What make my car backfire while trying to start it up?

Sounds like it may be out of timing,weak power and backfire is sign of advance timing,meaning flooding it self,bogging out,check the timing.

Check ur wire mite be cross

Thanks this helps a lot will this allow the 4 barrel to open up as well?

Or one of ur wire mite have a split n it. Or ssitting on the manifold..

Also check fuel filter and clean carb with carburetor cleaner.

If the problem started all of a sudden its quite likely that your timing chain is loose and has skipped a tooth. The only fix for that is a new chain and gears in the front of the engine. Takes the better part of a day if you're a do it yourselfer. You'll need to rent a harmonic balancer puller, but otherwise hand tools will do the job.