idle RPM and IAC counts are not responding

**jim_in_dorris** · 03-30-2014

Too much airflow past the throttle blades, screw the stop in and watch the idle.

**EagleMark** · 03-30-2014

How many IAC counts when this is happening?

Yes, Desired Idle in $42 is CL and fully warmed up. Most boats run a low thermastat and never reach what a stock bin thinks is warmed up.

EDIT: Data log shows 160*f, it's not warmed up. IAC counts are in 80's and keeping idle high because it's cold. I'll look at your bin in the AM and see if I can make the changes needed to be warmed up at 160*f and lower your IAC count for cold...

**mmigacz** · 03-31-2014

Any idea's?

**EagleMark** · 03-31-2014

Yeah lot's of ideas and then I saw your cam specs and this is in a boat, no O2 so how do you tune it? Fuel VE1 table has some major issues...

Even if you got the idle down to 850, in a boat that is not going to be low enough RPM to get into gear... BANG! Even if you have a blip switch. Then take off and be to fast for no wake or docking.

Anyway here's your bin back with a couple changes to get IAC counts lower, but I'm not sure with a 160*f thermastat and no O2 sensor OL does not respond to desired CL idle as well as CL.

**steveo** · 04-01-2014

many marine boxes of the single lever variety also advance throttle slightly when in gear all on their own, or the linkage can be adjusted to do so.

he's also a shaft drive probably with a pretty soft transmission engagement, so engagement at low idle might not even be a problem.

with a boat i might just ditch the IAC anyway and just use the blades. it's not like you need any of the fancer IAC stuff like throttle-speed follower, and you spend very little time at idle in a boat, so a bit higher of an idle wont hurt anything. people are generally used to cold-starting a boat with advanced throttle anyway, which im sure would work fine.

obviously this thing is dry exhaust above water? fresh water use only?

no real reason you cant use an o2 sensor, but shouldn't really be necessary. boats are pretty easy to tune, you dont have a lot of load variation, it's only going to use a very small portion of the VE and timing tables. there's pretty much a 'getting on plane' and an 'already on plane' zone in those maps, and you'll almost never be outside of them except in weird situations like dropping the throttle hard from plane, or trying to climb a giant wave with a boat full o' people.

**EagleMark** · 04-01-2014

Boat tunes spark advance and VE tables sure don't resemble car tunes!

**steveo** · 04-01-2014

welcome to my world.. boats are what i do.. always throws me for a loop. at least inboards are car-like.

you want to see weird FI, look at some of the outboard crap i deal with...

"65kpa at idle and 60 kpa at wide open throttle, but 20kpa while cranking!? what the hell..."

"20 degrees of idle spark...... ATDC!? on a four stroke!? that cant be right.. well i'll be damned."

"one exhaust cam is advanced 10 degrees, the other one is retarded 8 degrees, but the sensor says they're both retarded 15 degrees? if i fix it, it doesnt start?? must be by design..."

**Fast355** · 04-01-2014

Originally Posted by EagleMark

Boat tunes spark advance and VE tables sure don't resemble car tunes!

Which I find weird in itself. I remember one of the GMEFI list guys doing a TBI conversion on a 4.3 in a boat. Claimed he used the stock 4.3 Astro van fuel/spark maps on the boat. Only tweaked the idle and away it went. Yet myself and others have had to completely re-engineer the tables.