Looks it, which I reckon leads you back to the dump valve being the cause of the weird MAF readings on overrun.
I’m not sure that’s correct. If the wastegate was faulty you wouldn’t get an increase in flow through the MAF on your overrun.
If one of the dump valves is faulty the pressure on overrun has nowhere to go as the throttle is closed so it goes the wrong way through the MAF. By disconnecting the actuation of the wastegate you’re reducing the efficiency of the turbo and thereby reducing the pressure so it may not be flowing back through the MAF and causing the spike in MAF readings on overrun.
I’m not sure that explains your symptoms 100% either.
Glad the mystery is solved; sorry it's not a less expensive lesson...Well wasn't *that* fun.
I am now supremely confident we know what the issue is, simply because it is the most expensive thing it could possibly have been. (Sometimes it pays to fire the parts cannon, I guess!)
After much cursing, swearing and dropping of tools, 5 out of the 6 heatshield bolts came off. Not that it does much good because on bank 3 you *still* can't see the wategate actuator, or the diverter valve.
With some advice from the US, got into bank one, and lo! The wategate pivot into the manifold is worn. So that's a replacement tubo, thankyou very much indeed!.
Well it happens, One is on its way. I can probably claw back a lot of my costs on this bundle of laughs so all's well. Or will be well. Or might be I guess
C
That will have been the rattle then Chris ?
How many miles has she done ?
Good to hear you finally got to the buttom of the issueWell wasn't *that* fun.
I am now supremely confident we know what the issue is, simply because it is the most expensive thing it could possibly have been. (Sometimes it pays to fire the parts cannon, I guess!)
After much cursing, swearing and dropping of tools, 5 out of the 6 heatshield bolts came off. Not that it does much good because on bank 3 you *still* can't see the wategate actuator, or the diverter valve.
With some advice from the US, got into bank one, and lo! The wategate pivot into the manifold is worn. So that's a replacement tubo, thankyou very much indeed!.
Well it happens, One is on its way. I can probably claw back a lot of my costs on this bundle of laughs so all's well. Or will be well. Or might be I guess
C
Good to hear you finally got to the buttom of the issue![]()
Fingers crossed for you. Did you see if putting a vacuum on the wastegate affected the MAF readings?
Raw Vacuum | 740 | ||||
Solenoid Vacuum | 500 | ||||
Bank 1 Vacuum | Bank 2 Vacuum | MAF 1 | MAF 2 | ||
0 | 0 | 8 | 8 | ||
1 | 1 | 7 | 14 | ||
1 | 0 | 10 | 7 | ||
0 | 1 | 6 | 20 |