I need a diagram of the engine for a 1998 chevy cavalier

Don't have this but if you could have given more info maybe I could have given you some elimination clues.
Note that the computers (ECM)  on these vehicles are in front of the wheel well behind the passenger head-light (access from underneath or take inner wheel-well apart and get at the ECM and check that it hasn't gotten loose from body.  This allows the wires to fray and rub against the body and cuts off a lot of the systems.  This would be a good place to start.
Also note that the injector seals have been problems on these cars for years, assuming it's a 2.2 and is easier to replace complete intake but is a $10.00 fix to get new seals - just a bit tricky to put them in without damaging a seal - which will severely flood a cylinder and cause a lot of smoke from the exhaust - very gassy smell and smoking bad.
I suspect that the ECM wiring is your problem.  You may want to get a piece of harness from the scrap-yard and move this to the top of engine where it is on the newer models.
Good luck, hope this helps.