a3 8L 1.9tdi quattro boost problem...

davedoubledecks

Registered User
Joined
Feb 24, 2014
Messages
52
Reaction score
2
Points
8
Location
cheshire
don't know if anyone has any ideas...I was travelling down to wales on fri afternoon and I took a detour to collect something which took me on some steep remote lanes in the hills, the car is remapped to 170bhp and was on boost for most of the climbs, not flat out but pulling hard when all of a sudden the car loses boost altogether and appears to be in limp mode but not showing any faults on the dash....the car wouldn't rev out and was not pulling at all, the temp gauge hit 90 ish then dropped to nothing, then kept fluctuating between 60 and 90 degrees...managed to crawl over the hills down into porthmadog where I stopped the engine, turned it back on and started it and was fine after that....then it did the same on the way home when I was overtaking cars, died with no boost, turned the engine off then back on and it was ok ???? did that twice so took it easy the rest of the way
any help would be greatfull before cart it off to the garage !!!
cheers
 
Well for starters it seems your thermostat is gone. Both of my Audi's also needed new coolant temp sensors as well, and they cost next to nothing so there is no harm in changing that.

Get your car scanned for fault codes, just because nothing comes up on the dash doesn't mean there are no fault codes
 
No worries. I would put money on there being a fault code, something is putting the car into limp mode by the sound of things
 
I would check your coolant temp sensor, very common fault. If it's a black one it's the original and likely to be faulty. The new ones are green.
I would guess the car is going into limp mode due to a boost issue, more than likely over boost.
Probably find a 17965 / P1557 code set

17965/P1557/005463 - Charge Pressure Control: Positive Deviation
Possible Symptoms
  • Reduced power output
  • Limp mode
Possible Causes
  • Boost Pressure too High
  • Hoses/Pipes incorrect connected, disconnected, blocked or leaking
  • Charger Pressure Control defective
    • VNT (variable nozzle turbo): nozzles stuck
  • Solenoid Valve for Boost Pressure Control (N75) defective
Possible Solutions
  • Check Hoses/Pipes to/between Components
  • Check Solenoid Valve for Boost Pressure Control (N75)
  • Check / Clean / Replace Charge Pressure Control
    • Check / Clean mechanism for variable nozzles


Karl