STX 550 power pause on throttle.

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Jan 12, 2022
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Hi guys, I'm new on this forum, first post!

I have a 2014 Navara stx-550 (V6 diesel). I love ths power of this thing.

I've noticed recently every now and then when I put my foot down there is a sudden drop in power (might last a second or less) then the it recovers as normal.

This is beginning to worry me, usually the sign of something slowly failing but I don't know what this might be but it seems like it might be electrical, might be wrong.

No idea where to begin to look.

Any ideas?




Staff member
Oct 3, 2009
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Mid Coast Region, NSW, Australia
There could be several different causes for this. The best way forward is to analyse the ECU's data for the throttle position, fuel rail pressure, boost pressure and engine RPM. An android app like Torque can do this (logging feature, stores data in .CSV format for use in a spreadsheet). This would then give you some idea of where to look for without spending money on changing components.

Possible causes:

* Turbocharger control system fault. I'd have thought the 2014 550 would have an electronic turbocharger actuator and Nissan replaced some of those (predominantly on the 2.5s) but that doesn't preclude a fault on the 550. If it's vacuum controlled, you may just be losing some vacuum around a joint that's starting to harden or crack.

* Fuel pump - on the 4-cylinder engines we often see problems with the SCV which suffers from tarnishing, and is sometimes rectified by simply running a bottle of injector cleaner through a tank of fuel. It's particularly noticeable as an "unsteady" idle, where it seems to surge regularly (like the engine is "hunting" ). Doing this with a good cleaner (Liqui Moly Fuel System Treatment is my usual go-to) will cost you about $20 and cannot hurt regardless.

* Boost leaks/hose expansion. Now this isn't common any more, because most of the people who had this issue have already replaced the hoses, but there were some hoses that went out that expanded under load - remember that once the turbocharger has compressed the air, it's sitting at around 20psi+ and somewhere north of 200 degrees celcius. If the hoses balloon, you'll get signficant lag until the hose stops ballooning. There were also some STX550s that had issues with the intercooler input tank expanding - this is easily checked by visual inspection.

Other systems can impact it - faulty EGR valve, faulty throttle body, leaking EGR tube ... let's start with the above and see what comes of it.