Have an '89 which also had similar problems, actually two similar problems. One was that when hot (and occasionally cold) and the engine was shut off, it would not restart for half an hour or so. Turned out to be a bad ignition module.

The second was when hot and idling, or even when starting cold, it would run rough and stumble. Opening up the throttle whould smooth it out. I ended up changing the injectors and it solved the problem. Looked like a couple were not holding pressure and likely dumping fuel at an excessive rate at idle.