95Z Cranks kind of fires, let off the key and it stumbles
 

Ok, I hope I have peaked the interest of someone who has had this problem or know something about it.

Scenario:
Driving to work, shut off car, come out 8hrs later and it won't start. Just cranks, and when you let off the key it kind of backfire/runs like it's spinning in rotation backwards. Just a couple times thought and you can smell the faint smell of exhaust in the intake.

From what I know there are no codes as of right now ( I can't read it I have the OBD1 square connector and not the OBD2 connector on a OBD1 car.

Car still does the original problem after all replacements..

Replaced;
Opti - 114K on the original
Waterpump - Seephole leak
TPS
Spark Plugs
Fuel pump - dying when you crank it would frop down to 20psi new one stays at 44psi.
Timing Chain and oil pan gasket - no relavence other then to show what a frustrating two weeks it's been.... Oil pan gasket had been split by a previous mechanic.

Whats old yet....
O2's
IAC motor
Spark plug wires
Coil, Module

I took the ECM off my 94 along with my Opti connector (converted 95 opti spark on mine), coil and module, with no satisfing end result :(.

Help is greatly appreciated,
Tony

Re: 95Z Cranks kind of fires, let off the key and it stumbles
 

Could be a coil, you do have a non OBDII car so I don't think it throws a code.

**** I know this happenened to me once, I can't remember what it was though.

Sorry, I'll let you know if I remember.

Re: 95Z Cranks kind of fires, let off the key and it stumbles
 

Coil and module off mine were put on his and it didnt' change the problem, wish it did...
My garage is full of cars that don't run :( I think my garage jinx's cars that enter, never to come out... 2 wide 2 deep and all 4 spots are filled with non running car...

Re: 95Z Cranks kind of fires, let off the key and it stumbles
 

So let me get this straight, you used the original opti-spark back half and installed new cap and rotor assembly? If so, im going to say your opti itself took a crap. That just happened to me, and sometimes it would start and rnu til it got warm, then start missing and losing cylinders, and stalling out in the end. Just b4 it would die it would throw a code 36, which is the PCM losing the signal from the high resolution side of the optical eye, or seeing an extra signal from the low resolution side of the optical eye, neither of which are good and one will kill the engine all together, the other will make it run choppy as I believe it has less spark accuracy when that happens. If you replaced the whole opti as a unit and still have the same problem, sounds like your PCM itself is going bad or you have a wiring issue with the signal returns from the opti to the PCM, check your opti plug and the wiring from the opti-plug to the connector on the manifold stud on the passenger side (4wire). Check for corrosion or damaged wires. If none of this helps, ask slopok, he put me in the right direction when this happened to me.

Re: 95Z Cranks kind of fires, let off the key and it stumbles
 

Opti is Brand new complete GM from Sam Taylor I had it sitting around for my car and decided to let him use it.
And when I used my ECM I put everything back on my 94 and it starts fine.

Re: 95Z Cranks kind of fires, let off the key and it stumbles
 

The Car Tony Is Talking About Is Mine. I Was Driving It To Work It Started Backfiring. Got To Work And Parked It. Hasn't Started Since. If Anybody Out There Has Seen This Problem Please Get Back To Us.

Thank You,
Josh