: 81 deville tachometer, idle gas

08-13-07, 04:27 AM
hi guys

I've a question.
some time ago i asked because my cadillac stared very hard, but it was a broken ECM, since i got a new one the car runs nearly perfect.

now i've a problem with my idle gas... the car idles too low.

i drew in the screw from the ISC-motor because before the idle gas was much to high.....

now i want to have the correct idle gas, like described in the service manual but i dont know where to connect a tachometer for watching the RPMs of the car. in the book there is only written, that i should connect to the distributor but i dont know where.

then according to the manual i should run the car with 1500RPM and touch the ISC-motor to let it retract, then i should disconnect the ISC and should bridge A and B on the ISC-connector

okay then the ISC-screw should not touch the throttle and then the TPS sensor should have 0.5 volts with about 350RPMs

but thats the problem, without a tachometer i dont know how to do this procedure, and maybe somebody can help me in describing how to install a tachometer.

thanks a lot in advance

08-13-07, 09:44 AM
Should be - to ground, + to positive lead on coil.

08-13-07, 05:14 PM
hey thanks for the quick answer..

yeah i know the negative to ground and positive to the connector on the coil, but on my coil there are only written B and an other letter but not "tach" or something else that could be a hint for me to connect it correctly...

i dont know where exactly to connect on the coil thats my problem, and maybe someone did it some time ago and can tell me where to connect it

but thanks a lot

08-13-07, 05:24 PM
Did a little more Googling for you and found this:


Either go to the TAC terminal on the distributor or to the C- terminal/wire, which is typically a brown wire.