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What's wrong with my engine?

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bijs   
Thu Feb 13 2025, 04:40pm
Joined: Apr 14 2019
Member No: #3890
Location: Oss
My 2.7 hdi from 2007 no longer runs.
Drove somewhere two weeks ago without any problems, after an hour when I was ready to go back, the car wouldn't start.
It started with a lot of effort and it is possible to keep it running, but when the accelerator is released it slowly turns off.
Brought to the garage by towing service.
Read the codes and it only shows that the air measurement shows a lot of difference and that the turbo pressure is too low.
Pressure sensor cleaned: okay
By playing with the accelerator it is possible to run the engine at 1500 rpm and then it seems to be running on 6 cylinders, but when you release the accelerator the engine also slowly stops running (first on 3 cylinders?) and then turns off. no strange engine noises during testing.
EGR valves disconnected, no effect, they also shift well.
While running, the front air mass meter appears to indicate 300 mg/sl and the rear 800 mg/sl.
Removed the air mass meters from the hose and it turns out that the rear turbo sucks air into the intake and that air blows from the intake hose of the front turbo.
Both turbo adjustments work and go up and down well
Front turbo disassembled and inspected. Turbo and adjustment are all okay.
What else can we do or does anyone have an idea where to look?


FYI, replaced oil/filter and fuel filter 4 weeks ago.
MGmike   
Thu Feb 13 2025, 10:44pm

Joined: May 21 2017
Member No: #3151
Location: South Queensferry
Hmm, this is an interesting one

The obvious place to look is the front turbo. If air is blowing back to the filter housing the turbo can't be spinning. Although you say the turbo adjustment works, have you been able to check it's operation while the engine is running?

If the actuator (adjuster) is working correctly it would suggest the turbo main shaft may have snapped or one of the turbine wheels has detached from the shaft or, more likely given the engine looses output from a number of cylinders, it could be due to a lack of exhaust gas flow which will also result in no intake air flow. This could be caused by a plugged pre-cat or damaged exhaust pipe from the front turbo/pre-cat to the CAT/DPF unit.

I would start by disconnecting the pre-cat at the front turbo to see if it allows the turbo to spin. Then remove the Y pipe where the turbo outputs combine before entering the intercooler. This will allow you to check the output of each turbo and should allow you a view of one side (the air side) of the front turbine.

Please keep us posted on progress.
 

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