Idle too high. How do I adjust

[Pat Ford]

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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