Replaced complete distributor and now cylinder

I HAVE A 05 ASTRO AND I HAD THE SAME CODE PROBLEM P0303 IT SAYS CYLINDER MISFIRE BUT MY PROBLEM WAS THE COIL I REPLACED IT AND I WAS GOOD TO GO HOPE THIS HELPS GOD LUCK

TAKE IT TO NOONE ELSE BUT A CHEVY DEALERSHIP AND HAVE THEM RUN A DIAG GIVE YOU AN ESTIMATE. I LOVE THOSE OLD CHEVY ASTRO VANS I HAVE HAD 3 OF THEM. SIMETIMES IT IS CHEAPER TO JUST REPLACE THE OLD VANS RATHER THEN SPEND MONEY ON THEM. THE LAST VAN I HAD I HAD PUT OVER 700,000 MILES ON IT BEFORE I GOT RID OF IT.

number one plug has to be at TDC before you put distributor back in

You never take your vehicle to places like midas , pep boy's , firestone etc.. Find yourself a local independent repair shop . Po300 is a random misfire , not cylinder specific ! Causes ,lean air fuel mixture , vacuum leaks , low fuel pressure , clogged fuel filter , a O2 sensor problem . You need to find someone like this guy !
003 Scan Data for Fuel Code

I would check the rotor very carefully. They tend to burn a hole through the plastic under the center tab. It's hard to see sometimes. The spark follows that path instead of to the wire terminals. You may just want to try a new distributor cap and rotor.

Made in china? They send us ****. Try an OEM part. Costs more but they usually last for years, not months.

You may be out by one tooth on your new distributor installation.Try advancing or retarding by one tooth by removel and reinstalling distributor.I do not think there is anything wrong with your Cam position sensor. In fact I think it is trying to tell you that the gears on the distributor are not in propper position with the gears on the cam so give it a try and good luck.

Hi, the 4.3 liters have an injection system on them that can leak and will show up as a misfire. it is common but elusive to find. you might consider taking the van to a repair shop to have the problem diagnosed and go on from there.

THE FIRING ORDER IS AS FOLLOWS : 1-6-5-4-3-2.
CYLINDER NUMBERS (front-to-rear) :
LEFT (driver side) 1-3-5
RIGHT (passenger side) 2-4-6

To set ignition timing, ensure that engine is at operating temperature, (190 degrees or above), bypass EST (electronic spark timing) by unplugging the single tan wire with a black stripe from the distributor. Ignition timing should be set at 0 degrees or TDC (top dead center). If not, loosen distributor hold down bolt and adjust, then retighten.

Firing order on a six cylinder:

1-6-5-4-3-2

Hope it helps

Mike