QD32 Power Surging Issue Help needed

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goldpoacher

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I have a 1998 Navara DX22 with QD32 which is revving between 1800 - 3000rpm why idle or under load.
The Injector pump and injectors reconditioned two months ago, I have checked rail fuel return line for blockage, changed oil and filter, removed air inlet manifold and engine still surging with manifold off.
It is a simple diesel setup that has me stumped, any help or ideas appreciate
 

doug696

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hey mate, my first thought was the banjo filter on the inlet to the injector pump but i'm not sure that surging is 1 of the symptoms, the only other thing that i would check for is air in the fuel line, i'm not sure mate just spitballing, i think i would take back to who ever did the pump and injectors just to make sure
cheers doug
 

goldpoacher

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Contacted Diesel Centre and they are stumped as well as I sent them a video, problem being 600km from repair centre.

If it was Fuel Stavation it be easy to work out, but this is opposite as it will rev between 1800-2800 rpm continually at idle or load, but will fluctuation a lot less if throttle maintained at approx 2000 rpm
 

Old.Tony

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Just an idea. May not work, but it's free and if it's right, could save you an engine.

Disconnect the hose that runs from the top of the camshaft housing to the air intake (PCV)) at the point where it joins to the air intake. Aim the hose toward the road. Block the pipe that you disconnected the hose from so that unfiltered air can't be sucked into the intake.

With that hose no longer feeding blow-by into the intake, start the car. You want to look for two things: first, how's the idle - and second, if you hold a clean piece of paper and aim that hose at the paper, do you get much oily residue appearing on the paper?
 

Mikevp44

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It's possible you might have a failing tps (throttle position sensor) sending a false voltage reading to the ecu and then to the electronic control module on the pump.

Cheers
 

doug696

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hey mike, there is no tps or ecu everything is mechanical on these beasts [qd32]
cheers doug
 

Boriskov

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Check the fast-idle cable. If it's stuck, it'll cause this.

Check visually by seeing if the throttle cam is hitting the stop when closed.. If its not this, try adjusting the idle. (Looking from the drivers side, its the top adjustment).

Also, just because injectors are reconditioned, doesn't mean it's not the problem. Leaking tips an cause fast idle and smoke. How are the EGT's?
 

Peter d40

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I have a 1998 Navara DX22 with QD32 which is revving between 1800 - 3000rpm why idle or under load.
The Injector pump and injectors reconditioned two months ago, I have checked rail fuel return line for blockage, changed oil and filter, removed air inlet manifold and engine still surging with manifold off.
It is a simple diesel setup that has me stumped, any help or ideas appreciate
hi i have a very similar problem with a D40 4.0 petrol did you find the problem?
 

Peter d40

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Hi Peter,

This might be a timing/advance issue in the petrol engine, they have quite different quirks to the diesels.

What year is yours?
Hi Tony, thanks for your reply, it’s a 2008 4.0 V6, manual. I have been away so haven’t had a chance to do any more with it as yet. But keen to sort it out
 

Old.Tony

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Looking at the wiring diagrams for the VQ40 engine, each coil is triggered directly by the ECU, so timing will be taken off the crankshaft position sensor (located on the oil pan).

This can be interferred with by debris in the teeth - that's happened before, usually a sign of something else going wrong. Inspection of this is needed (one bolt, one electrical connection).
 

Peter d40

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Looking at the wiring diagrams for the VQ40 engine, each coil is triggered directly by the ECU, so timing will be taken off the crankshaft position sensor (located on the oil pan).

This can be interferred with by debris in the teeth - that's happened before, usually a sign of something else going wrong. Inspection of this is needed (one bolt, one electrical connection).
Thanks Tony. I will take a look at this
 

Louis

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Hi guys. Check if your acceleration pedal is electronic. If so unplug it, and see what the rpm does when idling.
 

Louis

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Mine seems to be faulty. After unplugging. Rpm back to normal
16621858562714254759859263960006.jpg
 

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