MPS testing and where get rebuilt, Slight loss of vacuum after 5 min ? bad MPS Options

[jsf322]

I just checked my MPS because my car is running rich, burns a lot of fuel, and idles very poorly especially when warm. The CHT was bad and I replaced that. IT improved the stalling I had before replacing it, but the car is still rich and idles very unpredictably. I put 15mm Hg on the MPS and it lost about 1/2 mm in the first minute and 4-5mm within 5 minutes. Would that be considered a bad MPS. If so does anyone have experinece with rebuilt units from AA or Preformance Products. AA is about $40 cheaper. Thanks for any input.

[BMXerror]

Being a recent Bleyseng customer that is having the same problem, I'm going to chime in. I doubt that 8 in. Hg in one minute is causing that bad of a problem. I pumped my old MPS up to 20 in. Hg and it leaked all the way down within a minute. The MPS was obviously bad, so I replaced it and the car ran only a TINY bit better. It will idle without flooding out now(which it wouldn't do before), but it's still SUPER rich. There's still other problems to be resolved.
So before spending the 200 bucks, I would check what I've since found out is the problem with my car. T in a vacuum gauge to your line going to the MPS and see what kind of manifold vacuum you're pulling at an idle. I think it should be around 20ish. If it's lower than that it means two things. A: you have a vacuum leak somewhere between your throttle body and the heads(or maybe in the hose itself), and B: your MPS is getting a false reading to meter the fuel by. You can also manually pump the MPS up to about 20 in. Hg and see how it idles (which may be a bit more difficult if it's leaking down). Make sure to plug the loose MPS vacuum hose when you do this. If it runs well, this should eliminate any electrical fault between the MPS and the ECU as well as a fault with the ECU as well. Of course, all of this is assuming proper fuel pressure. Check that first. I'll shut up now.
Mark D