I new here, and still navigating...Hey Guys! I have about lost my mind..lol I have a Camaro Z28 1994, I am having Running/ Starting issues after warm up. The Car is Strong and wants to run, and will run, but after up to operating temperature it wants to just shut down, like you turned off a light switch! or may get you to where your going, just to come back to go back home and wont start at all... til after it totally cools down. Takes about an hr.
Thisut is what I have done to the car that I have owned for 5 yrs. I have replaced the OEM opti-spark distributor, with a summit replacement, coil wires and plugs... Upgraded the electrical... New Polished elbow between MAF sensor and Throttle body. New fuel pump (255 series) and filter. and that's about it! Keep up fluids and filter at regular intervals.. like any other car. So basically not much as far as performance mods go... am happy just as a daily driver.
Since this condition has started, here is what I have done. Checked VATS system, voltage checks on opti-spark, Ignition module (but have not replaced) Coil, Checked the only under the hood ground in the engine harness, located right above the starter, replaced the water temp sensor in the WP, Ran an ohms test on OBD1 connector to ECM. Have hooked up a Snap-on Versus Scanner to read DTC's (will not read) not talking to ECM (Blames cable) Have crossed Top two connections with paperclip to possiably read blink codes. (Nothing Blinks) Have hooked up cheaper scanner, Innova 3120 series, and the same. Will not talk to the ECM. So the last step I have done is replace with a freshly reprogrammed ECM and to no avail...same condition!??? I am trying my best to talk to the ECM for some direction... but have failed, yet have ohmed the wires? Question? Can the transmission cause the engine/ECM to shut off I have been by-passing the tranny all along and cant talk to the ECM. HELP PLEASE!!!

 

Fuel + spark = fire. Do you have a timing light? Carry it with you and when the engine kills, hook it up, crank the engine over, and check for spark. One thing that more than one of us has had before is an ignition module that can't take the engine heat, and it kills the ignition. Also when it kills, push in the schrader valve on the fuel rail, with a rag to catch, and see if you get a solid shot of gas. I presume you had this problem before the new fuel pump? If so, I'm leaning more toward ignition.

 

ICM is prone to failure as it gets hot while still working when cool, coil can do the same thing, but not as often as ICM. Voltage check to the input is not going to find these two problems.
This year is OBD1 and you will need an OBD1 scanner to read codes (not one of the $30 boxes that claim to work) The codes cannot be flashed. End of year production may be built with an OBB2 connector, but the PCM is still OBD1, so an adapter cable OBD1 scanner to OBD2 connector is needed.

 

There are very few scanners that work for that car, even if they claim to do so. The Innova 3120 will NOT work despite their claims. See this topic for one designed specifically for your car. And it is free.

https://camaroforums.com/forum/compu...-95-lt1-77363/

If you want, you can check your wiring first for problems. Using an ordinary multimeter set to the 20 vdc range, measure the dc voltage at pin 9 of the DLC (referenced to chassis ground) while the ignition is on and the engine is NOT running. It should measure about 3.5 volts if it is working. This is representative of the "idle" data traffic that occurs on the OBD1 bus between the modules.

 

https://camaroforums.com/forum/lt1-l...ks-94-a-71161/

 

Have replaced ICM and Still a no go? hooked up timing light after fail no spark... but did notice air pump whinning when I cycle the key every now and then (not every time) so pulled fuse, spun motor, re-installed fuse.. and fires right up??? then eventually dies... and can repeat and get the car to fire everytime??? hows that for messed up!!!..lol

 

I do know that the air pump goes to the cat... to heat it up, tell the o2 sensor to run rich to heat the cat, then should shut off... When I bought this car, cat had already been removed...

 

Replaced the ICM, and still the same. have fuel pressure, and no spark with timing light after fail. Air pump seemed to Whine every now and then, when cycling key, trying to start motor. Pulled fuse, spun motor, re-installed fuse, and starts? while at operating temp. did this several times, wait for motor to fail, pull fuse, no start, re-install fuse for air pump, and starts everytime???? I am thinking opti-spark, but its new with only 3k miles on it??? Stupped???

 

wow, yah if it was a cheap opti. does it have a warranty?

 

The Opti, is the best one I could buy, for the early model replacement from Summit Racing. I did check the opti yesterday, I pulled up a how to: and followed all the test. 12v on the outer pins and 3rd pin (pink) was pulsing at the injectors. Tested the coil wiring again, pulsing ground and correct voltage... the way I understand it is? The opti sends a signal to the ECM to tell the coil to fire while also sending a pulsing single to the injectors to send fuel? or does the ECM send the injector single as well? I want to say the module in the opti is going bad when at operating temp, but I preformed these tests after up to operating temp, and engine fail...??? Also looking at the MAP Sensor... its probally original, and I'm thinking it may be clogged or dirty. Will this cause the ECM to shut down the motor? I have cleaned the MAF sensor but did not know if you can do the same to the MAP, as it is a sealed unit? Still guessing... Today am going by Autozone to see if I can get their scanner, and see if that works.... Man I greatly appreciate the advice and the help! Am still looking for some kind of direction to go in....