Vehicle stalling after Speedcal install

[gunfish]

I had 4:10's installed in my '95 GT and I had a speedcal installed a few weeks later to correct my speedometer. Since then the speedometer doesn't act smoothly, it will stay at zero for a while and then jump up to the speed you are going, and when you are slowing to a stop it will sometimes jump up for just a split second to 70-80mph.
I have been having a randomly occuring stalling problem at stoplights, and I am wondering if the computer uses input from the VSS to determine idle settings. I just took off my IAC valve and cleaned it, but I still have the same problem.
Anyone familiar with how the VSS works?
Thanks, Glen

 

[95BlackTan50]

For the speedometer not acting smoothly, could the VSS sensor be not completely seated into the drive gear? There's also a forked bracket that holds the VSS into place. I'm not sure if it makes a difference, but it can be put on backwards which may prevent the VSS from going all the way in. I would also check the connections to the speed cal and the harnesses. Installation requires the connectors to be disassembled and reassembled and it could be that one of the pins was not engaged completely. Also make sure that all of the connections are clean.

I'm not sure how that would lead to a stalling condition. Does it stall as you are coming to a gradual stop at a light or does it stall after you have already come to a stop?

 

[Stanger007]

I have a SpeedCal as well.

My speedo needle does a little crazy dance and reads very high every so often - I think I've traced it to being a problem with the gauge cluster. When the speedo is reading incorrectly, my twEECer datalogs still indicate the correct MPH.

What you can do is check all the wiring for shorts. The SpeedCal wiring is relatively simple to trace out starting from the tailshaft of the transmission.

The EEC has several tables that control the transmission's functions via reading the MPH. I would expect that given an improper MPH signal, some strange things may very well happen.

In an unrelated note, how did you get the SpeedCal wiring into the car with your automatic shifter?

Wes

 

[Bosko5.0]

I would first check the vss gear, then the connectors, then the wiring.

The only thing myne does wrong is when coming to a stop fast, at 5mph the needle will just drop but when coming to a stop slowly its fine.

 

[94-302-vert]

I thought the speedcal was only for manual trans models in the 94-98 years?

I bet changing the signal is creating a problem for the trans controller which is probably feeding bad info to the engine computer...

 

[95BlackTan50]

I thought the speedcal was only for manual trans models in the 94-98 years?

My AODE worked great with the SpeedCal and 373's.

In an unrelated note, how did you get the SpeedCal wiring into the car with your automatic shifter?

I drilled a small hole in the tranny tunnel and ran the wires through that. I had to take the connector off, feed the wires through the hole, then put the connector back on. It wasn't too bad. You just need to be careful taking the connector off.

 

[gunfish]

Thanks for all the replies, guys. It stalls when coming up to a light slowly, or sometimes when taking off. Some days it doesn't happen at all, and other times it will happen at a couple of stoplights in a row. The only constant that I see is that it happens when the speedometer flares up when I'm going slow.
I bought the speedcal, found a tech article describing how to install it with the AODE, and took it to a shop to put it on. I took it back to them when I saw the speedo jumping around, they said the speedcal is probably defective and would charge me to take it off and put another one on.
I think I'll put it up on the ramps this weekend and try to see if something looks wrong.
I was just wondering whether the air/fuel mixture could be being affected by the VSS saying I'm doing 80mph when the speedometer flares up while doing 5mph coming to a stop.

 

[Bosko5.0]

it may be that it is defective

it might be doing that Because I thought a couple of the eec's function like
fuel vs. speed.


where did you buy it from?

and I put my wires through the shifter hole.

 

[Stanger007]

Speak of the devil, my speedo acted up again today while I was going to work. I happened to be datalogging and noticed that my EEC was also getting an incorrect reading.

I unplugged and checked all the connections to the SpeedCal under the car today and all looked fine.

Bosko, I'm not aware of any tables that affect the spark or fueling that are MPH based. All of our tables are RPM and LOAD based that I know of.

gunfish - the SpeedCal is a very easy install/removal if you want to tackle it yourself, just jack the car up on the driver's side and you can get to everything quite easily. I'm curious to see if removing it fixes your stalling problem.

Wes

 

[GT_green_GT]

i have a speedcal with my auto. i took off the bezel and tucked it way back in there and ran the wires to it. but i havent experienced any problems with mine at all. definatly make sure all the dip switches are fully engaged where they are suppose to be. and makre sure all connections are tight.

 

[95BlackTan50]

The transmission shift schedule in the EEC is based on Throttle Position and VSS. A higher VSS reading will make the car try to shift to a higher gear. I don't know if it happens fast enough to make it stall but it may be a possibility.

I agree with Stanger007 that the SpeedCal install is pretty easy as long as you can get the car up high enough to work comfortably. Just be gentle disassembling the connectors.

 

[gunfish]

Just an update on my stalling problem. Although I cleaned my IAC valve, it is what was making my car stall. I unplugged it and adjusted my idle speed up to about 800rpm, and the car runs smoothly with no stalling or hiccupping anymore. I'll get around to replacing my IAC valve shortly, but in the meantime the car is running good again.
Thanks again for all your help and ideas guys.