Losing Ground?

[Zachary Lawson]

Well, that's interesting because the tachometer and the ECU both get their signal from the negative post of the coil. So, in addition to whatever is going on with your connector, you should check connections at the coil and ballast resistor. You might have a loose connection there.

It could also be that your ignition module is going bad. That will cause your tachometer needle to jump around too.

I'll try that tomorrow. If the ignition module was going bad, would it make the idle rough as well?

[Zed Head]

It's hard to diagnose a bad ignition module. I just suggested it as a possibility. Actually though, I'm not sure what you mean when you say the tachometer ("tick hand") isn't working.

Looking back at all of your symptoms, they're kind of strange. The tachometer and some of the lights stop working at the same time? When you say "working", do you mean the needle doesn't move, or it moves erratically or the light in the tachometer isn't on?

There is a large ground wire connected to the battery negative terminal. Is it intact on your car? Probably best to take a meter and confirm good grounds everywhere.

[FastWoman]

Interesting observation by Zed! Yes, ignition failure would similarly result in EFI failure. The EFI only knows when to squirt fuel by counting sparks. You might have a bad pickup or connection. An IM failure is usually either all or nothing, OR it's manifested by stumbling at high RPMs.

[Zachary Lawson]

It's hard to diagnose a bad ignition module. I just suggested it as a possibility. Actually though, I'm not sure what you mean when you say the tachometer ("tick hand") isn't working.

Looking back at all of your symptoms, they're kind of strange. The tachometer and some of the lights stop working at the same time? When you say "working", do you mean the needle doesn't move, or it moves erratically or the light in the tachometer isn't on?

There is a large ground wire connected to the battery negative terminal. Is it intact on your car? Probably best to take a meter and confirm good grounds everywhere.

Everything in the car works except the tachometer and the dash light above the heating controls. These only work sometimes. The tach only works about 10 percent of the time when I first get in my car. It works perfect when it is working. Otherwise the other 90 percent of the time, it doesn't even move. The small ground wire off the negative battery post is cut and not connected to anything.