Idle too high. How do I adjust

[ZZZ Temp-Gold]

This boat has a stern drive and has a 1.50:1 ratio and the stock '747 ecu
seems to do quite well in powering the vessel. 

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. Im certain this could be accomplish with some of the
suggested electronic methods, but, unfortunately, I am not versed in
electronics. I can follow diagrams though, if one where available.

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


> ----------
> From: 	Pat Ford[SMTP:pat at istop.com]
> Reply To: 	gmecm at diy-efi.org
> Sent: 	Wednesday, September 12, 2001 11:53 AM
> To: 	gmecm at diy-efi.org
> Subject: 	Re: Idle too high. How do I adjust
> 
> most small boat ( automotive sized engines) use the Borg-Warner velvet
> drive transmissions. these tend to be 1:1 in drive and either 1:1 or
> 1.1:1 in reverse ( I have a fsm for them somewhere)
> There is a neutral safety switch as well. 
> 
> Dan Griffin wrote:
> > 
> > Bottom line: Does ecm use vss to determine eng. load?? If so I dont see
> how
> > a car/truck ecm could be made to easily work on a boat..I say 14.7 to 1
> is
> > way to lean, even at steady cruise, ( 19-23 mph hull just planing)...eng
> > load for a car is much less...If only map, tps and rpm are used I think
> I
> > could see how this might work though...
> > what/how to send vss a signal though? mount a speedo cable to prop? Or
> the
> > magnetic sensor type, I dunno if  that'll work underwater though? prop
> rpm
> > is same as eng rpm (I think)...In neutral prop shaft is the only shaft
> not
> > in motion..You want neutral switch hooked to gear selector..somehow...
> > All unused tables in the bin would have to be zeroed...I see lots and
> lots
> > of chip burning here unless you get really lucky, ( if its right the 1st
> > time Id buy a lottery ticket)
> > Dan
> > ----- Original Message -----
> > From: Jay Vessels <jwvess00 at home.com>
> > To: <gmecm at diy-efi.org>
> > Sent: Tuesday, September 11, 2001 6:59 PM
> > Subject: RE: Idle too high. How do I adjust
> > 
> > > Hi there!
> > >
> > > On my truck ('87 2.8V6 TBI 1227429 ECM) you can set base idle speed
> with
> > > the following method:
> > > Key off, short ALDL pins A&B.  Key on for 30 seconds or so, then
> unplug
> > IAC
> > > with the key on.  IAC pintle should be fully extended here.  Start
> engine
> > > and adjust base idle speed (minimum air).  Turn engine off.  Key on,
> > adjust
> > > TPS voltage to spec. (0.50 volts +/- .05V seems to work for most
> cars).
> > If
> > > the voltage was way off (i.e. you moved the idle screw a long ways)
> then
> > > you might want to repeat the process until you get a base idle speed
> you
> > > like and a TPS idle voltage in spec.  This also seems to work for
> Dad's
> > '86
> > > Caprice ('85 F-body TPI system, '85 ECM number slips my mind).
> > >
> > > This did not work for my '84 Cavalier Type 10 convertible (2.0I4 TBI,
> > > unknown ECM).  It had a plug that you were supposed to install in the
> air
> > > horn of the TBI to block the IAC before you set minimum air.
> > >
> > > When I got the car, it idled at about 2000 RPM and slammed into gear.
> I
> > > replaced all the gaskets, vacuum lines, and the IAC to no avail.  I
> could
> > > not adjust the speed lower with the idle speed screw.  In a fit of
> anger,
> > I
> > > removed the IAC and pulled on the pintle.  It almost came all the way
> out.
> > > I threaded it back in so that the TBI's pintle seat itself would push
> the
> > > pintle in as I reinstalled it.  Started the car, idled fine.  I guess
> the
> > > IAC was somewhat retracted and the ECM never commanded enough steps to
> > > fully seat it.  Either that, or it was stuck (albeit new) and my brute
> > > force method fixed it.  Try this at your own risk.
> > >
> > > On my truck, I don't have the VSS connected at all and the ECM is
> wired
> > > such that it is always in Neutral.  It idles fine and fuel economy is
> > > decent.  What benefits would I gain from attaching the VSS signal
> (didn't
> > > have a VSS when I converted to TBI, now I do since installing the
> cruise
> > > control)?  Currently set up like it is to disable EGR complaints.
> Would
> > > pulling EGR code out of the chip and connecting the VSS signal be a
> better
> > > solution, or just more work?
> > >
> > > Jay Vessels
> > > 1982 Chevrolet S-10 Sport, 2.8V6 TBI
> > > 1994 Chevrolet Cavalier Z24 Conv., 3.1V6 MPI
> > > http://www.vessels-clan.com/jay (now W3C compliant)
> > >
> > > At 05:22 PM 9/11/01 -0500, you wrote:
> > > >
> > > >> As far as connecting a VSS, Couldn't I just connect it or would I
> have
> > to
> > > >> mechanically power it as well?
> > > >>
> > > >> I dont see the connection logically between the VSS and idle, as it
> > idles
> > > >> perfectly, other than too high for the boat. In the vehicle, 800
> would
> > be
> > > >> very suitable.
> > > >
> > > >You could likely connect it once and give it a signal > 36 mph (isn't
> > that
> > > >right, fellas?) to allow the IAC to reset itself, then disconnect it.
> > > >Problem is that the IAC baselines itself to certain numbers of
> "steps"
> > > >from being closed...then after some period of time the ECM attempts
> to
> > > >adjust to a particular RPM, given other parameters. Other parameters
> > > >include stuff like decel, dashpot, temp, A/C, PNRDL, etc. My car
> would
> > run
> > > >at 2500 RPM for a few minutes before it idled down, and it never did
> make
> > > >it to true idle speed. IAC didn't know where "closed" was after I
> took
> > > >the TBI apart for cleaning. Sounds like you don't have that
> > problem...yet.
> > > >
> > > >If you don't have the ability to burn an EPROM, that idea of blocking
> IAC
> > > >and adjusting idle speed with a screw looks better and better. I
> won't
> > > >pretend to be anyone that is worthy of burning chips for people (can
> you
> > > >say engine go poof?), but if your calibration (the 4 letter code) is
> one
> > > >of those listed in the bin_library email me directly and I'll give it
> one
> > > >shot in the name of neighborly help. Today seems like a good day to
> offer
> > > >some of that.
> > > >
> > > >-greg
> > > >
> > 
> >
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