93 4x4 5.2l , after replacing flex plate, the engine starts but is sucking way too much air just idling and will not rev up. The air is sucking through the IAC motor(brand new, used one same thing) on full open while idling. On level ground I can put it in gear and crawl a little before it dies, but it is back firing terribly every time I give it gas.

Any Thoughts?

 

Sounds like a timing/ignition issue. Check to make sure the wires to the crank sensor didn't get pinched. Make sure the distributor is in the correct location. Make sure all plug wire are in the correct locations. Are you getting any check engine light codes?

 

No codes. Will be looking closely at the cps tomorrow, all wires in place and good spark.