A few weeks ago i purchased a 1996 Z28 6 speed with approx 177k miles.

The car would run and drive but would eventually stall and wouldn't want to restart until after sitting for a while. initially i thought of ICM (mod had not been done and looked to be original). once i got the car home i found a resolution code which lead me to the optispark as well.

with only having $500 invested into the purchase of the vehicle i decided to purchase new plugs, wires, coil, ICM and optispark.

before starting to work on the vehicle i tried driving it just to get a feel for any other issues that may arise (brakes suspension etc). It would run fine through first gear with plenty of power then would bog completely when getting on it hard in 2nd. it eventually stalled out and i was able to restart and get it back home. after sitting in the garage the vehicle would crank but would not start.

at this point i decided to tear it apart. i started with replaced pads and rotors all the way around. further inspection under the hood showed some very rigged wiring for the electric fans corresponding with 2 DTC's. i pulled the fans, cut the pigtail/connector nearest the fans and removed the wiring (will install my own relay, wiring switch etc). I then found the AC compressor to be gone with a dummy pulley installed in it's place.

i decided to remove the AC Condenser, lines etc just to free up some space. most of the vacuum lines under the hood were broken so i decided to remove which ever unnecessary emission systems to de-clutter the engine compartment. i removed the AIR pump and corresponding vacuum lines and plugged up the loose ends. i installed M18 drain plugs in the exhaust manifolds to plug the old holes.

Then proceeded to remove the intake, throttlebody water pump, serpentine belt, harmonic balancer, coil ICM etc etc. i replaced the spark plugs (gapped to .045) routed the plug wires, sanded and cleaned the mounting bracket for the coil/ICM and remounted with washers to space it away from the cylinder head.

At this point i realized the optispark i ordered through autozone (terrible choice i know) only contained a cap and rotor. when i opened up the optispark on the vehicle i found a lot of carbon build up on the rotor which i thought may have been the culprit. i put the optispark back together with the new cap/rotor.

I made sure to line up the dowel correctly with it's mounting point.I replaced all throttlebody gaskets as the upper gasket appeared to be a possible problem (looked wavy). i then went through the process of putting the vehicle entirely back together. When i finally tried to start the vehicle. it would fire up and stall if i didn't have my foot on the gas pedal, if i revved the vehicle up the engine seemed to run fine until returning back to idle. The exhaust would smell extremely rich.

i cleared codes and the code for low resolution pulse came back. I Knew i should have replaced the optispark as an assembly so i ordered a new one from summitracing.

i went through the process of tearing everything apart again and replaced the entire opti with my brand new one from summit. i put it all back together and now the vehicle will crank and sound like it wants to start (stumbles) but will not fire up. can still smell a little bit of fuel like smell but not nearly as bad as previously.

the opti harness is new, i've tried unplugging the MAF to pull it from closed loop to see if it would start and the condition does not change. There is no DTC's. i tested fuel pressure and with cycling the key twice would sit at 45 psi during cranking it would seem to drop however at lowest to nearly 25 psi. There is a nice blue spark from both the coil and the plug wire.from the opti when cranking. The VATS light goes out as normal.

I tried using starting fluid in the intake to see if it would start but it backfired through the intake and blew off a vacuum plug from the throttlebody. what am i missing here? is it possible the optical sensor and wheel could be timed incorrectly out of the box? I'm at a loss and am really sick of making the concern worse with every repair. any help would be much appreciated...

 

 

I knew it was very crucial to have it aligned properly and made sure to line up both the hole and the dowel, I was very confident it was a correct fit, 2 of 3 mounting points were flush with no effort and the top left was maybe 1/10" gap. however at this point i'm likely going to tear it back down just to make sure because it acts just like it is off time. it seems like when it is coughing and stumbling upon cranking it will sometimes backfire sounding like it is coming through the intake. the car has been slow cranking as well, I thought maybe was due to an old battery so I pulled my red optima out of my daily and installed that and the car seems to still be slow cranking. I have to put a battery charger set to 300amp and a jump pack on it just for it to crank over as fast as it used too. fuel pressure seems to be maintaining near 30 psi while cranking. I used the jump harness by the PCM and verified fuel pump would prime, although today I was unable to get the fuel pressure gauge to go above 37-38 even with multiple key turns. this car is leading me in every direction.

 

Check that you got the plug wires all in the right spots on the opti, too. Do a test fire of the engine before you put the water pump back on (perfectly ok to run for a short period).

And by all means, please use some paragraphs in your posts.

 

My apologies,

plug wires have been checked, opti harness is fully connected.

next time I will definitely try that before committing to installing the pump.

I'm going to tear it down again and try installing the old opti and see if it will fire up like it previously did.

i'm getting fairly fast at doing this I might add.

 

Brother I know the feeling, lol!