Strange Throttle Problem

[Plantman]

Hi,

Has anyone come accross this before or can help?

'05 TDI 140 on 144k.

I have started to notice that the throttle isn't smooth when I apply it very lightly when moving and also when lifting off. It seems to jolt or apply too much rather than a progressive amount of throttle.

It does not do this when stationary. It is very smooth and you can pick 1k, 1.2k 1.3k revs for instance.

It has been recently serviced at a dealer and they have updated the ECU to the latest version but they say they are unable to find a fault. Fuel filter changed, Air filter changed.

It is hardly noticable in 6th gear but sure is in 2nd to 5th.

A search doesn't really bring up my issue being flagged before.

Many thanks for any help.

[Labtech]

that sounds like a fault I had with a Seat Leon and it was the potentiometer on the throttle pedal - once that was changed everything was fine

[Plantman]

Cheers, true, but it works perfectly in 6th (or appears to) and is very smooth when revving stationary.....

[Plantman]

have removed the vac pipe to the EGR and stuffed it with a golf tee to see if this will help...

Does anyone know whether this will leave it open or in the closed state?

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Hmmm, initially that felt back to the way it used to be...nice and progressive....

Think the engine stopped shaking at idle too....

Got the Engine warning light on now thought and it's beginning to feeling a bit worse again.

Will leave off for another day and see if there is a pattern.

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Well some interesting results..and some not

Today was hotter so the jerky throttle was back....so disconnecting the EGR didnt seem to make it better today....perhaps not that after all...

Disconnected the anti shake valve below the EGR and that made no difference to the car...and there is no way I could live with the jolt on shut off anyway so thank gawd it's not that..

Also did a few miles while I'd disconnected the MAF.....this was interesting...made the car feel like I'd removed the turbo....no kick at all..not sure it even span up...decking the throttle just make it pick up very slowly....like the diesels from days gone by when they were dog slow...

It did feel pretty smooth though....perhaps dodgy MAF?

Got 300 mile round trip tomorrow so everything is put back on...hope the light will go off now everything is back....if not will try a 12 hour battery disconnect tomorrow evening....

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Well thankfully the ECU was intelligent enough to realise there was no fault (since i reconnected MAF and EGR) and after a few miles, a switch off and back on the engine management light went out.

So.....I'm not really any closer....bar it only happens when its warm outside and the car is hot.......Some temp sensor?

Still managed to get an indicated 54mpg on the M5 with 10x 19in Monitors, 10x keybaords, 10, mice and 25 x desk phones in the boot