You shouldn't need to do that. The car will start and run with the vacuum off. It just won't run as well.maybe I can tee in my hand-pump / gauge, and then start the engine
Thats insanee*clipse said:You shouldn't need to do that. The car will start and run with the vacuum off. It just won't run as well.
To understand the VNT, here's a video:
Note that when a vacuum line is connected to the top connector (the one on the far right in this video) the actuator will pull on the VNT mechanism. As the actuator pulls (more vacuum) the vanes "close" thus speeding up the turbine.
This is shown in this video, with the exhaust gasses animated:
As the motor speeds up (more exhaust gasses) the ECU adjusts the N75 duty cycle to release the actuator and open the vanes.
If your actuator was stuck in the released position (as mine was) you basically won't get boost until later in the RPM range.
That sounds easy, but ... (silly question) where is the Rigid Brake Booster Vacuum Line ???1. disconnect the 'vac' hose. Connect a mighty vac to the hose. Start the car. You should get >25 inHg vacuum.
2. connect a vacuum hose directly from the rigid brake booster vacuum line to the 'vac' port on the N75. You'll get an EGR code, but your turbo oughta work great.
If 1 doesn't occur, of if 2 fixes the problem; find the vacuum leak. Vacuum is drawn from the rigid line. The line splits twice such that you have 4 unregulated vac lines. One to the N18 (EGR), one to the N75 (turbo), one to the vacuum reservoir and one to the N239 (anti-shudder valve).
My setup is completely different, with the turbo and motor rotated, so "up" and "down", "front" and "back" get confusing. How about "toward the stop screw" and away from the stop screw"?I might have mixed this up (again); I think when my engine is off, the linkage is "up", right? Spring pressure forces it up? Applied vacuum makes it pull "down"? I usually (now about 2/3 of the time) get that brief overboost, when starting the engine ... more often when warm-started (cold start usually no initial overboost). If my problem was, poorly regulated vacuum (meaning, N75 doesn't cut off the vacuum properly, as I suspected) then I think I got this right (i.e. when I start the engine, it pulls downward too much on the linkage).
You took your car to the dealer and they replaced a few things, then you decided to take over. We don't know all of what was done to the car so it's difficult to tell if you checked all that is needed.PicknCrew said:Replacing parts and cleaning things still didn't resolve my limp mode problems. After much time and expense I resolved my intermittent limp mode symptoms with a google search and spending $50 on a boost controller (check valve). Inherent design flaw in these TDI engines in my opinion.