850 Turbo Zero Boost

[loosenut]

smoke test yet?
i had a boost issue and found a leak right around my BCV near the throttle. made a biiggg differance

[Nevada1906]

loosenut,

No, I haven't done a smoke test, but that's up next.

I installed the new MAC solenoid today. The setup that mimics the factory routing seems to be Port 1: Intake duct, Port 2: Wastegate and Port 3: Compressor. I can blow air through Port 3 and have it exit Port 2 - and vice versa - just like the factory BCS, so that tells me that this particular routing is correct.

I figure that even if the BCS was still good, it was also factory (240,000+ miles), so a new part removes that problem from the list of possibilities.

That wasn't my main problem, though. The car is still stumbling and bucking in Drive at low RPM and wants to stall out upon stopping.

The turbo is still not producing ANY boost, and the car runs rough enough that I don't want to even TRY to drive it long enough for it to throw a code - which it's not doing right now.

Well, off to the store for a cigar...

[Nevada1906]

Engine still runs with the MAF unplugged.

I think I just found the problem.

[loosenut]

@tryingbe still have the turbo for sale?

[abscate]

Engine still runs with the MAF unplugged.

I think I just found the problem.

The engine will run fine with the MAF unplugged, a bit rich, but a lot of people won't even notice the difference. Unplugging the MAF is an inconclusive test for pretty much any component.

[Nevada1906]

Problem solved!

Combine a very dirty MAF with a turbo bypass valve that won't hold vacuum and you get a week of diagnostic fun!

I absolutely hosed the MAF element and electrical connector with MAF cleaner and reassembled it.

Idle's smooth and strong, car accelerates normally and I've got a new diaphragm on order.

Everyone, thanks for all your help.