Annoying off throttle jerk!

[eugopnosaj 0]

I have the exact same issue, playing with the damper didnt really solve it either, i have to really really ease of the throttle so gently for there not to be any jerking. I've tested the MAF and not got any issues/codes with it so i dont think its that. Will be watching this thread closely to see if you work out the problem!

[floppyman 0]

Can some one with that problem and with vag com post theyre messured values on messurement block 5 or 6 (lambda adaptations)...

[eugopnosaj 0]

Can some one with that problem and with vag com post theyre messured values on messurement block 5 or 6 (lambda adaptations)...

 

We went through this before with mine, or at least i reset my ECU because the values weren't correct, I will run it later when i get back from the gym but they were fine the last time you saw them back in November (I had the issue back then too) but perhaps they've got worse:

 

Ok, so after replacing the suspect parts creating air leaks and resetting the ECU i now have values of:

 

O2 active im getting between 0.961 and 1.016, Idle Adapted Value 0.977, Part throttle adapted value 0.922 and full throttle adapted value 1

 

Are these better or am I now running rich?

[floppyman 0]

And was the problem still there after the reset or it came after some time?

Just read that topic... It was a good find on that isv damper box.

Edited April 9, 2012 by floppyman

[Critical_Mass 10]

Forgot to add i checked the lambda adaptation and was getting the same readings as above - 0.922 - 1 depending on throttle degree.

 

I also reset the ECU and took it for a drive. Doesnt seem any better to be honest. Will get the wishbone bushes checked. One was replaced last year for the MOT. No idea the condition of the others, but (and i know you shouldnt rely on MOTs) but they cant be THAT shagged if they passed MOT. Saying that, its almost a year on 11 months actually.

 

Is there any way to check these, check for movement in the wishbone etc?

[floppyman 0]

The reading you have there is actual lambda reading.... I was looking more to the adapted values

[VWVW 1]

On flat level ground. Have you tried using your weight to press down on either side of the front wing to check suspension travel. Does the suspension bounce excessively up and down or does it settle to its original position quickly.

 

also I am sure I read you can check for engine movement with someone standing outside bonnet open with the engine running, hanbrake on, and engage first gear to get the bite and see if there is any excessive engine movement.

Edited April 9, 2012 by VWVW

[eugopnosaj 0]

And was the problem still there after the reset or it came after some time?

Just read that topic... It was a good find on that isv damper box.

 

No, still jerky, right so values:

 

ISV Adaptation: 1.078

Idle Adapted Value: 0.875

Part Throttle Adapted: 1.055

Full Throttle Adapted: 0.906

 

What does this tell you? They seem to have changed quite a bit from before, im not getting any engine fault codes either, the whole car seems to shake though and sometimes runs bad for a while till she warms up, i say bad, to the point where it has stalled once or twice, i still think i might have an ISV issue....

Edited April 9, 2012 by eugopnosaj

[floppyman 0]

Yes it does look like your isv is playing up since your part and full throttle adapted values are good... Only your idle has as a problem

[eugopnosaj 0]

So since those values (bar the Idle) are typically good it doesn't really shed any light on the jerk

[floppyman 0]

Well... Thats where it starts to get complicated..... Since your adapted values for idle.show there might be a fault some where in the isv (its to rich the mixture). That being said, when ever you let go of the trothle the isv will kick in... It doesnt matter if youre iddling or coasting.

You could plug in vcds and log the values while driving, log the isv values, current lambda values and engine speed. With those we should be able to confirm if its related.to the isv or not

[eugopnosaj 0]

Right, looks like thats where i'll start, thanks floppyman!

[RW1 0]

Some reference data:

 

[ATTACH=CONFIG]58881[/ATTACH]

[ATTACH=CONFIG]58885[/ATTACH]

 

ISV need the duty cycle %

 

TBH I think the jerk a mechanical fault with a loose engine.

 

.

[Critical_Mass 10]

Whats the adaptation exactly?

 

RW1 whats the ISV cycle %?

 

VWVW - I've not checked the suspension, but i will. Cant see it being the problem though, sure its worth checking, but id get loads of noise too surely? Ive checked the engine mount, everything was ok. Done the check as above and it seems ok.

[RW1 0]

Lambda Active has to be within limits between 0.97 - 1.03 to be working correctly for emissions.

 

Adaption, how far off ECU requested demanded signal for the air / fuel mixture with the ISV is. Typically the value is between 0.97 & 1.03 when running correctly. The nearer to 1, the better.

 

When the ISV is called upon to function, the ECU sends it a pulsed signal which rapidly opens and closes it. As you know. This is to achieve the target idle speed based on engine temperature. It is measured as a duty cycle, or percentage of time it is open. (Time On versus Time Off). 52% - 58% is typical for the VR6 when idling when in good tune.

 

Indications outside these parameter ranges point to an ISV not operating perfectly.

 

As Floppyman has written, the ECU is not happy with the ISV

 

.

[24V Renshaw 0]

Interesting thread this :)

[Critical_Mass 10]

hmmm interesting RW1, i'll have to plug VAGCOM back in now and have a gander. thanks.

[mk4craig 0]

If you've just changed your engine mount won't it just pass the problem down to your next mount? Could possibly be gearbox mount... Just a thought.

[Critical_Mass 10]

Id agree, but had my mechanic check both front and back mounts whilst i apply the clutch with the handbrake on and said it was fine, nothing wrong with front or backs.

[Kevin Bacon 5]

Did you replace the dashpot? Jerking on the over-run suggests to me a very abrupt closure of the throttle plate.

[Critical_Mass 10]

No awaiting to hear from Enthusiasticdriver i think his username is (rich) to see if he had a spare one. I now also think there's a slight jerk when applying the throttle. Im going to change the dash pot anyway as mine does look shot.

[24V Renshaw 0]

I agree with Kev as mentioned earlier, its most likely the dashpot "damper" which is not right.

 

Jay

[Critical_Mass 10]

Anyone got one? :lol:

[Kevin Bacon 5]

I think they're only £15 from the dealer mate.

[Critical_Mass 10]

ah they still available? I'd rather get a new one!!!