i got a 98 blazer with a 4.3 vin w and i cant seem to get the timing right on i replaced the timing chain and sprockets, turned the engine by hand to make sure the marks lined up right and they did so then i put it all back together and set the number 1 piston up and set in my distrubutor it lined up with the 6 and started right up but when i checked it with the scan tool it was at +30 to +35 degrees. so i tried moving it back a tooth but now it idles all rough. do i need to do that crankshaft relearn thing even though i didnt replace the crankshaft sensor?

 

The timing cover should not be reused, it needs to be replaced.

If/when the crankshaft position sensor or timing cover is moved, removed, replaced, or disturbed in any way, the crankshaft position sensor relearn must be performed.

If the distributor is NOT installed correctly, DTC P1345 will be in memory and the SES light will be on. If that's what you've got, check & adjust camshaft retard, that will put ignition timing where it needs to be.

 

+1, this link should help you out:

https://blazerforum.com/forum/tech-articles-diy-29/edi-engine-timing-24373/

 

thanks guys