I've been having an issue recently where my vacuum kind of jumps 2-4Hg in almost a controlled manner (i.e. goes from -14 to -10 then 1 second later it's back to -14). I checked most of the vacuum lines with a vac pump and an air compressor @ 10psi(since the car has a turbo). When I got to the VTCS delay valve and blew in it, air blew in both directions. 1 direction was much much more restricted than the other, but I was still able to get a very small amount or airthrough. Would this be enough to cause problems during warmup, and maybe what's causing my vac to jump only on warmup?

Also, when the vac gauge jumps sometimes there's a slight stumble... could this been the VTCS ports closing/opening quickly?

 

A low vacuum reading normally means a partially restricted exhaust/converter. It can only suck in as much as it can blow out. I would'nt trust a vac reading during warmup as a cold engine needs a rich mixture much like the carb chokes that closed off air to the carb on warmup. As far as a stumble i would check the tune/injector/throttlebody/maf cleaning etc.

 

A little confused on your reply...

Maybe I wasn't clear myself... I don't have a low vac reading. At idle my vac sits @ -22Hg. The vacjumpingproblem during warmup happens while I'm driving under no load conditions in 3rd - 5th gear around 2500-3000 rpms (close to when VTCS switches over) only when the car is warming up. When I'm drivingaround town ona normal day-to-day basismy vac isusually -10Hg to -20Hg, while under load, which I assume is normal.

My real question should be about the delay valve... Should I be able to blow air from the black to the green side at all? If no air should make it through blowing from the black to green side, then there is a problem I need to take care of. If this is normal, then I know to start looking else where.

 

http://www.mazda6tech.com/index.php?...4&Itemid=1
Found this.Hope it helps. Disengagement is at 3750 rpm.