Obviously, i have low vaccume How to fix??

Now, i've postd before that i have about 16- to 17 lbs of vaccume at idle at about 1000 rpms. Now, My tps is not adjusted exactly correct, so the ilde fluctuates to about 100 rpms above 1000, hence the erratic 16-17 lbs of vaccume. now, i'm planning on replacing the uppser intake gasket, the IAC gasket, and the TB mounting gasket. now what else should i replace if the vaccume leak is actually coming from somewhere by the upper intake?? I've checked all of the vaccume lines, they are all tight. also, i have a seperate question. i get about 15 pounds of boost MAXIMUM. I checked all of the vaccume hose routing, and i discovered something wierd. the BCS is disconnected. the vaccume line from the first(tward the rear of the compressor) port on the turbo goes around to the two outlet fitting on the compressor housing. (the one you plug when you install the Gillis valve) the other side of that port goes directly to the waste gate actuator. Could that be why my car only gets 15 Lbs of boost max?? there is absolutely no form of boost controll on my car yet, but i have a homemade control valve that I will be instaling soon. i just want to figure out why i have a vaccume leak first, and figure out if my turbo is shot because of the bypass of the BCS. HELP!!

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87 Tubocoupe, Light Regatta Blue, All Options incl. Leather; 2.5" exaust, Dynamax super turbo mufflers w/3"chrome tips, MSD 6AL, Blaster2 Coil and wires, Homemade adjustable boost valve.
"The stage is set, the orchestra engaged.... it's now time to see if you can dance."

What gauge are you using to determine that you only have 16-17 inches of vacuum? Have you checked it against a 2nd gauge? Before you tear everything apart, determine if you actually have a problem and then try to isolate it (not always possible). Get the TPS and idle corrected before you do anything else. Lots of things can cause low vacuum - late valve timing and late ignition timing are two. Have you checked these?

If all the above check out and you still have a problem then hook the gauge to the fuel pressure regulator port on the upper intake and disconnect the big feed hose to the vacuum tree, same fitting as the FPR port and cap it off. This isolates the TB, upper and lower intakes from the vacuum tree and it's various subsytems. Does your vacuum reading go up? If yes, then you have a leak at the tree or in one of it's subsystems. If NO then the problem is with the engine it self.

Let us know what you find.



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NATO Member. it's not a vice, it's an obsession
Letting the cat out of the bag is a whole lot easier than putting it back in.
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm

There are a ton of places for a vacuum leak to occur: intake manifold gaskets, TB gasket, all vac lines, etc. Even the TPS, EGR or IAC gaskets could be leaking.

Any of the vac lines could leak, the most obvious one is the line to the wastegate, since it sees so much heat from the turbo and exhaust manifold.

Even if the bypassed BCS damaged the turbo (which I doubt) it should not affect your vacuum at idle.

How is your vacuum while driving (accel and decel)?

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86 TC, 73 Austin Mini, 72 Austin Mini Van

Click here to beat a ricer.

My vacume at acceleration is steady, until boost of course, and lets see.... when i let off the gas in 5th gear at about 70 mph, the vac reading drops to about 20-22 lbs of vac. is that about correct? See, i took off the IAC to clean it, and i didn't replace the gasket; just put the old one back on. TPS gasket?? you mean the small rubber thing inside the throttle body?? Also, i'm going to replace the vac hose to the wastegate, pretty much the only old vac hose in the car. another possibility is my guage in my pillar mount ( Autometer boost/vac guage) may be leaking by the fittings, because i didnt use any tefflon tape on the threads....I'm guessing Ill get at least a couple of LBS of vac back from that stuff.

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87 Tubocoupe, Light Regatta Blue, All Options incl. Leather; 2.5" exaust, Dynamax super turbo mufflers w/3"chrome tips, MSD 6AL, Blaster2 Coil and wires, Homemade adjustable boost valve.
"The stage is set, the orchestra engaged.... it's now time to see if you can dance."

There is a TPS gasket that has the approximate form of the TPS. The little seal that fits over the throttle shaft is something seperate. If you can't find one make it out of ceral box cardboard.

I've made TPS gaskets out of McDonald's french fry boxes before. I doubt if using your old gasket is the problem.
From how you describe your BCS being bypassed and how your turbo vacuum lines are hooked up, it sounds like you have your hooked up like I have mine. No boost control valve, just vacuum port to vacuum port with a hose. I get 17psi (at least that's what the gauge says) all the time in every gear after I hit about 2700 rpm. Some people say that the factory boost gauge isn't very accurate when you run higher boosts. Maybe stick another gauge on there and see what kind of psi you get.