My 2000 blazer ran fine, had to replace the battery, now when I start it up it run rough. Code tells me I have multiple cylinder misfiring. Can anyone give me a hint. Thank you

 

How do the plugs look? Are they AC Delco plugs? Wires and all are good? Is the check engine light on?

 

how many miles are on it? when was the last time you replaced the plugs and wires? have you replaced the distributor cap and rotor? could be that the camshaft position senor is going bad which is under the rotor in the distributor.

 

i just had this same problem with a 96. its idling rough now, but it's not as violent as before. changed the cap and rotor with plugs and cables. but fuel preassure, spark test, and spraying brakleen around the manifold is always helpful.

 

Sometimes when you disconnect the battery the computer has to reprogram itself and it takes driving it for a few days to get it back. I think?