To check the vacuum modulator for a faulty diaphragm, you can do the following:

1) Disconnect the vacuum line from the intake manifold. Inspect for any ATF in the line.
2) Connect a vacuum tester hand pump to the line and pump it down. It should hold the vacuum. If it doesn't hold vacuum then either the line or the actuator has a leak and needs to be replaced.
3) With the vacuum line off, rub inside the vacuum elbow with a Q-tip. You are looking for signs of red dye present in ATF.
4) You can leave a small piece of cotton in the vacuum elbow for the purposes of seeing if ATF fluid is making it past the modulator diaphragm. Cigarette filter works good too.


Good luck!



-tp