Jerk when power comes off

[robinm]

Hi

I mentioned this once before.
When I take my foot quickly off the throttle quickly the power doesn't come off smoothly and there is a bit of a jerk. It's not a huge effect, but doesn't feel that great.

Someone suggested the Lambda probe, so I checked the blink codes and nothing. Will a bad Lambda probe always give a blink code fault?

Another thought I had was the throttle damper. Maybe mine is not damping enough? How long should it take to extend/retract? Are there any other tests. It seems like a pretty simple bit of kit.

The car is a 93 S2 aby.

Thanks for your help yet again.

Loving the car, just need a new PAS pump at some point and to sort out this jert thing, and it'll be perfect.

Cheers

[dan_b]

It could also be your gearbox/ rear diff bushes are worn and are not absorbing the shunt from the drop in power as smoothly as they used to?

[martinjs]

Hi, are you using an aftermarket dump valve? could be throttle position sensor maybe. I have a similar problem.

[robinm]

It doesn't feel like a transmission clunk. There is no noise. I'll try and give the system a good shake next time iit's on ramps.

Dump valve and throttle position sensor - not sure, are there checks/fault codes for these?

[GandalfS6]

Does it happen when you are on boost and off boost? If it only happens if you were on boost it is most likely the Throttle Bypass Valve (aka Diverter Valve or dump valve - technically a dump valve is not the same as a diverter valve but they perform the same basic function in different ways) that is faulty. The TBV releases boost when you get off the throttle so it is probably sticking.

It is not expensive to replace (GBP15 from Vagparts for the S3 TBV IIRC).

[Rusty]

Mine gives a jolt when you let off at full boost but then I haven't got a throttle damper on it cos it broke off. Adjust the damper correctly and if it still does the same thing you know it's not due to the damper. Best to eliminate the simple things first. I'm sure there's a thread somewhere about it.

[quattronutter]

i had similar problem,throttle cable was slightly too tight,grease all the moving parts on the throttle body too,you will feel the difference after...

[robinm]

Thanks for the help.
I'll make sure the damper is set correctly with 5.5mm bit. The adjusting nut still has yellow paint on it to mark it's position, so has not been fiddled with.
Then I'll try the TBV seeing as it's cheap.
Where is the throttle position sensor?
cheers
robin