Quick question since I can't seem to find the answer.

2003 Jetta TDI.

Testing vacuum system at idle.

N75 has 25" Hg to top hose nipple when engine is idling (connected MityVac).

My question is "If I remove the vacuum hose to the VNT actuator at engine idle and attach my MityVac to its N75 nipple, what should I read? Vacuum? Atmospheric?"

Thanks!

You should have a strong vacuum, 20 inHg or so

Fix_Until_Broke said:

You should have a strong vacuum, 20 inHg or so

Click to expand...

Thanks, at idle, I have no vacuum on that port. Maybe that is the cause of the strange hesitation and black smoke at ~2,000 rpm under a slight load.

All depends on your tune...

I suppose someone could tune it to be at zero vacuum to the actuator at idle, but OEM, Rocketchip, Malone and TDTuning all go to "full" vacuum at idle.

Maybe swap your N75 with N18 and see if you've got a bad N75 valve.

Fix_Until_Broke said:

All depends on your tune...

I suppose someone could tune it to be at zero vacuum to the actuator at idle, but OEM, Rocketchip, Malone and TDTuning all go to "full" vacuum at idle.

Maybe swap your N75 with N18 and see if you've got a bad N75 valve.

Click to expand...

Thanks,

Kerma 150 HP tune, VNT17 Turbo, Bosio nozzles. Yes, I'll swap the two valves tomorrow.