Not sure why I can't get my 3.1 to run. (Need some outside Ideas)

[KCarter1982]

I have a 92 z24 3.1. Bought it a month ago off of Craigslist.

Problem I am having is weird, haven't really seen a car do this before. It has both spark and fuel. When you try to start it, it will crank, and then backfire real loud out of the exhaust. I am just wondering if anyone has experienced this with their 3.1.

It's weird the way it does it, it will crank just fine and then the starter seems to stop, or bogs down (hard to explain) then it will start cranking again just fine and then BOOOM. It sometimes acts like it wants to start.

I've had a few of these J-bodys with the same motor in it and I've never had one do anything like this. I just put this motor in this car, it had a bad one in it before (Head gasket AND a crack in the Head), but even it did the same thing. (375 for reconditioned heads, or 350 for a motor with 75k on it.) I didn't reuse any sensors or fuel injectors off the old one since the motor I got was in "running condition".

I bought this car in this condition, it did the same thing with the leaking motor, so I am at a loss. And starting to wonder if it's not the ECU. What are some symptoms of a bad ECU? Can it cause injector pulses at incorrect time? Or spark at incorrect times? Crank shaft position sensor? Or am I totally wrong thinking it's the ECU? I've taken it out and inspected it, everything looks in tip-top shape, circuit board and all looks brand new.

But that's what I got, need some new ideas from different people.

Any new ideas is greatly appreciated. Just some outside thoughts cause I am running in circles with mine lol.

Thanks

[andy_99w_csh]

check your timing, cam and crank sensor

[inafogg]

yes i agree!!!1st thing i thought.... out of time.

[J-Ri]

Just about has to be the PCM. If two engines do the exact same thing it is very unlikely to be anything else, everything else has been swapped with a different used one.