Diagnosing Hesitating/Misfiring X35i with No Codes

[ClutchKickChris]

Originally Posted by SB1120

I remember something similar. I think it was the electronic bypass valve on the compressor. It might be worth removing to inspect..? I’ll attach a pic of one in a Passat I had. No code but I read it was common, removed it and sure enough the diaphragm was blown. Not sure if they use this same design on our Borgs.

If you can hear boost bypass after a part-throttle mid-range pull, its probably ok?

Ever replaced the valve cover? And also related to that, the short pcv pipe between the turbo inlet pipe and valve cover if cracked could be an air leak. In terms of air leaks: charge pipe to inter cooler seals, crack in charge pipe(s) after intercooler, and there’s a seal between the intake manifold and DME. That one is less likely but if oil vapor has attacked it, it could be shot.

Yes for sure I can hear bypass when letting off throttle at heavy load.

I did recently replace the valve cover AND short PCV pipe with OEM, VC was slightly leaking oil, was hoping maybe it'd fix any air leaks too if they existed.

As for the turbo diverter valve, the feeling of this stutter/hesitation is very sharp, like a misfire feeling. I think turbo pressure issues would be more gradual, like a sine wave sweep vs a sawtooth (what I feel).

[SB1120]

Originally Posted by ClutchKickChris

Yes for sure I can hear bypass when letting off throttle at heavy load.

I did recently replace the valve cover AND short PCV pipe with OEM, VC was slightly leaking oil, was hoping maybe it'd fix any air leaks too if they existed.

As for the turbo diverter valve, the feeling of this stutter/hesitation is very sharp, like a misfire feeling. I think turbo pressure issues would be more gradual, like a sine wave sweep vs a sawtooth (what I feel).

How does your high pressure fuel reading look during these events?