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Low air flow problem
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mg407   
Mon Apr 24 2023, 08:42am
Joined: May 08 2022
Member No: #5016
Location: Putney
re - Click Here -

Sorry to bring this dead thread back to life, but I have exactly the same issue re low rear MAF reading but have both EGR's blocked off, so it sort of does not matter if they work or not as the "exhaust" holes to the inlet manifold are blocked off .

This suggests I may have a opening between the turbo and the MAF / air box, which is sucking in air after thye MAF so that the rear MAF reads low.

Ive looked hard and low and can't seem to see any holes, but may try and pressurize it somehow and see if I can spot a opening (maybe smoke or fog machine)

I also understand that both turbos feed into the same inlet manifold.

Any other suggestions ?
MGmike   
Mon Apr 24 2023, 04:12pm
Joined: May 21 2017
Member No: #3151
Location: South Queensferry
 A smoke test would be a good place to start.
If there are no leaks from the MAF to the input of the inter cooler (where the two turbos combine at the front of the engine), you might be looking at a failed turbo actuator which maybe causing a reduction in airflow.

Good luck
mg407   
Mon Apr 24 2023, 08:51pm
Joined: May 08 2022
Member No: #5016
Location: Putney
 Thanks

Can I assume at idle the turbo's are not spinning / there is no exhaust pressure but the air flow is still low and so the actuators don't matter ?

Does Diag show the position of the actuators eg if the rear is stuck ?

The car does okay otherwise and I seem to have reasonable boost.

Looking at some pictures of a engine out of the car, I'm now wondering if there is a disconnected pipe (or something allowing more air to come in after the MAF)

mg407   
Tue Apr 25 2023, 08:50pm
Joined: May 08 2022
Member No: #5016
Location: Putney
 I tried the smoke test into the rear air intake pipe and only could see smoke coming out of the rear turbo outlet (with the steel pipe removed).

I tried to get to the inlet pipe #2 between the rear air intake pipe to the rear turbo and the oil seperator breather box #3 (4R8Q-6A785-AE) from the top of the engine but failed even after removing the steel pipe as there is no room to stick your hand down past the firewall etc. The diesel filter is also in the way as is the starter motor.

So got under the car to see if I can get to the pipe from underneath but again no room to put your hand up due to exhaust pipework.

Any tips on you can get to the oil seperator breather box pipes ?



mg407   
Thu Apr 27 2023, 01:13am
Joined: May 08 2022
Member No: #5016
Location: Putney
 I had a look thru the technical documents and it seems the diesel fuel filter assembly has to come off at a minimum, based on reading the starter motor change documents (eg the oil seperator is sort of in the the same location) - - Click Here -

I also found some turbo boost data (2500 rpm 0.3 +/- 0.05 bar and full rpm 1.3 +/- 0.4 bar) so will run the car and see what mine does - I assume this is a average reading for both turbo's - see - Click Here -
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