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View Full Version : Good vac, No boost



jayd21
09-01-2004, 07:49 PM
I can't get any boost.The vacume presure will get to zero but I only see boost for like 30 seconds after it's been started after sitting for a little bit. Then once she's warm I get like a pound or to. Help me I miss my boost.

Bacondoggy
09-01-2004, 08:00 PM
this is REALLY stupid I know, but are you feeling an extreme loss in accelleration? if not, your boost gauge wire (pressure indicator) could either be leaking or could have came off the nipple. it is located on the rear of the plentnum where the LOWER ic tube attaches to (like under the drivers side wiper). you may have to take the wipers and the black plastic off to get enough clearance to get to it...

rlong
09-01-2004, 11:02 PM
if its older model there is a seloniod mine did that i just bypassed the seloniod and hooked the vacuum hoses together its near the drivers side hood hinge or boost bypass isnt working

darkstar_one
09-01-2004, 11:30 PM
hey, is ur air bypass valve opened? does it close when u smash on the pedal? if not then i think this can be ur problemo. just a though

edspringer
09-02-2004, 09:16 AM
My rubber boots on my 90 XR7 blower bypass valve vacuum line were old and starting to crack. I got new boots and put them on the existing plastic vacuum line. When I fired her up I had great vacuum but no boost. In fact when I accelerated the engine it sounded like someone had thrown a hand full of ball bearings into my blower. I noticed that when I moved the accelerator, the bypass valve did not move like it did before. Further investigation revealed that when I put the rubber boots on the plastic line I pushed them on to far, effectively, plugging the line.

Ed Springer

90 Black XR7 5-speed: 70mm TB, Fresh Air Intake, '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, 190 l/h Fuel Pump, 36# Injectors, Headers, Magnaflow Muffler (no cats) with stock resoantors, 3:27 Gears, Ripper Shifter, 73 CL MAF, Magnacore Wires, NGK Iridium Plugs and Rear Spring Air Bags.

94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, 190 l/h Fuel Pump, 38# Injectors, Headers, Raven Muffler (no cats) with stock resoantors, 3:73 Gears, 73 CL MAF, Magnacore Wires, NGK Iridium Plugs, TRANSGO Shift Kit, ProTorque 2500 Stall TC, Haydon Auxiliary Transmission Cooler, Tokico Struts & Shocks, American Racing 17 Sniper Wheels, Michelin Pilot Sport A/S Tires and 235 RWHP with 315 Lbs.Ft. Torque.

jayd21
09-02-2004, 06:45 PM
I can't get any boost.The vacume presure will get to zero but I only see boost for like 30 seconds after it's been started after sitting for a little bit. Then once she's warm I get like a pound or to. Help me I miss my boost.
I will get boost for lke 40 seconds when I start it But then nothing. It's like there is a wall at 0 on the vac/boost guage. I noticed that the by pass will open but its real slow to shut when i shut the car off, Im a rookie at this so any suggestions or things I could do to find out whats wrong would be greatly apreciated.

jayd21
09-02-2004, 07:57 PM
I can't get any boost.The vacume presure will get to zero but I only see boost for like 30 seconds after it's been started after sitting for a little bit. Then once she's warm I get like a pound or to. Help me I miss my boost.
I took the vacume line of the by pass acumulator so the by pass valve stayed closed and i got full boost no problem. so does this mean the acumulator is bad? And what damage will i do if the valve just stayed closed.

darkstar_one
09-02-2004, 08:20 PM
well... i dont think there is nothing wrong with having it just close all the time, but i would replace it, i think it will affect ur fuel economy since ur gonna be making boost all the time u step on it, so i would check it and throw some WD in it or something, work on it.