View Full Version : Vacuum Leak??

Wicked SC
12-15-2002, 03:07 AM
Quick question (I think my SC might have a vacuum leak).

When you guys turn on your A/C, do your SC's lose vacuum?

My car is acting up. After it warms up, when it's idling (like at a red light or stop sign), once in a while the RPM's will drop to about 400 and the car will stumble a little bit. After a second or two, though, it will return to normal. Also, when I turn on the A/C, sometimes it will do the same thing (drop RPM's and feel like it wants to stall). Again, after a few seconds (or if I jab the accelerator), the car will return to normal. The weird thing is that with the A/C running, I only get about 13 inches of Mercury of vacuum at idle.
Other than that, the car runs OK. I get 19 in. Hg of vacuum at idle (with A/C off, of course), and about 12 psi's of boost at WOT.
Plugs (Motorcraft double plat's) and wires (Magnecores) are about 6 months old.
Other people have also suggested an Idle Air Control Valve on its last leg. Any opinions?? Thanks.

12-15-2002, 09:39 AM
sounds normal to me ..figured it was just the load of the Ac clutch kicking in putting more load on the motor... takes a few ponys to turn that compressor and more load = less vacuum ..

12-16-2002, 01:15 PM
When mine started doing that years ago, it was the first signs of engine mount decay. Of course, I didn't know it at the time, just scratched my head and went along turning the A/C off while at stoplights.. Of course then the A/C itself died, so it wasn't a problem anymore ;)

Wicked SC
12-17-2002, 03:05 AM
Thanks for your responses. The funny thing is that I just replaced the engine mounts a couple of weeks ago. But now that you mention it, I haven't used the A/C since then. Maybe it's not doing it anymore (I can't check right now cause the radiator is Kaputt!). I'll check this weekend after I replace the radiator. I just wanted to check if it's normal to lose vacuum when you turn your A/C on. Thanks, guys!

12-17-2002, 06:17 PM
This could also be due to the AC compressor starting to die on you. The closer the AC gets to dying the tighter the pulley will run, and the more friction the belt will experience.

12-18-2002, 01:44 AM
Wicked, if you have'nt already bought a new rad I have one thats only a year old. Say....$50.00