What cause misfire on cylinder #3 & #4?

what cause misfire on #3 and #4 cylinder I replace #3 coil no change made I check for pulse at 3 and 4 injector with a noid light the light flash and injectors are clicking.engine codes are P0300, P0303, P0304. compression #1, cylinder 195psi, cylinder #2, 190psi cylinder #3, 185psi, cylinder #4, 190psi.

Good job checking the compression, lets remove the spark plugs for inspection. We need to see what color they are so we know in what direction to go in the make the repair. The fuel injectors maybe getting a signal but if the injectors are bad/clogged it wont make a difference. Please unload images of the spark plugs so I can see them. Also here is a guide and video which can help in the meantime.

https://www.youtube.com/watch?v=QTE8k06MzwQ

and

https://www.2carpros.com/articles/engine-misfires-or-runs-rough/

Please go over these guides and get back to us.

You may have a PCM that is bad, lets check the injector pulse and power feed, this guide will show you how.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector/

You should have 12 volts on one of the injector feed wires for each injector . Let us know how it goes

12 volts at the injector feed wire with key on

That is a good sign, did you go over the guide above to check the injector pulse?

yes i went over the guide. i have injectors pulse but sometime on injector #3 my noid start blinking and then stop and start back.

This can be a wiring problem or the PCM is bad. Did you look at the wiring yet? This guide can help.

https://www.2carpros.com/articles/how-to-check-wiring/

Please go over this guide and get back to us.

misfire on #3 and #4 cylinder i replace ignition coils and spark plugs i check compression #3 185psi #4 190psi when i check for pulse at #3 fuel injector the noid light flash stop and flash while engine running what is causing theses problem? the engine codes are p0300, p0303 and p0304.

It sounds like the ECM is bad, I would get another one which should fix the problem.

when i check the trigger ground signal from the PCM i connect the clip end of test light to the positive post battery and the other end to the signal wire on injector while engine running the test light blink stop blink stop and so on. i check the signal wire from injector to PCM i find no break in wire.

So it sounds like the PCM is working, does the other wire of the injector have power when the key is on?

yes the other wire have power when the key is on, why the test light don't constantly blink at all time when doing the test? and why my noid light don't constantly flash at all time when doing the test at #3 injector?