Erratic boost

[Thomas]

Hi guys, something not quite right with the car. Octavia 1.8T, when driving I feel as if the power just suddenley disapears. The boost usually holds at 12 but now it goes to 14 then 8 then 14 then 8 and so on. It feels like some thing gets stuck and this seems to sap the power, then it sometimes frees up and the power comes straight back. Also I can usually drive at 30mph in 5 gear but now it judders when I do so. Any help will be welcome. Thanks.

[cheezemonkhai]

NOt sure but the obvious thing to check are the hoses.

[Manguish]

Is it remapped with a boost controller?

[Thomas]

Yes it is remapped, no boost controller. Drove it this morning and it was fine, but problem arrose again this afternoon.

[texasjohn]

Do you have the stock Bosch diverter valve fitted?

They have been known to fail on chipped cars, the plastic can't stand up to the increased forces.

This of course has NOTHING to do with the fact that I have a Forge-type metal diverter valve for sale in the 'for sale' section!!!

[Thomas]

No, when I bought the car it was cracked so had another one fitted, not sure what one, but it is just plastic. If leaking boost is the problem would this also account for it being juddery at low speed?

[Manguish]

Hmm.. Mine had the same problem, turned out it was a faulty boost controller. Basically a variable resistor. Replaced it and all was well.

[texasjohn]

No, when I bought the car it was cracked so had another one fitted, not sure what one, but it is just plastic. If leaking boost is the problem would this also account for it being juddery at low speed?

To be quite honest, I am not sure!

I think that when the DV breaks/cracks, the car has trouble holding boost at the same level (i.e. needle on boost gauge 'wobbles' at WOT)

[Thomas]

Hmm.. Mine had the same problem, turned out it was a faulty boost controller. Basically a variable resistor. Replaced it and all was well.

Really, could be whats wrong with mine. No error codes thought, how could I check the boost controller?

[Manguish]

I thought you said you didn't have one?

A small k no b you can twist to turn the boost up/down.

If you do find one, simply unplug it and the stuttering will go away if it's faulty. Mine was going open circuit.

[Thomas]

I thought you said you didn't have one?

A small k no b you can twist to turn the boost up/down.

If you do find one' date=' simply unplug it and the stuttering will go away if it's faulty. Mine was going open circuit.[/quote']

No I don't, I thought you were refering to some kind of inbuilt, oem boost controller that may have had a faulty resistor.