D40 YD25 Engine surging

[MoFo]

I have a 2006 D40 YD25 Navara STX. 210,000 kms. The following has been replaced or cleaned; Suction Control Valve (SVC), Vacuum Turbo Boost Control (TBC), Fuel Pressure Relief Valve (FPR), Cleaned Mass Air Pressure (MAP), Replaced Fuel Filter, Replaced Air Cleaner Element, Replacement of all vacuum hose tubing. Resetting of ECU. Cleaned Diesel Particulate Filter (DPF) 40,000kms ago, ~ Still surging under load. What have I missed?

 

[Old.Tony]

Have a look at the air path between the turbocharger and the inlet manifold. Any black oily emissions along that path could be a sign of a boost leak. Follow the hose forward from the turbo to the intercooler, check both sides of the intercooler, then the large hose from the intercooler up to the inlet manifold.

Otherwise, you might have an EGR valve fault, the easiest way to determine this in a car of that vintage is to just block the EGR right next to the valve by cutting a 1mm thick piece of stainless steel and shaping it the same as the gasket but excluding the large central hole. I may or may not have done this myself (no confessions here!).

 

[MoFo]

Hi Old.Toni, yes I blocked of the EGR valve and loved the subsequent increase in responsiveness. Now I've now reverted back to a plate with a 10mm hole drilled through the centre. Lossed a heap of grunt and responsiveness, however I need to make sure that this is not the cause of the problem. I don't think this the cause. I'm now thinking the DPF is the problem. It was removed and cleaned 40,000km's ago, then reassembled back into the exhaust system. Is there a kit you can apply at home to the DPG to clean it? Any thought's?

 

[Old.Tony]

The DPF shouldn't cause surging. It's in the exhaust past the heavy restriction of the turbocharger's turbine housing, past the dump pipe's elbow (another restrictor to gas flow) and past the catalytic converter. It's the last thing I'd suspect to be responsible for surging. A fault in the DPF internal sensors or in the pressure sensor (up on the inner left hand guard near the ABS unit) should result in the DPF light and some excess smoke, but not surging as the smoke is caused by post-combustion injection (injecting in the exhaust stroke while the exhaust valve is open) - the cylinder isn't producing power at this point in the cycle.

A 10mm hole under pressure will still allow a fair amount of gas through and if the EGR valve is sticking/responding slowly/faulty it's possible that it's causing the surging. A 2006 model YD25 won't have a flow sensor in the EGR valve anyway, so blocking it completely won't produce any errors.

 

[ericcs]

interesting, the 06 series1 with the low mount turbo, shouldn't have a dpf at all, only a cat. and a dpf was only in auto's from 07(series2), manual's didn't have them.

 

[MoFo]

Hi ericcs. Thx for your response and also Old.Tony's as well. Very much appreciated. This is a Automatic Transmission model. Built October 2006 in Spain. It definitely has a DPF as I saw the orange light come on, took it to the DPF specialists and they cleaned the unit out, charging me accordingly ~ appox. $700.00, about 40.000kms ago. I'll never forget it mate. If it's not the DPF like Old.Tony suggests, then maybe it is the EGR valve. After bolting in blanking plates with and without holes in them for 000's of kilometers , they have made Zero difference to the surging. How do I check if this valve is operating correctly without purchasing a new one?
P.S. All the piping after the turbo is 100% sealed. No leaks at all.

 

[Old.Tony]

If you've put in a full blanking plate and it still surges don't worry about the EGR valve, it will have no effect at all.

The next thing to check is the slippage of the auto transmission fluid drive. These can and do wear, particularly the clutch that locks the torque converter above 70km/h. There will not be any codes present for this either, but a mechanic workshop scan tool plugged in to the OBD port can read the slippage and determine if the TC is faulty.

 

[MoFo]

Thanks Old.Tony. That is exactly what I will do next. I have a auto trans guy picked out. This is my first forum and I thank everyone for there help so far. I'll report back after they checkout the auto trans.

 

[MoFo]

Hi Old.Tony, As promised, I'm writing back to you not only to finalize the thread as promised, but also in the hope it may save someone somewhere the expensive guessing game I have just been through. After 4 weeks at the local Nissan dealer here in Brisbane, the fault was finally discovered. The turbocharger shaft was found to be very badly worn, hence all the problems. Is 200,000kms and 14 years a respectable life for a turbocharger?. What are the main causes of shaft wear? Thanking you for your efforts.

 

[Old.Tony]

A mechanic should not have taken that long to diagnose it - very likely the car just sat there while they did higher $ jobs. Nasty.

That's a good life for a turbocharger. They wear out more quickly if they're shut down when they're very hot (eg climb a hill, pull over at the top and just turn the engine off). If they're allowed to return to normal temps before shutting down this happens less. Towing also increases the strain on the motor and makes the turbo work harder, further shortening the life.

 

[Dustyfeet]

Restarting this thread, for information & interest of others.
It appears I purchased this Ute from mofo 2 months ago; fully aware it still has some faults. Slowly trying to solve them on weekends.
The main fault is the transmission is still in Failsafe mode (for another post) and minor issue is the engine still surges slightly above 2500rpm +/-100rpm, noticed bit of a pulsing feeling when driving, in engineering we’d call it “hunting”, can’t find a stable rpm.
I checked the computer, no ecu faults.
The computer showed mass flow and rpm were out of sync, strange.
Checked & cleaned the mass flow, no different.
Blanked ERG, no difference.
Disassembled foot pedal and cleaned contacts, in case signal fluctuations, no difference.
In frustration I thought, since it had a new turbo installed, maybe someone stuffed up, removed vacuum hose off turbo (boost valve) actuator. FIXED IT INSTANTLY.
So, realised that hose must have been installed on wrong output of the vacuum control solenoid down near AC compressor and swapped the hose, engine RPM now runs perfect.
So, while still not fixing the limp/failsafe issue with transmission, I’m disappointed in whoever installed turbo and happy I resolved one of the faults.

Will post on other forum re transmission, need ideas.