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Dead spot below 1500 rpm

9K views 6 replies 2 participants last post by  TonyMoneo 
#1 ·
Hello my fellow tractor drivers

I have an issue with my B7 2.0 TDI. In South Africa the Le Mans was a special edition of the 2.0 TDI engines (125 kW) with the BRD engine code. I bought the car second hand, and thought that the low power below 1500 rpm was just a lag issue. I browsed the forum and it seemed like the Le Mans was known for its terrible lag. So I just accepted it.

In an attempt to reduce what I thought was just turbo lag, I had the DPF removed, did the downpipe and got a software upgrade. It did improve high end power but the "lag" was still terrible.

I had the turbo, clutch and flywheel replaced over the weekend. The technician that worked on my car also drives a Le Mans. After seeing what my car should be like I am quite upset. Especially keeping in mind that his Le Mans didn't have any of the upgrades that I have done on my car - and he doesn't have the same issue at low rpm.

It is definitely not turbo lag, there must be some other issue and the best that I can describe it is a dead spot. There is absolutely NO power until you go beyond 1500 rpm.

We had the following checked in an attempt to find the culprit for the dead spot:

*Overhaul the fuel pump
*Check pulley allignment
*Replace N75 solenoid
*Thoroughly test the injectors
*Replace the boost pressure sensor
*Check for vacuum leaks
*VNT actuator is brand new so the turbo spools at low rpm

When the boost pressure sensor is removed completely, the low end power seems to be fine (but you get a significant amount of overfueling).

This is as far as my fault-finding ability goes. Any one with similar experiences or advise will be much appreciated.

Thanks!
 
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#4 ·
My thinking is the wrong actuator setting would or could act similar to a boost or vac leak. Could a dodgy maf cause this too? I've experienced some weird issues caused by a maf, it only ever seems to show a fault if there's a problem with the power but it's rarely the power supply that's at fault.
I suppose one way to do a quick check would be to disconnect the maf and test drive, see if the lag improves.
 
#7 ·
The problem has been resolved :) :) :)

So in short what happened was the following:
The shaft of the oil pump got worn out pretty bad. This lead to an oil pump failure which gave a low oil pressure warning on the dash. As a result, no oil made its way to the turbo causing it to cease. The exhaust gas temp (EGT) sensor is situated right next to the turbo. I'm guessing things got quite hot when the turbo wasn't cooled down, but something caused the EGT sensor to fail. As a protective measure the sensor assumes the most conservative reading to prevent further damage to the vehicle. Some investigating on VCDS showed an EGT of 1000°C!! It was difficult to identify the faulty sensor because no errors were logged. After replacing the sensor the car pulled like a dream again ;)
 
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