I have a 1985 IROC that I stupidly ran with no mass air flow sensor for about 3 months.
right before it decided to die on me and not start at all it started pinging and back fireing.
that same day I bought the sensor put it in and noticed it would still ping and backfire if I kicked it down even just a little. I parked left it sit for the night and the next day it would not start at all.
I could spell strong un-burned gas but it would just crank away.
al checked for spark and i had it . c
an any one help

 

I'd pull a plug or two and see if they look normal. Could be a lot of things, but probably a load of carbon deposits in the chambers. Try holding the gas all the way down and listening for any fire. If you have fouled plugs and/or weak spark, this should lean out the mix a bit and make it easier to start.