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Hi, I have noticed recently that the boost LED sometimes illuminates with reduced performance ( 1.3 bar limit ). Most of the time it happens when starting the engine and once the oil is warm if the engine is switched off and then back on the problem goes. If driving at a steady speed the red LED is always on, if I take the car out of gear and coast the LED goes out once the engine is at tickover then flashes 4 times then 2 then there is a gap before repeating. Any help to shed light on the problem will be greatly appreciated,

MIKE.
 

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Hi, I have noticed recently that the boost LED sometimes illuminates with reduced performance ( 1.3 bar limit ). Most of the time it happens when starting the engine and once the oil is warm if the engine is switched off and then back on the problem goes. If driving at a steady speed the red LED is always on, if I take the car out of gear and coast the LED goes out once the engine is at tickover then flashes 4 times then 2 then there is a gap before repeating. Any help to shed light on the problem will be greatly appreciated,

MIKE.
Good afternoon Mike,

As far as i know and i'm sure someone will correct me if i'm wrong but when this light illuminates it means that there is a problem with the turbo boost control circuitry and if i was you i would not drive it until this problem is fixed. If you continue to drive the car you risk damaging the engine!

I hope this helps
 

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Hi, I have noticed recently that the boost LED sometimes illuminates with reduced performance ( 1.3 bar limit ). Most of the time it happens when starting the engine and once the oil is warm if the engine is switched off and then back on the problem goes. If driving at a steady speed the red LED is always on, if I take the car out of gear and coast the LED goes out once the engine is at tickover then flashes 4 times then 2 then there is a gap before repeating. Any help to shed light on the problem will be greatly appreciated,

MIKE.
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4 2 tension/voltage on the throttle switch is to high - higher than 4,3V

readjust the potentiometer.

see here how to:
http://www.m5board.com/vbulletin/al...problems-high-rev-coughing-7.html#post1449706

or here
Tomba said:
2 TPS Adjustment
2.1 Throttle valve closed (igntion off / accelerator pedal not equipped)
2.2 Move the potentiometer to the left till it switches (click sound)
2.3 Tighten the bolts for the TPS slightly
2.4 Connect an Ohm meter to pin #1 & #3 of the TPS
2.5 Turn the ignition on, no running engine
2.6 Let someone else or use a stick to give full throttle
2.7 The measured value on the ohm meter must be 310 +/- 5 Ohm
2.8 If this value is shown, tighten the bolts.

If the value is not shown, use the following points

2.9 Unloosen the TPS bolts
2.10 Turn the TPS so, that it will indicate 310 +/- 5 Ohm.
2.11 Tighten the bolts of the TPS slightly
2.12 Give serval times full throttle to the accelerator pedal, the value must be the same all times (very important!)
2.13 Tighten the TPS
2.14 If the value 310 +/-5 Ohm aint showen the TPS has to be replaced
 

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Hi, thanks for the info, this is excellent stuff. Last year I adjusted this as per the above instruction due to the car coughing at high revs. I checked the TPS again today and got 312 Ohms at full throttle but tried again and settled on 311 Ohms. Since the problem is intermittent and usually happens only when its very cold i'm wondering if the cold is enough to alter the resistance of the circuit sufficiently to trigger the warning but clears when the car warms up. Maybe the potentiometer is faulty, today I could not get the LED to activate but I will keep checking.

Thanks again,

MIKE.
 

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Great info here! I also seem to remember a thread where someone put a BT engine into a touring body and had poor running issues - traced back to the boost control. I'll see if I can find it. IF the light flashes, there is an issue and the boost bleed won't work properly hence the reduced output - the wastegates are seeing all the boost and opening early. With the boost ECU working correctly, the boost is bled away from the wastegates so they open at a higher pressure. [That's my understanding at least].

Cheers,

Dave.
 
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