jwade88

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 maro 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 Diagnose The Optispark - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums 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!

Injuneer

Not pretending to be a "god".... just trying to help.

Basic first steps:

Have you scanned if for codes?

Have you checked the fuel pressure?

Have you considered scanning it with data logging software, like Scan9495:

https://www.camaroz28.com/forums/com...95-lt1-874306/

I'm sure you are aware that a cheap Opti will generally give poor results. Did you loc-tite the rotor screws before installing?

jwade88

i have not done any of that. i kno fuel is getting where it needs to be. the rail has a lot of pressure. havent gauged it though. as stated before. even starting fluid has zero effect on it which leads me to think its ignotion related. fuel filter was also changed 3 weeks ago before smog. my code reader is only obd2 compliant, it attatches but fails to link with the 16pin dlc. is there any way to maually pull codes without buying an obd1 scanner?

Injuneer

95 is a problem pulling codes, with the 16-pin OBD-2 ALDL connector on an OBD-1 PCM. Hence, OBD-2 scanner will not work, and some supposedly compatible OBD-1/OBD-2 scanners will not pull correct codes, due to faults in the scanner code database. If you can find an old Auto Xray OBD-1 scanner, or any other with a 12-pin connector, Shoebox has the solution:

http://shbox.com/1/xraycable.jpg

1993 was the last year you could flash the codes on the SES light by shorting the pins in the ALDL connector.

Scan9495 is the best tool around.

You will have pressure in the rail... but how much? May be enough to start it, but may drop off when the engine starts to run, and fuel demand increases.

If the optical cam position sensor in the Opti fails, it can set code DTC 16, which does not turn on the SES light. But that code will shut down the fuel system. I'm not familiar with the test procedure you linked from LS1LT1.... but Shoebox has the one we use (which may be the same):

4th Gen LT1 F-body Tech Articles

Similarly, failure of the IC module will set DTC 41 or DTC 42, neither turns on the SES light, and both shut down the injectors. Have you had the ICM tested?

jwade88

im for sure getting the low voltage reference from the pcm to the icm (terminal B) and terminal A and D have battery voltage from the coil. C seems to just be a ground. is there any other way to test the icm?

Injuneer

Take the ICM to an auto parts store to be tested. So far all you have tested is the signal going to the ICM and the power supply. Make sure the shop tests it several times in a row to test for failure due to heat soak.

jwade88

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:

Thirim

I don't see the MAF, is it disconnected or connected and off to the side? .. I also don't see the IAT sensor. The MAF shouldn't be a deal breaker as long as it's unplugged. ECM will revert to speed density, not the best idea but I don't think it would cause your problem. The IAT sensor would make it hard to start though. Throw your elbow back on with the 2 sensors connected just for fun.
..PS - Not a god.. lol

Injuneer

Exactly... if the MAF is still connected, it's going to stumble when you move the throttle. With the MAF disconnected, speed-density needs a good IAT signal and a good MAP signal.

Revving the engine in the driveway doesn't put the fuel system under any strain. It has to be tested while driving, with an appreciable load on the engine. Can't tell from the limited view of the gauge if it's responding to the throttle opening. Should peak closer to 43psi when you blip the throttle. Check the vacuum compensation line for the fuel pressure regulator. At idle, with the vacuum line off, should be 43.5psi. GM specs accept anything from 41-47psi. When you reattach the vacuum line to the FPR, pressure should drop by about 8psi, or maybe 33psi, Slowly moving the throttle should only cause minor movement of pressure, as you indicate. Rapidly opening the throttle should be as described above.

By not scanning it, your basically fighting with one hand tied behind your back.

maybe2fast

the bent pin is where I am stuck at. I bet the pin when bending it back damaged the sensor. replace opti again...sorry man

or in all the dis-assembly on and off you soaked it in coolant.

jwade88

i get that feeling too. the pin that bent was for then low res output too.. im going to try to see if i can atleast warranty the opti today. if anything i can eliminate that as the problem if it doesnt fix. def going to get an oem replacement.

jwade88

im still trying to get hands on a 12pin obd1 scanner aswell so i can perform tests like injuneer stated. im curious too see what codes are stored.

maybe2fast

freescan9495 is awesome. just need to order a cable...and that cable can be used to tune the car also.

KYWes

Actually it's just Scan 94/95 and it is an excellent program.

Freescan is good too!

Both are free. Scan 94/95 is available on CamaroZ28 forum

Computer Diagnostics and Tuning - CamaroZ28.Com Message Board

jwade88

so i was able to warranty the opti and i put that towards a new delphi unit. everything is 100% better. starts every time, no stalling, all power. thanks for the help in getting this figured out. shows some things you cant cheap out on, whether the unit was junk or if it was me ****ing up the connector. regardless, it works now and im happy. thanks again.