Ok from what I have read the VSS is needed for: Lock-up converter, EGR, charcoal canister, electric fan, Idle speed and fuel air ratio. (Did I forget anything?)

I am running a painless harness with a closed loop set up (no VSS).
I have made the following modifications:

-Lock-up converter controlled by Superior hydraulic kit.
-Running a mechanical Speedo
-EGR block-off plate
-Charcoal canister is a fuel tank vent only
-Electric fan is controlled manually
-Idle speed adjusted, works fine

The last thing is the air/fuel ratio. How critical is the VSS towards the CPU and fuel/air adjustments? With the above modifications does the CPU have anything else left to make adjustments to?

I am trying to figure out what components the computer controls in regard to the VSS fuel/air ratio to find out if there is anything else that needs to be corrected, or is it fine the way it is.

 

What ECM are you using? I think it matters.

 

The ECM # is 1227165 for /87 5.7 TPI (Auto)


I believe I have changed everything that the computer does with the VSS information ie: Emissions, lock-up converter, Speedo, and Idle.

I need to find out what the computer controls in regard to the fuel/air mixture to find out if I can some how change that also, or even if it is necessary. I have read that the VSS makes changes and adjustments to the EGR, charcoal canister purge, idle, etc.

If that is what they mean by fuel/air mixer it does not apply to me, as my set-up is a none emissions set up, mechanical Speedo, hydraulic lock-up converter etc.

I think the O2 sensor will give the computer whatever informtion it needs in regard to the fuel air mixture, but I will not be able to figure it out unles I can find out what things are moved or ajusted to change the fuel/air mixture on my TPI motor.

 

In my limited understanding of the earlier TPI ECMs, I believe that the VSS input has little if anything to do with mixture control except in DFCO enable and disable points, knock detection enable MPH, and eventual fuel cutoff. If you're not using HFSM, the VSS may not be necessary. I believe the VSS input is more important for Speed Density systems, however.

 

Check to see if the 165 has a parameter for minimum speed before knock retard occurs, as Vader suggested. If its set to 2 or 3 mph, then even if you get massive spark knock, the ecm won't pull timing until it reads 2 or 3 mph. If there is no VSS, then it will always read 0mph, hence no retard.


I know this is a problem on speed density, not sure about your 165.

 

Ok first off thanks for the help

I am still learning the TPI computer stuff. What I think you are telling me is that without the VSS, the computer thinks the car is in park. If the computer thinks the car is in park, it will not adjust the timing.

Is there any test I can do to find out if my computer is adjusting the timing as I drive?

Can the computer be made to think the car is moving over the, “3 MPH parameter” and therefore make timing adjustments?

If the timing is found not to be advancing or retarding is there anything that can be done that will allow the computer to make changes to the timing other than put the VSS back in?

This question may sound really stupid, but if I used a carburetor style H.E.I distributor (with a harded cam gear) can the T.P.I. fuel system still be made to work off the computer?

What is DFCO, and what is HFSM ?

 

There are a lot of options for VSS, at this point it sounds easier to just run it than try to work around it.

If nothing else, it can cause problems with IAC when you let off the gas and the vehicle is moving. You may or may not end up with stalling problems.