90 CAS RPM Signal

[misterjose]

i made a thread but i think people were confused because i asked for so many things.
i installed my gm mas to my UICP and the maft is ready to go.
but im having a problem connecting the WHITE wire from the MAFT.
i have a 1990 talon and our CAS is not the same as the 91+
there are only 4 wires from our cas which plugs on the firewall.
which wire can i tap in for the RPM signal so i can finally use my MAFT.
thank you
i will include a picture of the CAS wires that gets plugged on the firewall.
i hope someone knows what I'm talking about because I went through about 200 post last night looking for an answer.

 

[Usatuff]

Pin #2. I think it is the smaller gauge black wire

 

[90tsiPA]

The black wire pin 2 is how mine was hooked up. I was going to go and take a picture but my car has about 8-10 inches of icy snow in it.

 

[misterjose]

okay i don't know which pin is which. these are the wires that connect to the cas which is connected to the firewall.

black or yellow or black and yellow jk.

http://www.dsmtuners.com/forums/attachment.php?attachmentid=118238&stc=1&d=1296501912

 

[silicosys4]

I'm in the same boat, I have finished wiring everything for the 1g maft, but I'm trying to figure out where the white wire goes. The plug from the cas at the firewall has four wires, a black, white, yellow, and red. Which wire do I tap into?
The 1990 is different than any other year cas, I believe.
The first picture is a close up of the cas plug, I believe Its the middle one.
The second picture is further away so you can see where in the engine bay I'm muddling around.

 

[dberry]

did you ever figure this out? because im in the same boat as u

 

[kchaazz]

See the plug Ive circled in red? This is the plug used to attach a tach to monitor RPM when setting the timing advance and Idle speed. Whats to stop you from simply crimping or soldering a spade to the MAFT wire and plugging it right into here instead of hacking up the sensitive CAS wiring??

 

[dberry]

alright i tried tapping into that wire, but my tac started jumping up and down a bit

do u know what color wire to tap on the cas? i tried what you suggested but it didnt work correctly, in seemed to interfere with the tac signals

 

[kchaazz]

Hmm, I suppose that plug will only allow you to tie in a tachometer and nothing else, or that the MAFT is generating the interference somehow and perhaps putting a diode in line between the RPM plug and maft will fix it. Are you familiar with diodes? These basically only allow current flow through one way. You would put the anode side of the diode into the tach plug, then attach the cathode side of the diode to the MAFT wire. Just mock it up and see if your tach works properly with this on there. Diodes are very cheap and you can get em at Radioshack.
I mention this because I am unable to find any info on installing a MAFT on the 90 DSMs. If you have a portable tachometer, you can find the RPM signal wire on the CAS by putting a probe on the signal wire of your portable tach and then, with the car running, put the pointed end of the probe through where the wire comes out of the back of the plug on the cas on each wire until you get the one that gives the tach a reading.

 

[dberry]

i am familiar with them to an extent but i will give it a shot, the tac was juming about 200 rpm, i appreciate the advise