missing at 11 hg of vacuum

My car started missing a couple of months ago but only does right at 11 hg of vacuum. As long as you keep it above or below that it runs perfect without any other problems. I've looked in other threads and can't find the answer to this problem so maybe someone could help me out.

This is the first time I've seen this particular problem posted here.

When this happened to me, I searched the forums up & down but didn't find anything either. Mine was at ~ 3 hg vacuum, but the symptoms were exactly as you described. Some days the 'missing' was worse, other days it was milder (but still there). The good news is mine doesn't do that anymore; the bad news is I never found the cause .

During that time, I had replaced my plugs & wires, PCV valve, IAB valve, ACT sensor, ECT sensor, and removed my supercharger to clean out all the crap that gets stuck on top of the lower intake manifold (This was regular maintenance/service, not to cure the problem you described). When I had the supercharger off, I noticed that one of my vacuum lines was starting to split at the vacuum tree, and a couple of other lines were loose (not falling off loose, but not tight to the vacuum barbs either).

Before I re-installed the S/C, I fixed all those loose/split lines and used gear clamps to secure them. Voila!.. no more problems @ 3 hg. Now, keep in mind I still don't know for sure if that was the actual cause (because I replaced all that other stuff at the same time), but I suspect it was.

Good luck.

PS. Please post back if you find the problem... I'm very curious to know what causes this.

Thanks for the info. I'll try checking everything you did and post what happens.