Mk4 Golf TDI Turbo issue

[martin8]

Afternoon all
I've recently bought a Mk4 Golf TDI to replace my BMW as the fuel costs are getting out of hand with my daily commute to Douglas. I've repaired a stuck relay fault in the Golf's comfort module that was causing an indicator to stay on and drain the battery. Happy days.

This weekend I ran a diagnostic, cleared any faults and took it out for a short drive (long enough to get to temperature). Now I've got the following codes:

17663 - Engine Coolant Temp Sensor (G62): Open or Short to Plus - Intermittent
Should be easy enough to source and replace the temp sensor.

However, this code I'm more worried about.
17965 - Charge Pressure Control: Positive Deviation - Intermittent

There's a major lack of power after about 3500 rpm in 3rd and above, which seems to imply that it's going into limp mode and it won't got above 50-60mph. I've read that it could be that the variable vanes in the turbo are stuck open causing too much boost pressure (possibly due to the car not being used for 6 months prior to me buying it). Is there any way that I can unstick these vanes without removing the turbo from the car? Or would it be best to pay a mechanic to remove the turbo and get it cleaned / reconditioned? (I'm not confident enough at fixing things yet to have a go at the engine).

Any advise would be appreciated

Thanks

Martin

[martin8]

Hmm.. Have found this http://forums.tdiclub.com/showthread.php?t=203438, which I will give a try this evening to see if it's the actuator that's a bit stuck.. Fingers crossed.

[Taggart]

Sounds similar to mothers issue on her one a while ago, something to do with a carbon build up in the EGR (or other 3 letters, can't remember exactly)

[martin8]

Aye, could be. Plan it to remove the EGR completely and clean out the intake of all of the carbon buildup. Will probably get the turbo done at the same time. Just trying to get it working well enough for me to start using it (and to start saving up for the work that'll need doing)

[inchley313]

I'm taking a pure shot in the dark here but i seem to remember a similar fault when i worked for a vw dealership, turned out to be air mass meter!! I seem to remember that the code was different to the actual problem.

[martin8]

Cheers Ian. Will try logging the MAF tonight to see if the actual and expected values are similar.

I've been googling a fair bit and it seems like the mk4's had a fair few issues with the turbos. Luckily there is a wealth of information out there :

Boost Deviation Positive means you have a N75 that's bad/malfunctioning, actuator that's leaking, bad vacuum lines, bad boost sensor, or a sticky turbo VNT or wastegate lever. If you have a VNT turbo, it may require removal and cleaning of the vanes. See the below section for related causes. If you're getting an overboost error, it's never the MAF.

That's a fair list for me to check, although it might also rule out MAF issues. Will try N75 solenoid test (and maybe clean) tonight and test VNT actuator again (tried last night, but didn't start engine... oops).

Can anyone suggest somewhere I can get 5mm and 4mm (i think) silicon hose from? Might just replace all the hoses depending on the cost.

Thanks

Martin

[martin8]

Logged the MAF with VCDS this evening and it looks ok



Unfortunately I can't say the same for the turbo and the specified vs actual MAP



On the possible plus side, according to http://uk-mkivs.net/forums/t/353504.aspx

if the VNT rod is too short then it will effectively make the turbo far too sensitive and as soon as the ECU requests boost, before you know it you have twice the amount of boost requested as it suddenly spikes

Fingers crossed it might just be a matter of adjusting the VNT rod. It could also be the N75 solenoid sticking open as seen in the MAF image. If that's the case I should get away with cleaning it or replacing.

Now just need to figure out how to adjust the VNT rod or find someone who can

[martin8]

Mechanic mr muscled the turbo, cleaned the intake/egr and found a split vacuum hose which he's now replaced. Car is running much better but need to log it before I know for certain. Fingers crossed

[A.D.Edmundson]

Im here till sunday

Ant

[martin8]

Well, good news, turbo seems to be working properly again. Got the car back from the mechanic, was driving it to work and got limp mode. So got annoyed, turned car off and back on and floored it which seems to have unstuck the turbo

Took the car out the next day and logged it with VCDS and the actual and reported MAP values are within a percent or two and no more limp mode Time to keep the revs high to stop the turbo coking up again...