Hi Guys,

I have a Octavia MK I VRS (AUM 1.8T, 150 BHP). The only aftermarket fitment is a K&N (not an SRF, so the factory airbox is gone). The car has run about 45,000 miles.

Here's the problem. When cold, the engine seems fine. The turbo gives boost and the car pulls cleanly till 6000 RPM, as it should. However, once the engine warms up, and the temperature gauge reaches the half mark, the boost tapers off, and at wide open throttle, the boost abruptly cuts off at about 4750 RPM, and the car simply refuses to rev normally; it's as though the engine is being strangled for air post 4750 RPM, and there's loss of power. At operating temperature, the boost comes in normally at 2000 RPM, till 4500; after that, there's an abrupt cut-off, and it feels like the fuel & air have been restricted.

I've tested this multiple times, and the problem is only when the engine is warmed up and upto operating temperature. When cold, the engine revs freely & the boost is felt right uptil 6000 RPM.

Any ideas/suggestions/thoughts?

Thanks for all the inputs in advance..

Coolent temp sensor? No warning lights or owt?

Coolant temp sensor.

There are no checklights coming up. Haven't tried a vag-com yet. Wouldn't a coolant sensor issue throw up a CEL? Also, if the sensor were faulty, shouldn't the temp gauge go haywire?

Am trying to think of all possibilities...experts, kindly guide..

There are no checklights coming up. Haven't tried a vag-com yet. Wouldn't a coolant sensor issue throw up a CEL? Also, if the sensor were faulty, shouldn't the temp gauge go haywire?

Am trying to think of all possibilities...experts, kindly guide..

Sensor is a 2 way job, one for the dash gauge and one for the ecu, it could be that your ecu side is knackered

Temp sender doesn't put lights on most of the time

Thanks, guys...shall check it out and update....

There's another thing that I forgot to add; the airbag check light has also popped up, although no accidents have happened. Do you think the airbag check light would tell the ECU to limit boost/fuel/ignition tables?

Hey guys, just checked on a friend's VAGCOM. The error codes thrown up are: U48023, & 65535. These seem to be airbag control module errors. Any thoughts on whether these would be the problem areas causing the boost cut-off & how to rectify this? Help....