rmoleman

The car (1986 951) was idling very rough so decided to change all the vacuum lines this weekend.

I am in the middle of replacing all the vacuum lines and I find the cycling valve has a broken port.

Now am thinking as long as I have to replace the cycling valve should how do I know the idle stabilization valve (ISV) does not need to be replaced as well.

Is there anyway to test the ISV with the everything disassembled? It would be a real pain to get everything put back together then find out I have to replace the ISV.

rmoleman

After some more searches I am now wondering if I should buy a cycling valve or replace it with a manual boost controller? Opinions?

Spidey944

Not sure on the MBC, have not made that mod yet. But on most vehicles, Ive found that if you can shake the Idle control valve/motor, and it rattles, it's normaly bad.

Stiletto

If you want a replacement CV, I've got one I just pulled off my '86. If $40 shipped sounds fair, PM me if you decide to go that route.

Luis de Prat

Kind of difficult to check the ISV itself for leaks while installed.

One thing you can do is try bypassing at the engine diagnostic test socket it to see if the idle changes for the better. You can do this with a pair of needle nosed pliers, inserting one tip in each of the 2 ports that must be bridged for the bypass to occur (search for "setting the idle").

In my case, when I pulled it off the car, I tested it by capping one port with my thumb and blowing through the other only to find that it leaked air.

Probably could've tried sealing it with RTV as it was expensive to replace, but with the new unit the idle is back to normal and I can forget about it for another 15 years.