Okay guys, i really need someone to be my hero today.
I have a 1995 z28 camaro with a stock lt1. In 2012 i stopped driving it due to massive oil leak from the cam seal behind the waterpump. I replaced all the timing cover seals and such aswell as the optispark which was oil soaked and running like crap with a cheaper off the shelf unit. (wai distributor i believe)

I also changed the spark plugs (acdelco) and spark plug wires (prestolite). At that time my priorities went elsewhere and the car sat for three years on the driveway in that state with no cooling system attached. Until about a month ago one of the other cars pooped out and we had to bring the camaro back to life.

I put a new gates water pump on it and a new deka battery and threw it back together with the old radiator and such and it started right up and ran great to my suprise. I went and smogged it and it passed flying colors, even had good power.

Driving it for a week or so i noticed it would die very seldomly. The harness to the opti was very old and brittle from the oil abuse, the clip that holds it to the opti was also broken off so the harness would vibrate loose and kill the car. after that it would only crank and not start. I would just use something long and skinny to push the harness back in and it would fire right back up no problem.

Eventually it got worse to the point it wouldnt stay running or hardly even start. So i got the new harness and put it in, which was a pain in the *** because one pin was bent on the opti connector so i had to take everything back off including the opti to straighten the pin and secure the new harness so it sat flush.

Got everything back together and it wouldnt start. It would just crank and sputter and blow a few clouds of smoke out the intake. It seemed to me like it was out of timing, like the plugs were firing on the intake stroke. so i fugured i installed the opti wrong. well back apart everything goes yet again. I re-installed the opti, taking my time to make 100% sure the keyway was aligned with the pin.

I tested it before installing the waterpump back over it and it fired up so i turned it off and proceeded to put it back together. Once everything was on and hooked up i tried to crank it and it would do the same sputter thing and a few small backfires. I kept trying until the battery died shortly after. Once i put on my jumper box and tried again it fired up. I let it run for over an hour and charge the battery. i didnt try revving it at that time because i was waiting for my new intake elbow to arrive and i didnt want it to stall and not start again.

Today i got the new elbow and installed that and made sure everything was hooked up and all wires were zip tied away from moving parts.

Of course the thing wouldn't fire up at all! Same situation, cranking and occasional small combustion with a cloud coming from the intake. After trying a few times i did this test located here http://www.ls1lt1.com/forum/lt1-%7C-...optispark.html everything seemed to check out, only test i didnt do was measure resistance across the coil. Finally after multiple tries i was able to get it to fire and it sounded great. But when i would give it any kind of moderate load it would stall out.

If i slowly give it throttle it will rev up but if i hit the throttle in any sharp matter it chokes out and dies. Then it wont start again for numerous tries. I really dont know where to go from here.

My only guess is the optical on the optispark is garbage and isnt sending spark at the time the cylinder needs it. Also the stalling could happen when the opti needs a sudden timing advance. Or the pcm is bad which is prolly unlikely. i don't know. i know im getting good fuel pressure and i can smell the engine flood up after multiple failed tries at starting. I also get the same results using starting fluid in the intake manifold. hopefully the pros can help me out?

Here is a cellphone video i took to kind of show where i'm at now

any and all help is greatly appreciated!

 

Im also going to blame the opti again, the no name cheapo chinese ones fail way too often. When you pulled it apart, did you take the opti apart and loctite everything inside?

I would also verify your spark plug wire routing, making sure nothing is burned and they are on the correct cylinders.

 

How many miles on it? Optis don't live forever...I'm not saying it's your optispark.....however mine had the exact same symptoms with the puffs of smoke coming from the intake from sporadic combustion when a cheap parts store optispark took a dump in my car.

 

thanks for the reply guys. this was def probably the cheapest opti i could find. i didnt loctite anything, just threw it on. it initially ran fone so i thought nothing of it. being i bent the pin installing the new harness, maybe i did some inrernal damage to the unit?

 

My car did the exact same thing when the fuel pump was clogged with bad gas after sitting for ~3 years.

Would struggle to start, idle OK, then stall as soon as you blip the gas. Gently giving gas it would rev though.

In my case, the white aftermarket fuel sock completely rotted away and plugged up the basket screen. Replaced it with the green plastic OEM fuel sock, drained and cleaned tank, then reinstalled and now it revs fine.

 

Sounds like it could be a combination of bad opti and old gas. In the video it seems like its a fuel issue the way it only turns off when you rev it.

 

interesting. it sounds very probable, but wouldnt the starting fluid in the intake manifold make a difference then. if i spray it with starting fluid it has the same effect as when i let the pump prime

 

what would be a surefire way to pinpoint that? fuel pressure test?

 

Ignition problems usually rear up when the motor is under load...like high gear+low rpm or hard acceleration. If it idles OK but does it during a free rev with no load, I would think fuel first.

 

If you've ever changed the fuel pump I would check with a light through the trap door.

 

update: tested the fuel pressure and spark today. i can verify the icm is working correctly, as my spark tester was consistent, even under no-start conditions. the fuel pressure is about 42psi at prime, and a hair under 40psi while running remains consistent when i slowly rev it. but still stalls with a sharp rev. however pressure does not drop off so im ruling out fuel as the issue. can anyone verify if the spark looks strong enough. seems kind of weak to me, but i dont know. any ideas where to look next?

heres a video of the spark and fuel test:

 

Have you scanned it for SES codes? If not, be sure you do...some codes don't set the SES light.

I'm surprised at how fast it shuts off.....like a switch. Have you tested the TPS sensor?

Edit:
I just watched the end of it.....I think you may need to do some Opti diagnosis.

 

That video still points to fuel IMO.

When you rev it the fuel pressure should be increasing, not staying the same. It looks like FP actually goes DOWN when you rev it. At :10 secs it shows as 36psi idle, then 34psi @ :21 with higher RPM. That should never happen unless the pump is weak/clogged since the pressure reg is vacuum referenced. Pressure doesn't mean volume, so a quick burst of air inside the intake when it cant add enough fuel fast enough will stall it.

FWIW mine would hold pressure fine when giving it gas slowly as well just like in your video, but would still stall when I blip the gas. Do you have the trap door to pull the pump assembly?

 

it should have the trap door. ill try to get eyes on the pump today and make sure it isnt caked with varnish. if you do sharp revs the fuel pressure goes up right before it stalls out.

 

With that test video it was difficult to see what the FP tester was doing since you were all over the place. at :31 seconds in you try a quick rev and it does appear fuel pressure instantly jumps up into the ~45psi range. I am leaning more on the weak ignition side than fuel. I think the ignition cannot handle the higher demand for fuel and kills the motor. JMHO.

 

what is the TPS volts reading during the test

 

Did not notice that, I thought it was just going down when revving.

Still worth a look, but its probably fine if its going to 45 when revved.

 

update!! i was able to get a warranty on my opti and put that towards a new delphi unit. i changed it out over this weekend and lets just say im very satisfied. it starts every time, runs a whole lot better and better yet, no stalling!! i wanna thank you all for the help in figuring this out, ive definately leaned why the oem unit is 200$ more then the chinese counterpart lol. just looking at the un its in comparison you can clearly see how much heftier and higher qualithy the delphi part is. thanks again for the help guys!

 

Right on, glad that fixed it.

 

Damn opti