I have an X plate 1.8T Octy, which has been suffering an intermittant problem over the last couple of months.

If I drop down to 3rd gear to overtake a tractor, the car pulls away fine with the revs increasing quickly and I can hear the turbo whistling. Once the revs get beyond 3500-4000 rpm, the whistling stops as if the turbo has run out of range, the car then starts to get a bit jumpy, and for the rest of the journey pressing the throttle doesn't make the car accelerate as well as before, no matter which gear I'm in - there's either no power at all, or there's a delay before the turbo kicks in and the car lunges forward. Stopping, switching off and restarting used to solve the problem, but more often than not it doesnt anymore. Is it a problem with the turbo, plugs, HT leads??

If anyone has any suggestions, they'd be gratefully received!!!

Boost leak? Check all of the boost hoses for splits.

Edit: If you can get someone to scan it with VAGCOM it would help a lot

Edited 17 July, 200916 yr by RobClubley

Couple of things id try as it sounds similar to what my car did intermitently (1.8T too, non VRs) the ignition ignitor on the airfilter box, unplug both plugs and put some electrical grease or vaseline on the contacts and pop them back on as this can cause missfires, and do you get a ticking type noise aswell?? as i found the 3 bolts holding the turbo to the manifold had come loose, tightened them and problem gone, was very strange that the loose bolts created an intermitent fault!

Couple of things id try as it sounds similar to what my car did intermitently (1.8T too, non VRs) the ignition ignitor on the airfilter box, unplug both plugs and put some electrical grease or vaseline on the contacts and pop them back on as this can cause missfires, and do you get a ticking type noise aswell?? as i found the 3 bolts holding the turbo to the manifold had come loose, tightened them and problem gone, was very strange that the loose bolts created an intermitent fault!

I have the exact symptoms on my vRS, however i've also got problems with my temp guage. Already changed the temp sensor, thinking it may be thermostat??? I've got the ticking noise, with intermittent boost, sometimes nothing and other times lunging. As Jimbob said, if i stop, turn the engine off and back on again, it's almost as if someones just flicked a switch and all of a sudden the turbo is working again. Very strange. :confused: Turbo120Fabian dyou have any pics of what you thought would be a good solution?? greasing the ignition contacts??

With a description like this, it sounds like an over-boost problem. Have you had the fault codes checked?

Once the revs get beyond 3500-4000 rpm, the whistling stops as if the turbo has run out of range

The whistling should die down about then anyway on a standard (non-mapped) car as the boost peaks at 3000rpm and that's when the wastegate opens.

Still doesn't explain why it's juddery at those higher rpms though :confused:

New N75 valve

New N75 valve

Easy enough job to replace? Do i need VAG COM to reset?

easy job, replaced mine a while back, 3 pipes (the pipe clamps can be quite tricky to release iirc) and one electrical plug. no need for vag.com to reset. cured my on/off, on/off boost problem. think they're around £40 from the stealers. if i can find the old one i'll furnish you with a part number

Many thanks for all the replies - plenty of things to try out during this week! My brother (who's a tractor mechanic!) came over yesterday and gave the throttle body a good clean for me as i'm hopeless with cars....it was pretty grubby and the flap wasn't working properly. Have given it a good drive today with no problems, but will give it a few days and see if it's solved. If it comes back, I'll give some of the other suggestions a go. Once again, thanks for your replies!