Thread: D2a TD5 loses power at WOT on hills

I found this thread which is of interest - http://www.aulro.com/afvb/technical-...ml#post1450413

I think you are on the right track. Your problem does seem to be boost or fuel related. You could by pass the modulator with a piece of vacuum hose to exclude this as the fault.

If it isnt the modulator and it isnt hoses delaminating, you only have 2 other options. One is the throttle position switch.
You can attempt to replicate the fault using cruise control, if no fault with the cruise engaged it will be this switch.
If not any of these then it may be fuel pump. Check out the good oil on fuel pumps, turbo and hoses.

Another thought which comes to mind since yours is a 2a.
Is the Cat still fitted after the turbo pipe or has it been removed?
D2a owners have experienced the Cat collapsing and restricting the flow. Some at high revs others at all revs.
Your symptoms seem too rapid in onset for this to be the problem, but worth keeping in the background till sorted.
The Cat is not a legal requirement on this vehicle so can be removed.

Cheers

Originally Posted by strangy

I think you are on the right track. Your problem does seem to be boost or fuel related. You could by pass the modulator with a piece of vacuum hose to exclude this as the fault

What is the purpose of the modulator if it can just be by passed? What will happen if it is bypassed, does that mean it should drive up the hills fine indicating that the modulator is the issue?

Originally Posted by strangy

If it isnt the modulator and it isnt hoses delaminating, you only have 2 other options. One is the throttle position switch.
You can attempt to replicate the fault using cruise control, if no fault with the cruise engaged it will be this switch.

The issue also occurs with cruise control on. The first few times it ever happened was when traveling down the Hume Highway between Canberra and Melbourne on cruise control. So I assume that means that the throttle position switch is not likely to be the issue then.

Originally Posted by strangy

Another thought which comes to mind since yours is a 2a.
Is the Cat still fitted after the turbo pipe or has it been removed?
D2a owners have experienced the Cat collapsing and restricting the flow. Some at high revs others at all revs.
Your symptoms seem too rapid in onset for this to be the problem, but worth keeping in the background till sorted.
The Cat is not a legal requirement on this vehicle so can be removed.

The cat is no longer there, so that cant be the cause.

twr7cx;1450474]What is the purpose of the modulator if it can just be by passed? What will happen if it is bypassed, does that mean it should drive up the hills fine indicating that the modulator is the issue?

The modulator is essentially an ECU activated by pass valve. It will operate to open your turbo wastegate actuator, reducing boost to ensure max boost parameters are not exceeded. If you by pass the modulator you can exceed boost parameters and put the ECU into limp mode. A restart will reinstate normal opeartion. With gentle throttle use, up to full, you will prove the modulator working or not and the worst you will do (for a once off short term test) is put it into limp mode. If you find it is the modulator dont run it hard in the bypassed state until you replace the modulator.

The issue also occurs with cruise control on. The first few times it ever happened was when traveling down the Hume Highway between Canberra and Melbourne on cruise control. So I assume that means that the throttle position switch is not likely to be the issue then.

Yes, This is good news as you now have ruled out the TPS

Is there any smoke when this happens?



Cheers

Originally Posted by strangy

The modulator is essentially an ECU activated by pass valve. It will operate to open your turbo wastegate actuator, reducing boost to ensure max boost parameters are not exceeded.

If you by pass the modulator you can exceed boost parameters and put the ECU into limp mode.

Tombie> If you bypass the modulator you actually reduce boost by forcing the wastegate actuator to cut in earlier.

Tombie> The Modulator is a bypass, that bleeds boost away from the wastegate allowing the boost to spool up quicker from launch before cutting over and actuating the wastegate.

A restart will reinstate normal opeartion. With gentle throttle use, up to full, you will prove the modulator working or not and the worst you will do (for a once off short term test) is put it into limp mode. If you find it is the modulator dont run it hard in the bypassed state until you replace the modulator.

Tombie> Running it hard will result in the symptoms described by the OP on hills. The boost is falling away reducing power under load.

Yes, This is good news as you now have ruled out the TPS

Is there any smoke when this happens?

Cheers

To check the modulator, take it off and blow through it....
The port going to the turbo wastegate will be bleeding boost if jammed shut. If jammed open the vehicle will overboost and will be noticed by the 'jerkiness' of overboost fuel cut-out.

Thanks Tombie refreshed the memory there....apologies twr7cx for misleading info.

Originally Posted by Tombie

To check the modulator, take it off and blow through it....
The port going to the turbo wastegate will be bleeding boost if jammed shut. If jammed open the vehicle will overboost and will be noticed by the 'jerkiness' of overboost fuel cut-out.

So ideally when removed when I blow through it it should be closed, this would mean that it is fine. If it is open it means that it's buggered.

Originally Posted by twr7cx

So ideally when removed when I blow through it it should be closed, this would mean that it is fine. If it is open it means that it's buggered.

It has 1 inlet at bottom
1 outlet top. 1 outlet to the side.

Following the hoses will tell you which is bypass and which is wastegate.

I can't recall right now which is which.

When in non actuated mode air should flow through the bypass port.