Author Topic: No boost until higher rpm, whats wrong? (Read 5320 times)

rabbit GTI/GTD · « **on:** April 05, 2008, 04:16:11 pm »

Hey,
I have 1998 Jetta TDI, it has no power(not producing boost) until about 3000 rpm. What would the cause be?? Wastegate sticking, or has someone ran into this before and its a simple solution?. Oh, and the odd time it doesn't produce boost at all, shut the key off and back on, and it will produce boost again, thanks for any help

jtanguay · « **Reply #1 on:** April 05, 2008, 04:24:19 pm »

does that engine have an electronically controlled wastegate???

maybe open the hood and check near the turbo for any wires. remove them?? you'll probably get a CEL though... just for troubleshooting purposes! :lol: :wink:

rabbit GTI/GTD · « **Reply #2 on:** April 07, 2008, 08:41:33 pm »

not sure, but it may be electronic, i'll have to check, under acceleration i hear a relay click, so that could be it functioning. If it's electronic theres a servo that controls the wastegate??

hendomatic · « **Reply #3 on:** April 08, 2008, 09:25:39 am »

Quote from: "rabbit GTI/GTD"

Hey,
I have 1998 Jetta TDI, it has no power(not producing boost) until about 3000 rpm. What would the cause be?? Wastegate sticking, or has someone ran into this before and its a simple solution?. Oh, and the odd time it doesn't produce boost at all, shut the key off and back on, and it will produce boost again, thanks for any help

Hi,

Might as well try to help on my first post to this list.

The 98 jetta TDI(I have one too), has an ECU controlled waste gate. There is a valve on the passenger wheel well called an N75 valve. This valve is modulated to allow boost to open the wastegate when the ECU thinks the boost is too high.

I'm pretty sure the wastegate is normally closed so perhaps your wastegate or actutator is likely stuck open.

If you have access to low pressure air or a pump, you can test the action of the acutator by applying it to the wastegate and if everything is working properly, you should be able to see the acutator move the wastegate at about 5psi. If it doesnt move at all at 15 psi, either the acutator is shot or the wastegate is stuck.

Thats where I would start.

The second place to look would be to check the N75 valve for proper operation. applying 12 volts to the valve should produce an audible click. If it doesnt, check the resistance. It should not be "open".

If its not "open" and there is no sound, the valve may be stuck in the "open wastegate" position, causing your no/low boost situation.

The TDI will produce some boost at high throttle loads even when the wastegate is open.

Hope this gets you started in the right direction.

Dennis