Intermittant rough idle/rpm drop

[Smokey5159]

Hi guys,
I've tried to see if my issue has surfaced here - but I'm not sure it has.
I have a 2011 MN Triton that has done a little over 200k, and I have
noticed of late that every now and then when at idle, the idle seems to lower,
or run slightly rough - then disappear as soon as I blip the throttle,
or move away from the lights. I regularly change the fuel filter (every 5k) - and
haven't used any fuel additive for quite a while.
Does anyone have any clues as to what may cause this..?

[Longranger1]

When we're the valve clearances last done?

[Smokey5159]

Hi there,
I'm not sure actually...
Would that not be a consistent issue if it were valve timings?
Tonight on the way home from work (45 minutes) there were no
instances...
Cheers Paul

[coughy]

200,000 km i would be looking at the inlet manifold and scv first
get some cleaner from bitsaremissing stealer it works ok

[Smokey5159]

Hi there,
Yep - inlet manifold was cleaned 12 months ago. ..
Not sure what the SCV is, and are you saying Mitsi
Dealers have a cleaner that you can buy?
Cheers!

[OffRoadDave]

My first guess would be SCV (suction control valve) as well, my my15 does exactly the same thing with 45k on the clock when I use Caltex fuel, if I stick to BP it doesn't do it, dealer seems none too interested unless I can show them doing it in front of them so I put up with it.

When checking the fuel rail pressure with my scan gauge when it occurs, the rail pressure rises to 3 times higher than what it usually sits at while idling, I assume it's putting extra load on the engine causing the lower revs/running rough, and like you as soon as I touch the throttle it comes good.

[RHKTriton]

SCV is the likely culprit, only takes a few bits of microscopic grit to jam up the plunger.

I tried the Mitsi cleaner and it performed no different to any of the regular cleaners. Looks and smells the same, essentially a naptha based cleaner.

If you find that your unit runs fine on BP & not so great on Caltex ( suggests contaminated tanks at Caltex), stick with your BP. In our area I've found the Woolies Caltex has provided the best run.

When ever I get any SCV symptoms, a shot of 2stroke fixes her up in a couple of days.

[Smokey5159]

Thanks guys..!
I've just been loaned a scan tool by my
airport mechanic mate. He works on a lot of diesel
vehicles, including the earlier Mitsi Tritons. He
also suggests the SCV is a problem and a check of the rail pressures
etc.
I'll look at all of this in the next couple of days.
Cheers Paul.