Something funny going on?

[jonesfam]

2004 D2a TD5.
She has been running really well unless I accelerate hard?
So basically cruise on up to 110kph or about 2600rpm & all good, try to accelerate above 3000rpm & the car reves, drops reves reves, drops reves.
Try to build up speed quickly & the same thing. Also does it on hills, not that we have many.
Seems to rev to 3200 or so then drops back under 3000rpm.
It's like it's surging, revs up & down very quickly.
Not fun when overtaking!
What should I be looking at? I am thinking it's either a fuel or air problem?
Any help would be great.
Jonesfam

[Tombie]

Check waste gate and actuator.

[Tins]

Check waste gate and actuator.

X2

[jonesfam]

Check waste gate and actuator.

How?

[maxperformance]

I had both of the Auto Td5 and Manual Td5 with this exact same problem.

My very first Auto Td5 was actually the problem of waste gate actuator at a wrong setting. You should trying to adjust it SEVERAL TIMES (in my case it took me about 50 times, and each time included a hill drive test) to get its right spot.

In my D2a Td5 Manual, the issue came from a bad MAF sensor. A replacement of VDO MAF sensor solved the issue (and I should mention that a cheap Chinese one from eBay wasted me $39 after just a day of use).

[Markf]

It'll very likely be one of the waste gate solenoid hoses either split or cracked. Cheap and easy to replace all three of them.

[sierrafery]

Or it can be the solenoid dead as well www.discovery2.co.uk / Waste Gate Modulator - Over boosting (http://www.discovery2.co.uk/wastegate.html) in many cases if the problem goes away with fuse F2(engine bay) removed you need new solenoid but on facelift that symptom can be caused by bad MAF as well so try with it unplugged first cos removing F2 will disable the MAF too

[scarry]

Faulty MAF was the issue on my D2a,the symptoms were similar to the OP's.

[Graeme]

A failed wastegate modulator on my MY99 caused the same problem - failed on the unlimited position so the ecm would cut fuel due to excessive boost pressure.

[Tombie]

Easiest way to test that is bypass the modulator unit, run the hose from the turbo outlet pipe (small hose coming up from the side) directly to the turbo waste gate actuator and go for a drive.

[AK83]

Easiest way to test that is bypass the modulator unit, run the hose from the turbo outlet pipe (small hose coming up from the side) directly to the turbo waste gate actuator and go for a drive.

This.

And I've read and experienced what will more than likely happen, is it will then go with too much boost, and cause a fault(or go into limp mode). Turn off car it resets if it goes into limp mode.

Very easy to do, maybe have some needlenose pliers to undo the clips on the hoses. Don't worry about any flopping about hoses for a bit, just a test drive to confirm WGM is at fault.
If it is, easy to change yourself too.

[pjh4159]

2004 D2a TD5.
She has been running really well unless I accelerate hard?
So basically cruise on up to 110kph or about 2600rpm & all good, try to accelerate above 3000rpm & the car reves, drops reves reves, drops reves.
Try to build up speed quickly & the same thing. Also does it on hills, not that we have many.
Seems to rev to 3200 or so then drops back under 3000rpm.
It's like it's surging, revs up & down very quickly.
Not fun when overtaking!
What should I be looking at? I am thinking it's either a fuel or air problem?
Any help would be great.
Jonesfam
It sounds like the copper sealing washers under the injectors are failing and need replacing, I had very similar issues when the engine was under load up hills or accelorating. After replacing these washers and O rings under the injectors the fault disappeared.

[vbrab]

It sounds like the copper sealing washers under the injectors are failing and need replacing, I had very similar issues when the engine was under load up hills or accelorating. After replacing these washers and O rings under the injectors the fault disappeared.

Had something similar on a TDi300 where it would run and pull quite well until I wanted it to go a bit fatser or it had to work a bit harder, then it would just lose power.
In that instance I found that although I had been chnaging all fuel filters regularly, there had been a bit of deritis caught on the small elbow on the inward fuel line to the rear filter, and when I needed increased fuel flow I wasn't getting it.
Undid the line end into the filter and cleaned it out with a thin piece of plastic (zip tie), cleared out some bits of rubbish that somehow had caught up on the elbow leading into the filter and the problem stopped.

[jonesfam]

Today I have time to look at my turbo waste gate.
I have lubricated & moved the little lever 1000 times.
1. The lever does not feel like it's connected to anything, should it?
2. When I let the little lever go it flops to the a middle down position, I thought it was supposed to spring to the cabin side, wrong or correct?
Jonesfam

[PhilipA]

If you are talking about the wastegate lever itself IE the tiny 13MM long shaft that goes into the exhaust side of the turbo, then it should not feel resistant, as that is the role of the wastegate actuator .

It is just connected to a flap inside which is opened and closed by the shaft from the pressure diaphragm in the actuator.

If you are talking the actuator, you need a new one.
Regards PhilipA

[jonesfam]

Thanks Philip,
Yes it's the lever on the turbo.
I can't budge the actuator shaft.
The lever did not feel really very stuck when I first touched it, it was not loose but not real difficult to get moving, just a bit of a wiggle & moved.
Since lubing it it is now really fee.
Jonesfam

[jonesfam]

Well, it ain't the Waste Gate, unless it's the actuator?
Just went for a spin & wont go over 2500 - 2600 RMP.
I have now pulled the MAF thing out & hit it with a dose of cleaner.
Once that dries I will re-install & try again.
If that doesn't change thing I will try with the MAF unplugged.
There is a thin film of oil or similar on the air inlet pipe.
Jonesfam

[trout1105]

The old girl is simply chucking a wobbly because she knows that you are going to sell her [bigwhistle]

[jonesfam]

I don't think it's the MAF, no change after clean & no change with it disconnected.
So I'm thinking maybe the waste gate activator thing.
I will look about for a new one.
Jonesfam

[Markf]

I may be thick and I missed it but have you checked the three small diameter tubes connected to the waste gate solenoid for cracks and / or splits?

[Graeme]

The wastegate chamber can be tested with some compressed air directly into the chamber's inlet port. The wastegate should be fully open without any pressure and fully closed with about 1 bar of pressure. If the chamber is working OK then the modulator can be bypassed using a length of hose directly between the port on the turbo outlet tube and the chamber. This will limit boost to about 1 bar so performance will be down a little compared with a working modulator.