ISC switch

[Mike 83 T type]

Does anyone know where to get one. I tried a GM dealer but was discontinued in 92. Auto Zone doesn't seem to have them either. Have not tried pep boys yet. Any suggestions?

 

[Freddie's Buick]

Go thru your local bone-yard. Almost all early 80's GM cars have one.

How do you know your old ISC is bad?

 

[Mike 83 T type]

Im not sure yet. But i know i have to adjust my idle. Some times it rides great and idles smooth. Im going to play with the idle screw and see what i can do but it will stall when im coasting. Or when im sitting at a light and idle pulses after it is warmed up and put into park. Wanted to see if the switch was availible to me before i get started. After the snow melts. Thanks for the reply

 

[Freddie's Buick]

The ISC is controlled by the ECM. Adjusting it is not possible without the proper procedure.

Here is the procedure:

1) With car off, check adjustment of the plunger screw. It should be 5/16". If it is'nt, than remove the ISC and adjust out from it's "turned in" position with a pair of pliers.

2) Next, jumper a wire from the battery to the 'C' input of the ISC plug and the other to the 'D' input plug. This will either retract or extract the ISC plunger. You'd want to retract it first.

3) Now install the ISC but do not plug it back on. Now start the car and allow the car to warm up for about a good 10 minutes.

4) Drive the car up against a utility pole or tree and leave the car in drive. (The pole should hold the car from running you over). Now adjust the carburetor base idle screw to 450 to 500 RPM's in drive.

5) Once the base idle is adjusted to specs in drive, place the car in park and shut it off. Now, jumpering the ISC again you'd want to extract the plunger fully out. Do not plug the ISC back on.

6) Turn the car on and wait a few minutes. It should idle high and the RPM's should read 900. If not adjust the plunger screw to 900 RPM's.

7) Now retract the plunger by jumpering it. Next, shut off the car and plug the ISC back on.

The next time you turn on the car the ECM will be tricked and over a period of time it will adjust itself. It's most noticable when one turns on the A/C. That is when the ISC is needed the most.


Good luck!

 

[Mike 83 T type]

Thanks for the help.