2003 z with 85000 miles. Took for a spin today and cel started blinking and car started missing. code reader says p300 and p303. I know what the codes mean. Got on web sites and everybody has got a different fix. Some say plugs,coils, injectors. Checking to see what everybody on this site did to fix their's. Thanks.

 

It could be any if the things you listed. You said you know what the codes mean but just for ease of reading I'll mention it too. P0300 is random/multiple cyl misfire and p0303 is cylinder 3 misfire.

You need to look specifically at cylinder 3 to try to find the problem. Pull the coil out and swap it with cylinder 5 for example. Then clear the codes and go for a drive. If you get p0305 that's a cyl 5 misfire and you know you need to replace that coil.

Check your plugs.

I dont think you can reach the injectors with a stethoscope or a screwdriver up to your ear to hear if the injectors are firing on the vq unless you have an aftermarket Intake manifold. That's the best test I know of with basic tools and the injectors In the car.

Unfortunately the car can't just Come out and say "excuse me, sir, but I have a bad coil in cylinder number 3. Could you please get that fixed?"

 

Here's some good info on the codes.

0300

http://www.engine-codes.com/codes.php?code=p0300_nissan

0303

http://www.engine-codes.com/codes.php?code=p0303_nissan

 

I had this ... I disconnected the battery ( to clear old codes ) moved the " #3 coil pack to 1..... started her back up.... code moved... replaced that coil pack ... done deal.

 

Found oil in spark plug tubes #3 and #5 and around valve cover tube seals. Had new valve covers i got last spring.Just havent had time to change them.Put them on today what a pita.Going to put new plugs in and new coils and check fuel injectors and have them clean. Don't want to do this again for a while.Need to clean intake, it has light coat of oil. When i took valve covers off the inside look clean,no motor honey. Well thanks everybody!