Categories
- All Categories
- 15 Non-Rinker Boats
- 2.9K General Boating Discussions
- 294 Rinker Custom Projects
- 136 Trailer & Trailering Discussions
- 473 Generator Discussions
- 172 Rinker Photo Gallery
- 364 Rinker Sport Boat Forum
- 3.9K Rinker Express Cruisers Forum
- 1.2K Engine Discussions
- 1.2K Electrical Discussions
- 662 Rinker Support Q&A
- 595 Rinker Marketplace & Classifieds
- 67 Rinker News & Updates
- 102 RBO Forum Archives
- 175 Region-Specific Questions
- 31 Canada
- 136 United States
Comments
this is a poor image to use for this comment, but it's the best I could find... even though it's throttle body fuel injection depicted, the principle remains...
watching just the plunger on the IAC, notice how 'warm engine idle' is more closed? the engine has a better grip on trim and conditions when the engine is warmer (even after sitting for a while, everything is still primed and the IAC map is still set for a warm/running engine)... it doesn't need as much air.
this is the reason I commented earlier about turning the key and waiting a second or two... the PCM should take a couple sniffs of sensors and realize what is going on- and if you listen real close while right next to the engine you'll hear the short burst hum of the valve/plunger moving.... that is why turning the key to run but not starting for just a few seconds can mean all the difference.... again, it's because the plunger is in the same position it was in when the engine was last running... it needs to be more open for that BOOM!! (fire right up)....
now, at the same time, IF- if that passage the plunger manages is even slightly clogged with gunk, you can imagine the engine would be REALLY starved for air, and necessitate manipulation of the throttle plates to compensate... that is really all you're doing when you open the throttle while the engine is cranking- that and dumping fuel you likely don't need that will be expelled through the exhaust in that infamous boat engine rich smell....
that little valve is pretty important, no? a cold engine KNOWS it's cold, as the coolant temperature sensor next to the thermostat is a sensor that reports during the built in test (BIT) in the first half second juice hits the PCM... that, along with CPS, CKPS, and TPS... the IAC change of position is a movement dictated by those... if all the other sensors suggest to the PCM that the engine is already warm or even somewhat warm, the IAC is left partially closed, which creates the hard start (but starter turning fast) condition... the hard start (starter struggling) is also often a condition created by downwind of this same situation- when all sensors check out and the PCM feels it can advance timing a bit (advanced engines are harder to turn, as they create that magic burn, which may be only a partial burn, creating high pressures in the combustion chamber/cylinder tops than an engine that doesn't touch of the burn until the piston is closer to the top)... the reason why it happens is the PCM is applying the same logic it was applying when the engine was turned off... it hasn't flushed the short term logic... which is why turning the key on and waiting a few seconds makes a world of difference...
make sense?
06 Rinker 270