Re: 1998 4.3Gi hard to start cold and rough idle....HELP
I wanted to add my update to this thread, for future readers. Hopefully 1952m38 and myself can save you some money and time.
I have the same engine, 4.3gi, same vintage, same exact problem as the OP. At first, I tuned the engine up fully (wires, plugs, cap/rotor, fuel filter). No change. Hard cold starting actually seemed to get worse.
Change the IAC valve & the engine coolant sensor. Hey, the parts were 15 years old and I sleep better at night knowing they are new anyways. Made the hard starting decrease slightly.
Tested my low pressure fuel pump. Inop. Replaced pump. Now the boat will crank for 10 seconds, nothing. Try again, sputter and stall out. Try again, it might start or it might sputter and stall out again. But usually by then it will fire. Before I replaced the fuel pump it would just crank and crank and crank for 5 minutes (in 10 second sessions) and no fire. So thats progress at least...
Heres what me and the OP have come to the rough conclusion of: The hard starting is only when cold. We've got fuel. Theory: Coil or ignition module not firing when cold, thus at first the engine floods with fuel, hence the "sputter and stall" behavior. The spark is either non existent at first or too weak to fire the rich, cold start mixture. When the engine is warm, it starts RIGHT up. Like fires less than a second after turning the key. Lean warm mixture = easy to ignite. Cold rich mixture = ehhh, not so easy.
1952m38 is going to replace his coil or his ignition module this weekend and post his results. Again, posting this to future readers with the same issue.
