[dog walker]

Anyone have any thoughts on how I might go about hooking one up in my FJ60 with TBI305/700R4/NP208

I'm kinda hoping somone has already gone through this and has some pointers. I need to have this for smog reasons, plus I want the lock up to function correctly. So I don't think burning a new chip is the answer.

Also, I don't have the VSS, but I think it's still on the truck I pulled the computer and motor from, anyone know if its on the speedo cable or is it on the speedo block in the dash?

 

[texican]

It's in the back of the speedo on the donor.
AFAIK your only 2 options are an aftermarket in the speedo cable,or machining a spot like Medusa did on truggy, (not a viable alternative for those without a machine shop in house)
I have donw 3 TBI conversions with no VSS, and notice no difference, all were manual trannys. Jeff Jones broke his off in Colorado and drove his TBI 80 back, then for a couple of weeks til Marks Adapt. got him another one from Oz. The only reason he reinstalled it was his speedo did not work without it.
I guess if it's a DD I would put it on, but would not hesitate or wait on the conversion for it.
Butch

 

[dog walker]

It's in the back of the speedo on the donor.

Thanks! Anyway that I can make that work though? or should I have a custom cable made, then buy the VSS adapter from Painless?

 

[texican]

Jeff I don't think you can make it work, since it is coupled to the electronics built into the speedo, it also has a thing called a buffer that is seperate, but none of the aftermarket use it.
According to one of my friends that is the "master" at our local GM dealership, the VSS only tells the computer when the car is moving so it will know how to control idle when you let off the gas. The reuirements are different if you are moving or sitting at a stop sign, now, Jeff Jones has the Jag engine swapping book that so many swap guys recomend and he says in there it says the VSS also control lean and rich depending on whether the car is moving or not. Jeff also swears his 80 gets better mileage without it??????
I have the best scanner Snap On makes, and have never seen a code related to the VSS (except no speedometer).
That is, when troubleshooting, I have never been directed to check or replace the VSS except for speedo related issues.
Butch

 

[cruiserbrett]

To the best of my knowledge, the "Lean cruise" function of the Eprom/computer was never enabled by GM for smog reasons, so that will not be affected by the lack of a VSS.

the VSS's main functions are to change EGR functions, and torque converter lockup. It also seems to slow the drop to idle when you step off the gas while moving, vs stopped. mine used to (every so often) stall if you rapidly took your foot off the gas when moving, got the VSS installed and it has yet to do it again.

I am not familiiar with the NP208, but is there no speedo cable drive??? If there is I would get the cheap 2 pulse VSS from Jags that Run, with domestic threads and get a speedo shop to make a short cable from the T-case to the VSS and a long one up to the speedometer. Keep the cable to the VSS as short as possible...it can make the torque converter locking and unlocking, as it can be really sensitive to even an ever so slightly jumpy cable...

I ended up having to get a short cable,(and the long one shortened) made for the Toyota threaded VSS(22mm) and it cost alot compared to what a the same cables would have cost with domestic ends....

Just my $.02

 

[EricFJ40]

It seems to depend on the year of the motor how important the VSS is. On the earlier TBI's, 87-92, it doesn't seem to be a big deal. The later models, 93-95, seem to have more problems related to the VSS. The later TBI's also use a 40 pulse sensor rather than the earlier 2 pulse.

On my 95 TBI setup with no VSS hooked up, I have problems with it stumbling at idle when first started. I have to drive it for a couple minutes to get the idle to settle out.

 

[texican]

OK. but the VSS sends reference only when moving, so how could it affect the idle on startup?
Not trying to argue, just trying to figure out how this "could" matter.
Are you sure this is the fix?
Butch

 

[sixty]

I don't have the vss hooked up on my 93tbi either (although it is installed) & get the same cold idle stumble. when the throttle is pressed hard it not noticeable but when creeping from a start it wil hardly run. not that big of deal but I have heard about alot of TBI's having cold running problems w/o the VSS. I need to rehook mine up & see if it makes a difference.

 

[RustyNailJustin]

My VSS is not hooked up and before my PROM was reprogramed it idled weird to. Fast idle then almost die then fast... Once the VSS was taken care of it was all better.

 

[fj40guy]

Another source for the VSS sensor:
http://www.jagsthatrun.com/

Just went to click on the web page with the sensors, but it is fubar'd at the moment.

Butch -- on the VSS sensor, the computer *MIGHT* be fooled into thinking there is a speed sensor at speed out there. Basically with no sensor connected, you have almost 8' of wire. Acts like a attenna. The VSS termination is slightly different using a voltage limited opamp trigger. The long wires, with ignition noise, could trick the computer into thinking you're at speed on a long downhill. To keep the emissions down the computer will kick up the IAC a little. For cold start it would mean some strange idle issues.

One way to TEST this idea out. Just take a resistor and add to to the two end wires. Keep it simple like a 100 Ohm, 1/4 watt. If that solves the idle problem... fine, if not.... you're only out a few pennies.

Tom :usa:

EDIT: Cable mounted VSS units
http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html

 

[texican]

Tom, on 2 of the ones I did they were using a harness from Fuel Inj Specialties out of San Antonio, they are custom with no wiring at all for the VSS, or any of the other stuff you don't use.
Butch

 

[fj40guy]

Tom, on 2 of the ones I did they were using a harness from Fuel Inj Specialties out of San Antonio, they are custom with no wiring at all for the VSS, or any of the other stuff you don't use.
Butch

Hmmmmmmmm????

On those harnesses do you see any problems? Open inputs, at the ECU, could also have the same problem... just more likely to occur with the length of harness wire.

The OBD-II diagnostic port should have a read out of wheel speed (via VSS). So on a 95 or later at least if you saw a reading when sitting there it would give a clue as to the problem.

One thing I hate about "floating input pins" is the minute you go to look at them (looking for electrical noise, the scope probe will load the pin enough so it doesn't show any noise on it!)

For those of you who had "idle problems solved by adding a VSS". What year was your ECU from? (different VSS - either DC or AC signal)

Tom :usa:

Is there a Dallas LSLC meet tomorrow night? Might just have to do a road trip for a little Papa's BBQ.

 

[texican]

The guy at FI Specialties, asks you what you want to run thru the ECM, he then builds the harness accordingly. For instance, on the EGR I always do away with the ECM control of it, and run it "old school".
I use the ECM that came with the donor engine, no prom work at all.
Yes, there is an LSLC meeting tommorrow nite.
Deb will be rollin' thru Round Rock early in the morning, she is in San Marcos with Andrea, she had a little female type surgery done this morning.
Butch

 

[fj40guy]

Hey Butch.

VSS -- what year donor ECU's did you use? Different sensors, so trying to get a better idea what years seem to have more of an issue than others.

Hope Andi is doing good. Hi to Deb. Lack of sleep, and too much rain, so not doing any Dallas BBQ runs tonight. Still hi to the rest of the LSLC folks.

Tom :usa:

 

[EricFJ40]

OK. but the VSS sends reference only when moving, so how could it affect the idle on startup?
Not trying to argue, just trying to figure out how this "could" matter.
Are you sure this is the fix?
Butch

As it was expained to me the computer uses the signal from the VSS to know when to reset the idle air control motor. Without this reset the IAC doesn't know where it is and has to hunt around for a while until it finds where it wants to be. Until it figures that out it can go from wide open to completely shut, causing an eratic idle at start up.