Thread: D4 Performance Restricted

There is a procedure for testing it that involves disconnecting the valve'e vacuum line at the top front of the engine. However the access panel behind the front right wheel is quite easily removed which then allows you to use your hand to operate the valve's lever which is on the engine side of the valve. If the lever's movement is being restricted by grit then you will feel the stickiness of movement, which will be freed with a few movements of the lever and perhaps a squirt with a liquid (water?) to wash away the dirt.

Edit: Blipping the throttle or high engine revs without a load wont cause the valve to operate.

Thanks for your reply. How hard should it be to move the valve, like it moves smoothly but it's very hard. As a further development, I got an engine management light tonight at the same time as the restricted performance warning, first time that's happened, does that give any further clue to what it might be?

Perhaps coincidental but my D4 started with just the message occasionally then progressed to more frequently then the warning light as well over several days.

The valve isn't difficult to remove, held on by 3 bolts (IIRC) and 3 hose clamps to undo. Mine hasn't re-occurred since being cleaned but I expect it will when enough dirt accumulates.

I targeted this valve because mine's several fault codes all related to inlet air pressure discrepancies and there were reports of this valve being a regular culprit.

So I took it off and gave it a good clean today, mechanism was working nice and smoothly so I had my fingers crossed. Low and behold restricted performance has shown again. I've noticed that usually it is occurring after slowing from a run above 70kph with the RPM always below 2000. With no knowledge of how the vacuum system in this vehicle operates I'm wondering if it could be something to do with that and it operating the actuator. I say this because I've also noticed recently, sometimes around when it happens, the brake pedal loses its feel, to the point where pedal travel can almost be to the floor before they bite, if I pump it slightly a couple times though it returns to normal? Could this be related?

Cheers

Your brake pedal behaviour is far from normal.

There are lots of causes of restricted performance so fault codes need to be read. I had one recently that emanated from the gearbox ecu (TCM) triggered by a gearbox malfunction. Your's may be due to a disconnected vacuum hose somewhere or perhaps the primary turbo's actuator rod joint being sticky.

Is the primary actuator rod the one on the pax side of the engine right next to the battery compartment, black plastic rod?

How much should it be to get codes read, LR here in Perth wanted to charge $170 for it! Seems a bit much just to plug the thing into a computer.

Is it possible these issues are related? The brake pedal thing isn't all the time, in stop start traffic it's not there because you're constantly on and off the brakes, but after a run up the freeway braking on the offramp will be where it's worst, then "Performance Restricted" often follows.

Thanks

The primary turbo is on the passenger side and the rod is at least visible under the mudguard over the top rear of the wheel but may also be visible from above. I don't recall its colour but I was able to get to mine to check that its joints were free to move.

The 2 faults may well be connected but I would be pursuing the brake pedal misbehaviour which may lead to uncovering a disconnected vacuum hose somewhere.

You would do well to purchase a code reader tool specifically for the Disco because some problems are easily solved once the codes are known. You can also get remote advice from knowledgeable people on possible causes if the codes are known. Some tools only read and clear codes whilst others allow some settings to be changed. Depending on what you see yourself doing, spend less or more but only do it once.

Originally Posted by ZKEHY

Is the primary actuator rod the one on the pax side of the engine right next to the battery compartment, black plastic rod?

How much should it be to get codes read, LR here in Perth wanted to charge $170 for it! Seems a bit much just to plug the thing into a computer.

Is it possible these issues are related? The brake pedal thing isn't all the time, in stop start traffic it's not there because you're constantly on and off the brakes, but after a run up the freeway braking on the offramp will be where it's worst, then "Performance Restricted" often follows.

Thanks

I can read the codes for you - we charge $30. PM or email me.

Cheers,

Gordon