90 Tach isn't working

[bostonhatcher]

I've been trying to figure out why the tach isn't working in my 1990 Talon Tsi. I read on http://www.ecanfix.com/users/mdhamilton/ecuconversion.html about the differences between the 90's and the rest and I am stumped. I know I have a 90 ECU, 90 Power Transistor, and a 90 Coil pack. The pictures match up exactly to the site above.

The first problem is that I'm pretty sure I don't have a noise filter. I know it mounts to the intake manifold brace and I just took that off last week and it wasn't on there. I thought maybe if I find where it plugs in to then I can follow the wires to the noise filter but I can't even find the plug for it! I guess if someone could tell me where the noise filter plugs in at I can go from there.

 

[bostonhatcher]

Bump for help.

 

[MrBoxx]

Do not bump your thread. Either someone knows the answer and will chime in eventually OR no one knows the answer and you'll have to look elsewhere.

 

[oldman]

It goes right into the engine harness behind the intake manifold. If you truly have the 90' harness, you can't miss it as there is only one small plug that will fit.

Again, like Eric said, next time you bump again, you will receive a warning as well as thread closure.

 

[Rex2342]

What is the tach doing? When I had a 91 ecu in my 90 the tach would kind of work but would read a decrease in RPM's once under boost. Do you have another way to monitor rpm like a logger? What is the part number on your ecu?

 

[bostonhatcher]

I don't have a logger but there is an aftermarket tach that's wired into the CAS which does work. The stock tach doesn't even move.

I don't see the plug at all on the wiring harness behind the intake manifold. It has to be a 90 wiring harness because it plugs into the 90 coil pack and power transistor. Is there a wiring schematic somewhere so I can just hardwire everything in from the coil pack to the tach or computer (wherever it goes).

 

[Rex2342]

I wouldn't hardwire anything. Hacking the harness always ends up causing more trouble than it's worth. It's kind of wierd that you have no signal at all though. Try taking the after market tach off and tapping into the tach signal from the ecu harness. If you still get a signal from there you move onto the coil and noise filter area. It could also just be a bad gauge cluster.

 

[bmwracing_6]

I have a 91 GSX and my tack doesnt work work all of the time either. I thought it was the gauge cluster. I replace it 2 times and just gave up. On one of the guage clusters the RPM guage would work like every other time I cut the car on. I did swap out my wiring harness because my my harness was mess up and my neighbor tried to rewire it but wired it wrong.