Loss of power & high idle BKD

[Tdi boy]

With today's heat in sydney 38 deg I had the aircon at max, slowed down at the lights to notice that the idol was just above 1000rpm, turned aircon off, changed gears, gave it a rev & no change in idol.
So as I was driving back towards the city down the freeway I thought that it could be the heat affecting a sensor or something. As i was going to overtake there was a massive loss of power, as if a cooler hose had blown.
The outside dash temperature reading had now gone from 38 to 26 ( big change in weather) & for some reason some power has come back,but idol is still high 900rpm.
The car has no DPF is revo tuned, has a provent & has only done 15000 original kms.

This is worrying any suggestions?

[Tdi boy]

Well have just let the car sit for while, & went for another drive, idle still sitting at 900rpm & have power back but it feels like its lost a lot of low down torque, I was reading up on VNT vanes failing.
Maybe the cause.

[gldgti]

I would be trying to get some boost data. I'm not entirely convinced about the revo tunes personally, could be anything. IME, a stock TDI can have pretty significant boost spikes, and a tuned one can have even worse boost spikes. Perhaps you've had a boost leak or something..... do a VCDS scan if you can find someone close to do it for you.

I wouldnt jump to conclusions too early about turbo failure, could be many things before that. The weirdest thing is the idle being different.

Could be the VNT actuator, a mate of mine had one fail on his golf 6 recently. Little diaphragm inside the actuator had cracked and wasnt holding vaccum any more - means it wont spool up fast enough.

[Tdi boy]

Maybe a leak that's why the idles gone up, I'm going to get it scanned today

[gldgti]

Maybe a leak that's why the idles gone up, I'm going to get it scanned today

A leak wont change the idle - remember diesels air/fuel ratio doesnt affect idle speed.

One thing to check though is that the vent line that runs to the side of the airbox is clear - if this is blocked or kinked the VNT actuator wont work properly either.

[Tdi boy]

Got the car scanned today, with no error codes, so I don't know what the problem is???
It's lost a lot of torque especially when kicking back in 6th at about 70 & I can just feel overall power is down. Also idle is still fluctuating between 800-900.
I disconnected the provent & no difference there, oil is leaking from the drivers side cooler hose.
Otherwise the car is like new I just don't understand why the idle is up & torque is down surely the actuator & turbo aren't faulty this early.

[buzuki]

low battery voltage will make the engine ECU increase revs to force the alternator to charge harder.

low voltage can also lead to running issues.

Id just quickly check charging voltage

[Tdi boy]

[Greg Roles]

Is it a genuine Provent, or did you buy a Chip Tuning one? They are China copies that cause all manner of problems like this as they leak air back into the PCV system and mess up idle and fueling, I get a call about this almost daily.

Aydan is right in checking the return line from the VNT diaphragm isn't blocked, this happened on mine and it behaved VERY oddly.

A low battery and a diesel won't start, you need a perfect charge to crank the bloody things, they show up a failing battery well ahead of time.

The only way to properly diagnose is return tune to stock, and go from there.

[Tdi boy]

I've also noticed the DSG doesn't change down as much as it used to, it seems to hold taller gears at lower revs.