Psych0matt Posted September 18, 2008 Report Share Posted September 18, 2008 I replaced the modulator on the TGP to see if that would help my non-shifting problem, and really it seemed to make things worse. My boost guage used to read a little bit below zero on idle, but not bad, and since the modulator change, it sits about 3/4 down below 0. Now, is this adjustable, because I'm pretty sure this is where all my problems are stemming from (lack of vacuum, not necessarily the modulator for sure). Up until I started working on the TGP I had no vac trans experience at all, and so far I haven't been a fan of vacuum problems ever I wanted to at least get it drivable for a while before I have time for the 5 speed swap and wanted some suggestions/ideas Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted September 18, 2008 Report Share Posted September 18, 2008 When my TGP is at idle, the boost gauge usually sits about 3/4 of the way down from 0. That is normal. During normal driving, it should stay below zero also, but above where it sits at idle. I dunno if that helps any, hopefully it did Quote Link to comment Share on other sites More sharing options...
Psych0matt Posted September 18, 2008 Author Report Share Posted September 18, 2008 hmmm, under boost it only goes up to maybe halfway below zero. I guess it's just odd that it used to read much higher. Maybe I don't in fact have a vacuum issue at all oh well, the 5 speed is coming soon enough, just wanted to be able to drive it a bit until then Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted September 18, 2008 Report Share Posted September 18, 2008 On mine the gauge sits like this: idle= 3/4 of the way down in the vacuum side. cruising at 55MPH= 1/4 of the way in the vac side. 1/2 throttle=0 Full throttle on stock chip=3/4 of the way up in boost Full throttle on Hot Tune= Top of booost gauge. I think you may have a vacuum leak somewhere. The vac line popped off the back of my intake plenum once and the gauge just sat toward the bottom of the vac side and barely moved. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted September 19, 2008 Report Share Posted September 19, 2008 Matt, I had a similar issue once. It ended up being a small hole in the vacuum line from the modulator to the TB. Took a while to find it, but I ended up replacing the whole line. Check the other lines around the TB, too. Especially the hard plastic ones. The older they get the more brittle they become and can break with little effort. Quote Link to comment Share on other sites More sharing options...
IRONDOG442 Posted September 19, 2008 Report Share Posted September 19, 2008 Since no one has answered his question I will. It's pretty bad when the forum jag off has to answer questrions on here, that is not what I signed up for!!! Matt, yes they make an adjustable vaccum modulator. But I am not sure if you dont already have one. To find out look down the nipple where the vacuum line actually plugs into on the outside of it and if you see a small adjustable set screw in there that a flat blade jewelers screw driver will fit into. If there is one there, your modulator is adjustable. Usually they can only be adjusted about plus or minus 5 mph. If I recall correctly turning the set screw right will pro long your shift points and turning it left will hasten your shift points. Good Luck !!! Quote Link to comment Share on other sites More sharing options...
Hairdo12 Posted September 19, 2008 Report Share Posted September 19, 2008 Did you verify the O-ring between the modulator and the transmission is still there and not damaged? Or that the old O-ring wasnt left behind and isnt causing problems? Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted September 20, 2008 Report Share Posted September 20, 2008 Since no one has answered his question I will. It's pretty bad when the forum jag off has to answer questrions on here, that is not what I signed up for!!! Matt, yes they make an adjustable vaccum modulator. But I am not sure if you dont already have one. To find out look down the nipple where the vacuum line actually plugs into on the outside of it and if you see a small adjustable set screw in there that a flat blade jewelers screw driver will fit into. If there is one there, your modulator is adjustable. Usually they can only be adjusted about plus or minus 5 mph. If I recall correctly turning the set screw right will pro long your shift points and turning it left will hasten your shift points. Good Luck !!! It's not really shift points so much as "shift feel". Maybe it bumps shift points a little, if it does it's not noticeable. Turning it in makes it feel firmer, and out makes it feel sloppier. Usually start with 1/4 to 1/2 turn increments to see how you trans react and how you like it. Shift points are more easily controlled via the TV cable. Hairdo's point is a valid one also. I know I've done that before. Quote Link to comment Share on other sites More sharing options...
1990lumina Posted September 20, 2008 Report Share Posted September 20, 2008 Do the boosted cars have a vacuum pump? I always thought boosted cars have very minimal vacuum. My Millenia had a big vacuum pump for instance, although that car had a shit ton of valves and circuits that relied on a constant vacuum source Quote Link to comment Share on other sites More sharing options...
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