Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Check for vacuum leaks, spray carb or brake cleaner along the intake manifold and all the vacuum likes. If you have a change in idle this indicates a leak. . Check the idle air control, I would actually remove the throttle body and the iac clean them throughly. . Try adding fuel while it is running, starting fluid will work to see if it smooths out indicating a fueling issue. Check the ohms of resistance on the injectors, they should be 11.8-12.6 at room temperature. I would also check the exhaust system for a blockage in the exhaust system. You can remove front O2 sensor to see if this helps the running condition. These are known to have the problem and it will burn out the injectors making it not even start if it is the catalytic converter. If all of that checks out the problem is likely to be the PCM powertrain control module.
You replaced the catalytic converter and the fuel injectors?
I am very confused you stated you have done that already. I am pressure sure that you have an issue with the catalytic converter it is extremely common on these. You are wasting your time trying everything else first before tackling the most common problem. The ignition module will cut spark not just make it run rough. You need to begin with the catalytic converter. If that does not solve the problem replace the pcm for being bad.