Idle too high. How do I adjust

[Shannen Durphey]

It's kinda late, I've been up for a while, but Robert Rauscher had posted to the
archives some very good information of 7747 idle control strategies.

One way to deliver a speed signal to the 7747 in this scenario would be to use
"flying magnet" type crankshaft triggers as used with MSD and other ignition
systems.  The A/C output from the sensor could easily be fed to a DRAC (speed
signal convertor used with the 7747 in many pickups) and the ecm would think the
vehicle was moving as long as the engine was running.  This could be connected
with a switch which is open in P or N (or whatever the marine equivalent is),
and the ecm would see no speed signal in P or N.  A fixed frequency generator
which sends a signal whenever the boat is moving would likely work as well or
better, again activated only when not in neutral.

There are many different 747 calibrations.  You are wise to have it read/looked
at before deciding there is an actual problem.   Some big block calibrations
have some very interesting settings.

Shannen

So if we don't want a speed signal in P, does that mean the sensor needs to be
connected inline with the anchor?



Brent wrote:
> 
> > As far as mounting the VSS, Im wondering about a mechanical tach drive or
> > using a pulleyed mechanism and running it that way. Since we have only one
> > gear, it seems reasonable that using the right pulley size would allow for
> a
> > reasonable VSS signal.
> 
> The VSS has to stop in order for the ECM to enter "idle", so an engine
> driven solution doesn't seem feasible.   You probably should connect the the
> Nuetral/Drive switch.
> 
> > I have attempted to correct the idle issue by disconnecting the IAC, using
> > the suggested methods. This does work. However, it introduces a starting
> > problem. It has a hard time starting. So, Im thinking a chip mod is the
> most
> > comfortable method.
> >
> > I appreciate everyone's efforts on this.
> >
> > Greg
> 
> I believe you are right.  I looked at a few 454 bins and all had a commanded
> idle of 750-800rpms.
> 
> Regards,
> Brent
> <massive snip>
> 
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