Newbie with Limp mode problem on Bora TDI PD

[nksparky]

Hi guys....

I'm hoping that someone may add to the knowledge that I've already gained from the many existing threads about turbo loss and limp mode (it's made me realise how little I know about this sort of thing).

I have a Bora 115 TDI PD which has been "Revo'd" to 150bhp. A year ago I had the common problem in that under heaviesh load at speed, the turbo stops and limp mode starts. The problem is now back.

I have the Revo switch which allows me to go back to stock 115bhp but the problem still occurs under the same conditions. Are there any conclusions that I can draw from this ?

I plan on following the tips gained from the forum - checking hoses, N75, cleaning intake and EGR but is there anything else that is simple to check (I've already unplugged the MAF and it's worse) ? Also, if the problem is a build up of soot in the intake or in the turbo, will fuel/engine diesel treatment addatives help or even engine flush just before an oil change ?

I plan on getting VAG COM but it's out of stock for 2 weeks at Ross-tech so I don't yet know the error codes and I'm not keen on main dealer...

Any help is much appreciated...

[Rustynuts]

Check the VNT mechanism on the turbo. This is a vaccuum controlled (by the N75) actuator which makes the turbo develop more boost. If it's sticking then the boost doesn't match with what the ECU is asking for and limp mode results.

This is a picture of what it does.

The actuator arm is fixed to the turbo housing and you may need to get under the car to see it. There should be 3/4 - 1 inch movement when boost is called for. See if it'll move by hand (Engine turned off for this!).If not, a squirt of wd40 and a pair of pliers to move it should get it going. It gets all carboned up inside and restricts the movement.

[nksparky]

Cheers Rustynuts. That's one more on the list to check and do this weekend....fingers crossed.