Jon37

Low inlet manifold pressure.

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Hi. I’m looking for a little bit of help. I have a 2006 focus 1.6tdci that would seem to have a bit of a turbo problem. The car lacks any kind of performance and can’t seem to hold its speed when going uphill. I have checked for fault codes on the OBD but there aren’t any. When I look at the live sensor data the MAP is only showing  a maximum of 104kpa. It holds at a steady 99kpa while idling. 

The are no obvious turbo leaks. And the turbo does appear to be spinning. 

I have also noted that the data for the common rail pressure looks a little off. As the car accelerates the pressure increases to start with but decreases rapidly as the car starts to struggle to accelerate. 

I’m left wondering if it’s a fuel supply issue holding the turbo back or turbo issue where the ecu is reducing the fuel pressure to compensate. Any help would be gratefully   received.

There is no black smoke and the car seem to be running fine in every other way. No misfires and smooth idle  

 

 

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2 hours ago, Jon37 said:

I’m left wondering if it’s a fuel supply issue holding the turbo back or turbo issue where the ecu is reducing the fuel pressure to compensate.

I am surprised there are no codes. On my car (1.8), the P0299 (boost pressure DTC) did not register on a generic OBD2 scanner, but it did show up on Forscan. It also did put the engine system lamp on. That fault turned out to be just a broken little pipe to the pressure sensor.

I would guess the ECU is limiting fuel by cutting the rail pressure when it detects insufficient air flow or pressure. 104kPa is a very low boost pressure, the air flow in a diesel depends on rpm much more than on fuel rate, so the turbo should ramp up more than that even with a fuel problem.

Saying that, I would still change the fuel filter unless you know its a good'un, it can have odd effects.

After that I would suspect the turbo vacuum solenoid, or its pipework.

 

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