D40 Inconsistent performance

[Jardsoooo]

Hey guys I have a Jan 2010 build ( Thai ) manual D40 4 x 2. Lots of good things about it eg 8 to 9 LP100k around town - I do drive like a grandma I admit to get that.

No power below 1500 rpm aside - ( I have come to accept that I can never pull a boat up a boat ramp etc without hurting the clutch so I avoid such situations ) - it is actually capable of pulling very strongly above the magic 1500 rpm and it can really fly in 3rd gear.

I say it is capable because its performance varies on any given day any given hour from sluggish to rockin.

Interestingly the better it goes the better the brakes grab and I can temporarily make it quicker by ( when stationary) standing on the brake pedal.

I believe the computer that runs the thing adjusts performance to suit driving conditions ? and if so this would probably explain what is going on especially as I generally have a light foot; eg at 50,000k I still have 6mm ofbrake pads left and no noticable grooving of the rotors.

My question chaps is whether there is some way to turn the bloody auto adjust thingy off permanently.

I had a chat with a tuning shop a while ago and at the time they were unable to get into the D40 computer so I'm not optimistic but hey if you can help out pls let me know.

Regards Alec

 

[Old.Tony]

I have this thought in the back of my mind that the 2010 D40s from Thailand had turbocharger actuator issues. The problems were usually a regular thumping-like sound coming from the passenger footwell area coupled with poor performance.

There may also be something not quite right with the vacuum lines - cracks in the line would prevent them from functioning normally. It might pay to take a look at those.

Also, pop the bonnet and look at your turbo from near the bonnet hinge. You should see a saucer-shaped unit on the top that has an arm extending beneath it. Have someone rev the engine up slowly from idle to 2,000rpm. At first, the movements should be erratic without pattern, but as the rpm increases, the arm should start moving more regularly, cycling at about 2 times every second with only minor variations. If it's not, either your turbo actuator isn't working properly (possibly caused by faulty vacuum lines) or your turbocharger's vanes are sticking and that might require some $ spent on it.

 

[Jardsoooo]

Yeah thanks for the reply Old.Tony. I'll have a look over the points you mention.
Nissan replaced the actuator valve at 10,000ks but the inconsistent performance has been with the ute from day one and changing the valve did'nt change it.
I would say though that overall average performance is up a long way from when it was new.
It has definately been improving from about the 10,000 k mark but it did'nt suddenly jump up with the new valve.
I've often wondered if the computer has a function to slowly increase performance as the engine beds in.
Anyway, the noise that first alerted me to the valve problem has come back in the last while so looks like another valve coming up.

 

[Jardsoooo]

And Old.Tony do you know anything about the engine performance adapting to driving conditions - perhaps it's a bit of an urban myth

 

[Jardsoooo]

Very interesting. I just had a look as you suggested Old.Tony at the actuator valve and the arm beneath. It is moving as you described but I can feel it binding. Like it needs grease and that binding is causing the sound from the passenger side which I would describe more like a seal ( animal ) barking. Perhaps they can source me a Spanish built one this time

 

[Old.Tony]

Certainly sounds like it could be another actuator. You'd think they would make the replacements work properly.

The ECU does learn driving habits. If you're generally light on the foot it won't fuel up as much as if you are a lead foot - if you are heavy on the pedal the car will generally raise the fuel rail pressure sooner. I doubt it's an overly complex algorithm, but it does remember your habits for a while. Quick "unlearning" can only be achieved by resetting the ECU.

There are two ways to reset the ECU. The first one (in the service manual) involves a number of pedal presses, switch turns and donations to Tibetan monasteries. The second one is much simpler - disconnect your battery and press the brake before reconnecting the battery.

Of course, if you DO disconnect the battery, make sure you have the radio PIN handy and if you use the trip meter value for measuring fuel economy, write down the values first.