Hesitant acceleration

[Aldouk]

I was hoping that someone can give me some pointers towards a fix for this problem ...
When I'm driving in traffic (stop start) if I'm slowing down to walking pace and then go to pull away gently again there's a slight hesitation between me pressing the accellerator and the power coming on. It's like as if the first 5% of the throttle doesn't work and then you get a bit of a burst when it does. It makes it difficult to drive smoothly.
I put VAGCOM on to adjust the TPS and the graph for the throttle position adjustments seem to confirm this. When I press gently on the throttle the first 10mm of travel doesn't seem to move the pointer and then it suddenly jumps (spikes)
The rest of the throttle movement appears to be smoother.
Any suggestions?

[Scotty]

The throttle is probably the worst thing about the S4. Not sure if you're new to the car and just need to get used to it or if something has changed and you have an issue. I'll guess the former.

Many years ago I was getting training around the 'ring and the trainer also tested cars and trained the test drivers. He said that my throttle control was poor and that I was coming onto it late and not always smooth. He of course assummed I was one of the many who blames the tools (and in part he was right).

He then did a couple of laps and was astounded how poor it was. He said if he was tasked with writing a report for Audi then this would have been at the top of his list.

My car was modded but I did have it unmodded, taken back to Audi, I had the latest software put on (it was fractionally better) and then remodded. It was always the down side as any movement on the throttle with a car with that amount of torque made it difficult to drive smoothly if the surface was rough or if you were being thrown around a lot.

[nihc]

Hi,

The Throttle position sensor uses a potentiometer to measure throttle position. This is basically a metal slider on a carbon resistive track. The output from it should be very smooth.

It sounds like a patch of the carbon track has worn out on yours. The first 10mm of travel would make sense as this must be where the slider spends most of it's time when you are driving, so it gets worn out.

I think you'll need a new TPS - I don't know if you can take it apart to have a look at the potentiometer's track or whether it's a sealed unit.

Hope that helps.

Regards, Chris.

[Aldouk]

It double posted for some reason

[Aldouk]

Thanks for the reply Chris.
The weird thing is that if I'm sat idling and touch the throttle it seems to respond instantly but if I'm in gear (2nd for example) with my foot off the throttle .. when I press it there's a delay of about half a second before I get any acceleration. Then it's a bit of a jolt when it does come.
The previous poster says that they can all be like it and searching on the forums seems to confirm this.
One thing I found while searching was that a remap can cure the problems as they build in some kind of adjustment for this issue.
I've just got to decide whether the problem is worth several hundred pounds worth of remap to cure it (I'm not really bothered about getting an extra 10BHP or so)

Cheers

Hi,

The Throttle position sensor uses a potentiometer to measure throttle position. This is basically a metal slider on a carbon resistive track. The output from it should be very smooth.

It sounds like a patch of the carbon track has worn out on yours. The first 10mm of travel would make sense as this must be where the slider spends most of it's time when you are driving, so it gets worn out.

I think you'll need a new TPS - I don't know if you can take it apart to have a look at the potentiometer's track or whether it's a sealed unit.

Hope that helps.

Regards, Chris.

[nihc]

Hi,

If your TPS is broken, and it sounds like it is - mine shows a smooth increase in pedal angle - then a remap isn't going to help.

I've never had any hesitancy at low speed and/or low throttle openings.

The problem does seem to point to your TPS - if it's feeding rubbish readings to the ECU, there's nothing a remap can do about it.
With a Revo remap, for example, you can adjust the throttle aggression - the ECU will ask the engine for more load at lower pedal angles. But, that would just make your condition worse.

Regards, Chris.

[Aldouk]

Well it's all sorted now
Took it down to AMD in Woking and he went through it with a fine tooth comb.
The throttle was giving 75% of power at only 30% of throttle travel. This was causing my problems combined with the large single butterfly throttle body which causes a low RPM flat spot under load.
He "moved" the throttle (as far as the ECU is concerned) so that I need to press it further to get the same power. This has totally transformed the car and I'm very pleased. The extra BHP and torque that came with the remap will come in handy too