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Hey I have a 1990 mkIII with the 7mgte and I'm currently dealing with a problem of boost loss at normal coolant temps. So when I cold start it (I let it idle like 1-3min before moving it because its cold outside right now) I get about 10-12 lbs of boost but only about -15-18 vacuum out of it but as soon as I see the temp gauge move I notice that I'm only full pulling about 5-6 pounds but I get about -21 vacuum at idle. Kinda at a loss as towards whats going on. So everyone knows what has been done its a stock turbo 124k with stock motor. Catless downpipes with open waste gate dump tube, cold air intake, Gates Blue timing belt with all front seals and the crankshaft timing belt pulley replaced.(found missing outer piece) I changed the exhaust manifold gasket, turbo gaskets and all the head studs for the exhaust manifold, did a set of plugs and wires with valve cover gaskets and both knock sensors due to having a cel for them. I also have the intake pipes under the hood changed because the factory one was in the way of the strut tower bar and it hit the hood but I have switched it back and I still see the same problem. Everything look good when I had the turbo out so I put it back in but I really am just not sure whats up. My next upgrade was going to be injectors,fpr,and boost controller to try and get a little more power out of it but now this problems has me worried to try it. Just unsure of it the vacuum pressures being off that much its a sign of a head gasket or piston ring problem. I do notice a little blue smoke if I sit at a traffic light then try to pull away but a friend told me that it just the valve guide seals because its not smoking all the time. I do have a brand new cylinder head and head gasket set for it but I have been saving money because I want to get the bottom end rebuilt and upgraded and I know when to have the block decked that plate in the front need to be done to with it. Hopefully someone else had this problem and could help me out. Thanks
 

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Hey I have a 1990 mkIII with the 7mgte and I'm currently dealing with a problem of boost loss at normal coolant temps. So when I cold start it (I let it idle like 1-3min before moving it because its cold outside right now) I get about 10-12 lbs of boost but only about -15-18 vacuum out of it but as soon as I see the temp gauge move I notice that I'm only full pulling about 5-6 pounds but I get about -21 vacuum at idle. Kinda at a loss as towards whats going on. So everyone knows what has been done its a stock turbo 124k with stock motor. Catless downpipes with open waste gate dump tube, cold air intake, Gates Blue timing belt with all front seals and the crankshaft timing belt pulley replaced.(found missing outer piece) I changed the exhaust manifold gasket, turbo gaskets and all the head studs for the exhaust manifold, did a set of plugs and wires with valve cover gaskets and both knock sensors due to having a cel for them. I also have the intake pipes under the hood changed because the factory one was in the way of the strut tower bar and it hit the hood but I have switched it back and I still see the same problem. Everything look good when I had the turbo out so I put it back in but I really am just not sure whats up. My next upgrade was going to be injectors,fpr,and boost controller to try and get a little more power out of it but now this problems has me worried to try it. Just unsure of it the vacuum pressures being off that much its a sign of a head gasket or piston ring problem. I do notice a little blue smoke if I sit at a traffic light then try to pull away but a friend told me that it just the valve guide seals because its not smoking all the time. I do have a brand new cylinder head and head gasket set for it but I have been saving money because I want to get the bottom end rebuilt and upgraded and I know when to have the block decked that plate in the front need to be done to with it. Hopefully someone else had this problem and could help me out. Thanks
It's kind of hard to follow what you're saying here. While at idle you will get zero boost and will see negative vacuum no matter the temp outside or engine temp. Only when the vacuum moves into the positive will you see a positive rise in boost all predicated on an increase in rpm. If you are not getting boost then check all vacuum lines. If they are good and you still fail to get boost check the gate diaphragm. If thats good and you fail get get boost check the blow off valve for vacuum leaks. Always check for major shaft play on the turbo as that could contribute as well. You may want to restructure your question in the form of multiple questions that are a little bit clearer.

GE
 

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Discussion Starter #4
It's kind of hard to follow what you're saying here. While at idle you will get zero boost and will see negative vacuum no matter the temp outside or engine temp. Only when the vacuum moves into the positive will you see a positive rise in boost all predicated on an increase in rpm. If you are not getting boost then check all vacuum lines. If they are good and you still fail to get boost check the gate diaphragm. If thats good and you fail get get boost check the blow off valve for vacuum leaks. Always check for major shaft play on the turbo as that could contribute as well. You may want to restructure your question in the form of multiple questions that are a little bit clearer.

GE
So to make it easier to understand before the temp gauge moves I get 12lbs of boost at WOT I know not supposed to do it but that is how I found the problem and once the temp gauge start to go up its like the car cuts the boost down to 5-6 lbs at WOT and I can feel the power different. The vacuum is also less when its cold and more when its warm. Theres no boost cut no black smoke but I can feel the power difference once it gets warm. I will leave it at this when its cold I can smoke my Buddys 350z but once it get warm he leaves me standing still.
 
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