80 TDi Couple of probs/questions

[pcar964]

I experience the non-responsive throttle pedal almost always in first gear when trying to pull away. Engine gives very little power and if I give it progressively more throttle, nothing happens until all of a sudden car takes off rapidly often spinning the wheels. Makes driving in slow moving traffic very difficult and almost dangerous.

As I said, happens in other gears too after coasting with clutch disengaged or lifting foot off throttle pedal to slow down.

The surge in revs is when changing gear, so foot is already off the throttle pedal, this is much more intermittent than the loss of power.

I have not experienced any connection between the surge in revs when changing gear being preceded by lack of power.

[Marc97]

I have not experienced any connection between the surge in revs when changing gear being preceded by lack of power.

Its the other way round for me and seems more related ie:
1st, surge in revs between changes
2nd, lack of power after change when releasing the clutch and getting back on the throttle.

As I said, luckily, it doesn't happen too often BUT, I can reprodude the problem on demand.

Push the throttle to the floor with 3 quick blips, revs rise to around 4000 and hold there for a couple of seconds (my foot is off the throttle at this point) then press throttle when it returns to idle. Result: no response.

[adamss24]

Its the other way round for me and seems more related ie:
1st, surge in revs between changes
2nd, lack of power after change when releasing the clutch and getting back on the throttle.

As I said, luckily, it doesn't happen too often BUT, I can reprodude the problem on demand.

Push the throttle to the floor with 3 quick blips, revs rise to around 4000 and hold there for a couple of seconds (my foot is off the throttle at this point) then press throttle when it returns to idle. Result: no response.

You, my friend, experience what its known as Turbo Lag and in your case could be accentuated by a sticky/slow raecting/sooted-up VNT mechanism, that is common with high milleage cars driven in heavy traffic or in coffin-dodger style...!

[Marc97]

Thick mode again. Whats a VNT?

Thanks for the reply, I'll try and clean out the 'VNT' asap and report back.

PS, I have owned TD cars for quite a few years now and I am used to plenty of lag at low revs although this is my first TDi and my first electronic throttle car. The feel of the throttle is eerie in comparison to my other cars.

[adamss24]

Thats is the variable vane mechanism (the moving fins inside a Garrett turbocharger) and with carbon build up it jams and may set a code in the memory. If your turbocharger is wastegated(KKK) then you may disregard this thread as its operates differently and if faulty you should check for a stuck open/close wastegate that will trigger a overboost/no boost code and one should check the vacuum hoses for splits and cracks leading to similar symptoms. Generally KKK turbochargers are a bit more reliable but the Garret ones are more common and easyer to tune and much cheaper...!

[Marc97]

Cheers, my car has an actuator on the turbo so I guess that means its a KKK?
I have checked all vaccum pipes but they are all fine, I'll have a play with the actuator/wastegate and clean the wastegate hinge tommorow.
Will the overboost code remain on the ecu and stay as a fault?
Will it affect the car until it gets cleared?
Can I clear it by disconnecting the battery lol??? (well it is an old car, it might not have the same memory capacity as all the spritely younger cars )

Cheers Adam,

Marc.

[adamss24]

Cheers, my car has an actuator on the turbo so I guess that means its a KKK?
I have checked all vaccum pipes but they are all fine, I'll have a play with the actuator/wastegate and clean the wastegate hinge tommorow.
Will the overboost code remain on the ecu and stay as a fault?
Will it affect the car until it gets cleared?
Can I clear it by disconnecting the battery lol??? (well it is an old car, it might not have the same memory capacity as all the spritely younger cars )

Cheers Adam,

Marc.

They will stay logged in the memory until you disconect the memory. Newers models logs them onto a non volatile memory that will hold for a while(dont know how long). Turbo related faults will/may trigger Limp Mode and will clear as soon as you stop/start the engine again until the condition that make it reocurs.

[HF1600ie]

I dont believe the 1Z engine of the Audi 80 has a VNT type of turbine, which means "variable nozzle turbine". The Geometry of the turbo does not vary (it does in the AFN engine of the 1996-99 110bhp Audi A4, for example).
So, the vanes of the turbine only get damaged with carbon deposits due to low traffic and slow driving in other TDi (recent) engines.

However, i do experience an excessive "Decreasing load" when shifting gear, feeling that the ECU injects extra-fuel to sweeten the gear changed. I have to lift the right foot a bit before the clutch, otherwise i will experience an increase in revs while shifting gear.
My Seat Ibiza with AFN engine 110bhp, doesnt have this , and honestly goes sweeter. Something in bettween could be more useful. Thinking of an ECU remap to fix this and and a bit of extra power.

Cheers

Henrique

Portugal

Thick mode again. Whats a VNT?

Thanks for the reply, I'll try and clean out the 'VNT' asap and report back.

PS, I have owned TD cars for quite a few years now and I am used to plenty of lag at low revs although this is my first TDi and my first electronic throttle car. The feel of the throttle is eerie in comparison to my other cars.

[adamss24]

I experience the non-responsive throttle pedal almost always in first gear when trying to pull away. Engine gives very little power and if I give it progressively more throttle, nothing happens until all of a sudden car takes off rapidly often spinning the wheels. Makes driving in slow moving traffic very difficult and almost dangerous.

As I said, happens in other gears too after coasting with clutch disengaged or lifting foot off throttle pedal to slow down.

The surge in revs is when changing gear, so foot is already off the throttle pedal, this is much more intermittent than the loss of power.

I have not experienced any connection between the surge in revs when changing gear being preceded by lack of power.

I take it you never drove a diesel prior to this car, innit ? Thats common with TDI due to their relative high torque compared with a similar petrol engine. You will soon adjust your driving style as when releasing the clutch it needs a light blip and you are away, no need to accelerate and then quickly accelerating trough gears. Because of the torque, you will find its not necessary to downshift so often as with a petrol car ! Also you will see that its easyer to drive a manual diesel in slow moving traffic as the engine will pull in second or third at tick-over and returning better Mpg. I have trouble adjusting my driving style when i drive missus polo 1.4, i mean its either underreved or overreved and it takes about 5 min to adjust my usual heavy foot to the light featherweight acceleration of the polo. I often stall the polo when i drive off from a stand still but i never stall my diesel. When i need it to go slow- i use i light foot and when i wanna go fast i just boot- it.