The Big wheel
New member
Hello, I am new to this site and to the tdi world......but not to the diesel world. I own a 1998 vw jetta tdi with the ahu engine. I suspect that I have a bad n75 valve stuck in the gimme less boost condition. While in a hard pull at random times the engine will go into limp mode and sometimes give a p1550 code. I have checked for boost leaks vacuum leaks and found none. I have even checked the line inside the ecu. I have checked the intake for clogging and it is clean. I have checked power to the n75 valve and the resistance reading of the n75 valve and both are OK. With the n75 removed and on the bench if I apply shop air to the charge air port on the n75 valve (red house port) I have same amount of shop air comming out of the waste gate port or (blue hose port). These ports should not be connected to each other until there is power sent to the n75 valve correct? I think this is causing me too have low boost pressure during a hard pull causing the code and the limp mode. Is this possible? If anyone could give me some help it would be great. I do have a stage 1 malone tune with egr delete and a south bend clutch. Thanks