I have a 97 civic that is running rough. I hooked up a scanner and it is saying that all 4 cylinders are misfiring. It runs pretty smooth and runs fine. Anyone know what i should try to check?

 

Spark plugs? I would pull them and inspect them for carbon deposits. I am sure some other members will be able to chime in with additional help. Is your timing correct?

 

Plugs could be the issue, but also plug wires. Do you know if either have been replaced in recent history?

 

Try using new NGK spark plugs make sure not to cross thread them.
Also use new wires too. should clear up your problem

 

Plugs and wires were recently changed with KGK plugs and wires. Timing is correct on it. Car has about 206,000 miles.

 

Is it worse at idle or when trying to drive? Abnormally low idle speed may be interpreted as misfiring. Check the valve adjustment a valve too tight will cause misfiring particularly at idle. Also do a compression test in case there's compression loss for other reasons. Misfiring under load (heavy throttle, low rpm) points more to weak ignition. Could be the cap, rotor, or coil if the plugs and wires are OK. Misfiring at high rpm and heavy throttle is when the fuel demand is highest, could be a clogged filter.