Well, I had to change the rotary select valve behind the AC the other day, and I forgot to hookup one of the wires that go from the vss to the SGI-5 box while I had the console apart. When I started the car, the speedometer obviously didn't work, but the funny thing is my idle problem that I have been trying to solve for a long time went away. The engine used to climb in rpm to about 1500 or 1600, then slowly go back down to 700 every time I would either step on the clutch, or leave it in neutral.

When I hooked the wire back up so my speedo would work, it started idling bad again. Just to be sure, I took it back off, and its idling fine now.

Can anyone explain what the hell is going on here...I don't see a relation between the vss/ and idle speed.

 

Did you steal my car beacause I have the same friggen problem. I have a 91z with the t56 and I am running the SGI-5 box. I was having problems with the speedo jumping around at idle so I tried a different OUT on the box. Well, it was the wrong one and now the speedo dont work at all but my car idles at 600rpms again. when the speedo was hooked up and working, the car would idle at about 1000 to 1500rpms. Now when i stop at a light though, the car sometimes shuts off. maybe cause the idle is set to low. I did not twist the wires as per the directions and maybe this is why I am having this problem. Its to cold to crawl under the car in the winter to twist some wires so I will wait until the spring. Please let me know if you get your fixed.

 

Well, I've had the wiring done temporarily until I got everything sorted out, so I just have the 12v wire for the SGI-5 box stuck in the terminal for the hatch motor at the connector for what used to attach to the neutral safety switch. If I try to get my 12v from the terminal that brings current to the reverse lights at that same connector, the speedo goes crazy even when I'm not moving. It'll climb to about 80 mph or so.

I also tried getting power from the wire that supplies the radio with 12v, but the same thing happens, the speedo goes crazy.

Anyone else running the SGI-5 box....where are you getting 12v from?

 

I am runningmy 12v right out of the fuse block in one of the IGN blocks

 

I called Dakota Digital yesterday, and I spoke to one of their tech support guys. I explained everything thats going on to him, and he had no explanation for whats going on. He spoke to their engineer, and still no ideas.

I didn't twist the wires when I installed the box like I'm supposed to, but that should only cause the box to pickup interference from the ignition system. That should be noticeable in the speedo, and thats not happening. I'm gonna try to twist them anyway when I have time, but I really doubt that would do anything.

Please....If anyone has any ideas....I could really use some...

 

I'm running the SGI-5 box and I don't have a problem like you guys are describing. I ran the power for it from the fuse box, that's just temporary until I rewire it better. I also did twist the wires like Digital Dakota recommended.

 

I am not familiar with the Dakota box but I can say that if the stock ECM sees funny signals from the VSS it can affect idle speed.

For instance: When idling with the car moving forward, even in neutral, the ECM will raise the idle speed until it shows an "all stop" signal from the VSS, at which point it drops the idle down to whatever is normal for your car.

Is it possible that your box is actually INTRODUCING an errant signal into the VSS system that the ECM is interpreting as forward movement and reacting accordingly?

The VSS is nothing more than a spinning magnet that generates an analog voltage sine wave in the 2 signal wires. This sine wave is than converted into digital inside the ECM so the ECM can reference it for various things, including idle speed.

 

BottledZr28, would you by any chance happen to be running a chip from a manual car?

Just out of curiuosity, I tried to put in the old chip, as I had used one off a T5 car when I did the swap. Anyway, that fixed my problem. I still don't know why that was happening, but that was the issue.

 

my car use to have 305 T-5 in it. I put a 350 t56 in and went to dealer got a 350 chip. Then I put a ED Wright stage 2 piggy back chip in it. Do yo uhtink that the 350 chip is giving the ECM a problem?

 

I don't know what to tell you man. I just know that the manual chip was causing the engine to idle high when it was getting a signal from the vss. If i disconnected the SGI-5 box, so the car didn't know how fast it was going, it would idle fine. With the stock automatic chip, it idles fine even with the conversion box hooked up.

 

So what are you saying for me? I have a 350 chip for a 91z28 and those only came with an automatic.