Re: 1989 GM 3.0 OMC rough idle then dies - HELP!!!!
Interesting coincidence! My '86 is doing the exact same thing.
Just spent a couple hours out in the driveway trying to figure it out.
On mine, the problem has been hard to diagnose, since the engine needs to run for a while before the trouble occurs. We put it in the lake on Sunday and started right up. First time out this season. No sign of a problem until high speed run across the lake to our favorite spot. as I throttle down to idle the engine died, but we just threw out the anchor and fished a couple of hours.
When it was time to go home ,the throttle had to be opened about halfway to get the boat running,(thought it might be flooded from percolation) and it died going into gear. Restarted, got into gear, and headed back to the dock without any noticeable trouble, until attempting to idle.
I wanted to let the engine idle a little before approaching the dock and see if it was stable, in case I needed to pop it into reverse. Engine died.
I disconnected the connector for the ESA switches to eliminate a possible input, and it had no effect.
Once the engine died, I could barely get it started, and it wouldn't run well at any speed. After 10 minutes of monkey business, we got the boat to the dock. Smelled raw fuel (from the exhaust). No sign of flooding or fumes in the bilge. I'm thinking that it's definitely an intermittent ignition problem, and I'm betting on the ESA module at this time. When I fired it up on the muffs this evening, it ran perfectly at first. Ran at fast idle for about 5 minutes (making sure I had plenty of cooling water flow). When I returned to idle, it started missing progressively worse over the next few minutes and then died.
I installed new points and condenser, dwell set to 30 degrees, timing set to 4 Degrees BTDC, idle speed 800 RPM. Running great. adjust idle mixture screws-running smooth. I raised up the idle for about 5 minutes and throttled back down- still running good. Engine temp normal, ignition coil cool to the touch, etc. Suddenly, the misfiring started up again. I hooked my timing light up to the coil wire, so I could watch it pulse on every firing, and it doesn't light while the engine misses, and/or dies. I am going to check my wiring diagram, and run a test tomorrow by disconnecting the ESA module from the coil, as I believe that it must short out internally. I'll post the results. I'm not putting it back in the water until I'm satisfied that I have found the cause.
