Hello. Bought a 1998 Honda accord dirt cheap with 223K on it. Only had the EGR P0401 code in it. Ran good and can tell it was taken care of. Decided to pressure wash the engine as it did have a valve cover gasket bad and did tune up. Changed cap and rotor, wires and plugs. After 2 days of driving the CEL starting blinking and pulled the following codes: P0304, P0303, P01399, P0401

Since I have taken manifold apart and cleaned EGR passages, new EGR, replaced injectors. Clear the codes and fired it up. Immediately the P0304 came on and after few minutes of running it the P0303 came on. What do you guys think? Maybe a bad distributor?

 

If you have no records.
Pull the spark plugs and check for wear and proper gap, replace if needed.
Most likely the valves will need to be adjusted as well.
If the valves are too tight when the engine heats up the valves will hang open, this will cause loss of compression and a misfire. Readjust valves to bring compression back.
These two things will most likely be the reason for the misfire codes. This may be also for the insufficient flow P0401.

 

Thanks Mad Mike. I will do compression test next as you suggested. Do you think maybe the distributor is bad?

 

water might have gotten into the distributor, let it air out as well as for the entire engine bay in the heat or use a blow dryer on the entire engine bay for a few minutes

with so many electrical components in the engine bay i would suggest never spraying water onto it again

 

Nope.
Would not think that from the codes present.
Especially with how quickly the PCM popped out the 304 and 303 codes. Usually teh PCM takes it's time to put out such a specific code.

Verify no contamination in the spark plug tubes(oil or water)
Verify plug wires are not damaged/falling apart, or grounding out. (park in a dark area, leave engine running, open the hood and look for a blue glow around the wires, if so replace.)
Verify spark plugs are correct for application, gapped properly, not worn, and installed correctly.
Verify the cap and rotor are not worn out, contaminated, or carbon tracking(it will look like someone has used a pencil to draw inside the dist cap).
Verify valve adjustment.

I'm betting the valves have not been adjusted in a while, usually it is the exhaust valves that are tight. The valve seats erode from the exhaust gases. Intakes are usually fine or may even be a bit on the sloppy side.