D4-D Reduced Power

[tlwatts]

Hello folks.

First post, I bought a 2002 D4-D before Christmas, it has been fantastic, but power seemed a bit (alot) peaky and lacked the expected smooth torque I'd expect in a 4wd diesel. I looked into ths and it is inherent with amm D4-Ds so I lookat at what mods might resolve this. Best I found was to chip it and the Energy-Tuning Turbotune DT module ticked all the boxes. Performance has been fantastic since! The car is now a diesel rocket!

However, on Thursday it lost power at part throttle on the motorway and ouldnt make any more power above 2k than it does below off boost. I can hear the turbo spooling at low rpm, so it seems the turbo if ok, but I have seen that the VSV valve that controlls the turbo back-pressure and therefore boost performance can stick. However symptoms also reflect the SCV valves not performing correctly, perhaps as if one valve has failed. Speed is not limited, just power, so it takes a few minuts to reach 80mph and struggles to climb hills or accelerate. No warning light has shown up though.

has anyone had experiene of these features? any ideas other than the SCV valves please? I will test the valves for electrical faults today (but I'd expect this to flag a fault and warning light on the dash, so a bit confused.

PS, even with the Turbotune disconnected the engien behaves the same way. The Turbotune alters the fuel rail pressure signal, so if it has no effect on engine performance at the moment my reasoning is that the fuel feed is not being changed per the ECU requests, and the engien is simply not making power as a result.

Someone please tell me whether I'm making sense or talking rubbish! Thanks

Tyler

[tlwatts]

Tested the SCVs for electrical fault and nothing. Didn't have time to remove them but will try do that tomorrow.

Anybody have any recommendations please?

Thanks

[yaris781]

Could possibly be an injector problem?

[anchorman]

Unfortunately you can't always tell if the SCVs are faulty by doing the electrical test. Sometimes the mechanical bits stick.

Has it stored any fault codes?

[tlwatts]

I haven't got the kit to check the codes, I bought an Ultra-Gauge but it can't find the OBD-2 protocol. Am I in error assuming the Diesel is OBD-2 compliant? If it is, does anyone know the Protocol? I can force the choice if I know what he Protocol should be.

Does anyone know how the SCV actually works? Can I remove it and apply 12V and see it moving? Any way to clean it? I expect it to look spotless since it lives in fresh clean diesel...

[Daveyonthemove]

I have seen this first hand from a tuning box, and the car was put into limp mode with 4 error codes.

I cant remember the codes, but they related to the fuel rail pressure, and once the codes were reset it was fine, however the box would put it into limp mode again, and had to be replaced.

It may be that your box is faulty, or if you adjusted it yourself, it may need tuning down a bit.

[tlwatts]

Dave, I have completely removed the tuning module (it has a bypass setting which had no change in effect) however the engine/ECU did not through up any warning light, just very reduced power! So Im a little confused.

Any info on the OBD2 situation please folks? I can check codes if I can use my Ultra-Gauge through the OBD2 port. Any suggestions/info?

[shcm]

OBD only came in for diesel for existing models, in europe, for 2004 model years. As yours is 2002, it won't talk OBD, but Toyota protocol only I'm afraid.

There's a technique for obtaining powertrain DTCs for earlier models via flash codes. I'm sure it's been posted several times on here. Search and you may find it.