I have 91 Firebird with LT1 out 94 Z28. I rebuilt it 2003 went ahead did 95 style cam so I could use vented opti. and it has ran great since then. Now it wont start injectors 1,5,2,6 wont pulse 3,7,4,8 will pulse with noid light when engine is cranking. I though right off from the get go got to be opti problem so I got another new one from elitesparkplugs put it in same senario Would bad PCM do this or sensor acting up make it pulse like that? ICM maybe ? IM lost any help or ideas would be great.

 

Are you sure you counted the injectors numbers correctly? With half of them firing, I would first suspect a blown injector fuse, but your numbers don't coincide with what injectors each fuse powers. Each fuse powers every other injector in the firing order.

 

No I'm wrong on this not enough sleep sorry for confusion the only injectors that I can get a pulse from are 3,8 the rest are dead. Which was same senario before I changed the old opti out for the new one. I checked all pink wires on every injector they all have good 12 volts the injector return ground wires test good from the injector back to the PCM. Checked sensors voltages seem fine. Did ICM test see PCM triggering which it did. Check voltages at opti harness everthing good from PCM. Unplugged MAF sensor still no luck. Ran around car three times (just kidding) still no start. I was looking at my spark plugs this morning after changing them looked like 3,7,4,8, were firing some 1,5,2,6 were not. Sorry I got this all mixed up with my injector problem. I went ahead spark tested all sparkplugs they are sparking good. Just need to get some fuel dropped in. Maybe best thing send PCM off have someone check it rule out the problem. The search will continue!