VSS

[Shannen Durphey]

There are VSS units available which connect to the speedometer cable. 
In 1989, there were THM 400 trans used in pickups with fuel injection
which had a VSS.  You would need to go to the dealership and to
determine that the conversion is possible, and which parts are needed.

Guenther,Max wrote:
> 
> What do you do if you dont have one?  Can you put one in a turbo 400?
> 
> >----------
> >From:  rauscher at icst.com[SMTP:rauscher at icst.com]
> >Reply To:      diy_efi at efi332.eng.ohio-state.edu
> >Sent:  Wednesday, January 27, 1999 9:00 AM
> >To:    DIY_EFI at efi332.eng.ohio-state.edu
> >Subject:       Re: VSS
> >
> >
> >
> >Mike Pilkenton wrote:
> >
> >>Could someone tell me what functions the VSS signal might affect in the 92
> >>3.1L V6 Camaro ECM.  The motor/ECM came off a manual tranny car and my
> >>project car application won't have this signal available unless I install an
> >>aftermarket speed sensor.  Do I need this signal?
> >>
> >>Mike
> >>V6 Opel GT
> >
> >
> >Mike, there is a ton of information in the archives, to go the DIY EFI home
> >page and follow the links. Personally, I believe that the VSS is important,
> >there is also info on what the signal looks like and some ideas and also
> >off the shelf solutions to this.
> >
> >http://efi332.eng.ohio-state.edu/diy_efi
> >
> >I got the following from there:
> >
> >the following text is from:
> >http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html
> >
> >-------- quoted text from webpage ------------
> >
> >Without a VSS, the Chevrolet Fuel Injected engines will not run correctly,
> >and they will not pass a smog test.
> >
> >Basically, the VSS tells the ECM how fast the vehicle is going. Most
> >people think the VSS is only used for the lock-up torque converter. The
> >VSS is also used to control the EGR valve, the charcoal canister purge
> >valve, the electric cooling fans, idle speed, and air/fuel ratio. This is
> >all explained in the Chevrolet shop manuals.
> >
> >It must be emphasized that the VSS is used to control the idle speed when
> >the vehicle is moving. Without the VSS, a vehicle may have stalling
> >problems under certain conditions.  Needless to say, this is dangerous.
> >Raising the minimum idle speed with the adjusting screw can eliminate
> >stalling, but the engine will still not run optimally without a VSS.
> >
> >A lot of people think that running "closed loop" is best for fuel mileage.
> >Closed loop simply means that the oxygen sensor is being used to monitor
> >the fuel/air ratio. Some of the Chevrolet fuel-injected engines are
> >programmed to run lean under certain conditions (called "highway mode") to
> >improve fuel mileage during steady cruise conditions. Without a VSS, the
> >engine computer (ECM) will not get the correct signals to run the engine
> >for best fuel mileage. There are a lot of programs in the ECM that depend
> >on the VSS. For best operation, the VSS needs to be connected and
> >functioning.
> >
> >-------- end quoted text from webpage ------------
> >
> >Here is a list of things affected by the VSS sensor.  This list covers
> >three different engines, two of them 4 cylinder TBIs.  All three
> >applications are from the same era as the 1226867 2.0 TBI.
> >
> >Code 24
> >TCC lockup (auto)
> >Upshift light (manual)
> >IAC position learning (above 30 MPH)
> >Cooling fan control (not used in these applications)
> >Determine if manual transmission is in gear (compare VSS vs RPM)
> >Disable some idle speed control if manual in gear (see previous item)
> >Disable idle learn if moving
> >Enable idle learn if moving with manual in neutral
> >Prevent DecelFuelCutOff if manual in neutral
> >Prevent DecelFuelCutOff at very slow speeds
> >Top speed limiter (not used in these applications)
> >
> >The third application adds one more item:
> >
> >Amount to open IAC and rate at which to close it upon throttle closing
> >
> >Note - the idle speed control logic is a rats nest of complicated code.
> >It is hard to figure what really happens.
> >
> >--
> >
> >
> >