If it's getting GOOD spark - HOT white/blue looking- and it's getting full shot of fuel then it's not getting enuff air OR not getting all 3 at the right time. Try checking timing marks on cam belt; it may have jumped a a few teeth if it was worn especially if it's the original belt. Also , on battery ground cable there is a dedicated ground for fuel pump that looks like an inline fuse holder- had mine work loose and made intermittent contact. This is presuming you have checked the oil for contamination of gas via a bad fuel pressure regulator; the oil level will be high and smell like gas. Check pressure on fuel bleed valve; connections on manifold air pressure sensor. Actron makes a code reader for $29 at Oreilly's. My 87 did a similar thing and it was bundle of vacuum lines had dropped onto exhaust manifold and melted thru along with the distributor spout connector wire. Good luck , man! It's almost always something simple.