View Full Version : LT-1 Hard Start Issues Solved

08-02-2012, 07:01 PM
Recently had my 98' 190 out of the water to do a few minor projects. The idle has always been a little bouncy when it first starts. To try and alleviate some of this I cleaned the IAC and the port it fits into. I also changed the fuel filters at the same time.

When I relaunched the boat wouldn't start unless I cracked the throttle. Once it started it ran perfect, idled perfect, etc. Every start was needing the throttle cracked open to catch. If I didn't crack the throttle it would start and die immediately. I thought that maybe I'd messed up the IAC and might need a new one.

After reading on here (especially everything I could find that the Jim's had written on diagnostics and how the EFI functions) I checked first for stored codes and got nothing. Then I pulled the IAC and tested it between my fingers turning the key on and it moved like it should.

Doing more reading I stumbled on a forum for Pontiac Firebird owners with the LT-1, which I think was a mid-nineties engine option. There I found the following procedure to reset the IAC:

Depress accelerator slightly
Start engine, then release accelerator pedal, run engine for 5 seconds
Turn ignition "OFF" for ten seconds
Restart engine and check for proper idle operation

Either this procedure is the same for the EFI in the marine LT-1 or my ECM finally relearned how to hold an idle with a clean IAC, but after doing this the boat starts as soon as I hit the key, every time. Hopefully this can save someone else a headache and a trip to the parts store.

08-02-2012, 09:11 PM
What's the IAC?

08-03-2012, 01:25 PM
Idle Air Controller. Its a little worm-drive motor that moves a pin in and out in a passageway in the intake to control the idle speed when the throttle plate is closed.