifold all the way back is new including the o2 sensors (1 is a wideband and the other is narrow) I've practically changed out my my entire ignition system from the rotor to the plugs, and tube seals. The battery is new the ram is new.

 

So after Running seafoam through my gas tank the misfiring is practicially gone. I dont know where the clog was but it has fixed it. Thanks for the replies