I'm trying to check my 87 924S for vacuum leaks by putting air to the J boot and all I can hear is air escaping by the ISV. None of the posts I read said anything about disabling it to do the check. The engine runs at 1300 cold and warm. I tried putting key to on without starting the engine and also disabling the ISV; nothing changed. Could this be this my problem?

 

I recently replaced my hoses to the ISV, and it didn't appear there is any spring in the ISV to force it closed. So turning on the key would seem to have closed it, unless it needs an actual Run signal to actuate?

Try looking up from under the car, right behind the DS motor mount. You can see the hose out of the ISV to the intake manifold, you can even reach up and feel for air leakage.

 

I tried putting my hand up from underneath, as you suggested. I can feel air escaping but can't tell from where. I did notice the sound of air escaping by the fill cap. When I removed it air was coming up from there. I didn't like that idea and thought it was escaping freely past the rings. A compression check (dry) shows 143-145 psi across the 4 cylinders. Now I am confused??
I'll have to look into the vacuum system closer.
I don't have any history on the car except for the short drive to my garage but the PO did some work on head and belts that was criminally stupid. Ran OK but wouldn't have run long as it was.

 

I'd suggest pulling the intake manifold . You'll end up doing it sooner or later, so get it over with! Everything is easy to fix with it off, and it isn't real hard to pull it. You can pull it with the injectors and FPR and damper still attached if you have a hex wrench that can get at the IM bolt under the damper (ball end helps). You'll need new gaskets and expect to spend a lot of time scraping the old gaskets off. Mark the angle the short double-bent hose out of the ISV fits to the ISV so you can install a new one correctly (it really helps to have a second person when re-installing the IM so you can attach that hose to the IM).

 

Thanks 944Ross. Think your' right. I'll change the hoses and AOS o-rings while I'm in there

 

I'm glad I pulled the intake. The clips on the injectors weren't holding them onto the rail (they were just on the injector) , there is no seal on the dipstick tube( fell over when I took the bolt holding it out) and at first I thought the hoses were tubes ,long overdue for changing. The leak could have been from a few places under the intake.

 

You may have dodged a bullet on the injectors!

My dipstick tube was "puttied in" with some white crap.