Suction Control Valves

[Benyars]

My triton has some serious surging issues.
The intercooler has been cleaned and flushed, Intake manifold has been removed and cleaned as well as the EGR.
What are peoples thoughts on the SCV? and is this the next place to look for these issues?

[MattE]

SCV is usually the problem from what I hear. If you have a scanguage or obd reader then look at the fuel rail pressure, if it is fluctuating by a few hundred PSI at idle and several thousand PSI while accelerating then its possibly the SCV.

If you haven't already, then do a search on this forum for "Surging" or something similar. There are quite a few posts on the topic.

[TimbosTriton]

I had an intermittent surging issue when I first got my ML, after reading all the posts on here (thanks guys) I decided the easiest and least expensive thing to look at first was to pull the SCV and polish the shuttle inside. Took me less than 20 minutes start to finish and cost nothing - it's never surged since.........
I bought a spare on eBay for $110 ($415 from the dealer) but haven't needed it yet.

[RHKTriton]

The tolerances are so fine on these things and it only takes a micro sized bit of muck to cause them to jamb.
Mine played up a couple of months ago for about a week and then suddenly came good.
So, sometimes the source of the problem either wears down or works it way through the valve.

Scanner will certainly show the consequent pressure fluctuations.

[paulmp]

They are extremely easy to pull off and check. I replaced mine recently with an ebay replacement, it was $110.

[desblaze]

I was having some serious surging issues over the past few weeks where is was almost becoming undrivable. But was intermittently no there on the odd occasion. I resigned myself to the fact that a manifold clean was in order and a new suction control valve. As I was about to do an oil change I also replaced the fuel filter. And bam, my problem was solved instantly. Crazy how the easiest thing to replace can be the problem.

[RHKTriton]

The high pressure pump's output depends on the available fuel input so a blocked filter will act the same as the scv throttling the input.

[RHKTriton]

Well the SCV finally had to come out for a look.

The engine was idling rough, stopping rough and just not sounding 'happy' after a service over the weekend, lube and filters.

The water warning light stayed on after fitting a new filter, so out it had to come again and free up the float.

On refitting, I suspect some contamination found its way into the SCV.

After giving the plunger a polish with fine valve bring paste and cleaning it and the valve cylinder the engine resumed normal operation.

[taxman74]

I replaced the SCV with a new one but still i get some surging at high rev above 100kmh. Think i will replace the fuel filter next.

[RHKTriton]

I usually buy a filter package which includes air, oil & fuel for a price that makes it economical to change all three at every oil change.

You could also check the MAP and MAF sensors just to make sure these are playing properly.

[Thongsbot3000]

I replaced the SCV with a new one but still i get some surging at high rev above 100kmh. Think i will replace the fuel filter next.

Could be carbon build up EGR/manifold. When last time you had it cleaned. Assuming no mods

[taxman74]

I replaced the SCV with a new one but still i get some surging at high rev above 100kmh. Think i will replace the fuel filter next.

Could be carbon build up EGR/manifold. When last time you had it cleaned. Assuming no mods

Well first thing last, It was surging badly when upping the revs or kickback though gears so i changed the air filter that was pretty dirty and that helped %90 cleaned the MAP and MAF that made no difference. Since it only surged in kickback high revs at around 100km or less on some hills i figger it must be the SCV.
So its replaced with a new one but still surging with kickback high revs, I have not had the manifold cleaned as i use a SPV thing on my airbox controler.
Would the surging throw a code if i had it checked out from a mechainic? I will replace the fuel filter myself before hand as i did get it in a kit with my oil filter and air filter.
Surely scan tool or scan guard should pick something up??????

[RHKTriton]

So from your latest post, I assume you're driving an auto.

That may now also bring the condition of the transmission fluid, lock up clutch and controls, etc, into play.

Another thought, the vane actuator on the turbo, sticking?

[taxman74]

So from your latest post, I assume you're driving an auto.

That may now also bring the condition of the transmission fluid, lock up clutch and controls, etc, into play.

Another thought, the vane actuator on the turbo, sticking?

Found the problem after all that, The SPVi (EGR Controller mod)was faulty - took it off and no more surging. Now I have to find out if I can send it back for a replacement.

[taxman74]

So from your latest post, I assume you're driving an auto.

That may now also bring the condition of the transmission fluid, lock up clutch and controls, etc, into play.

Another thought, the vane actuator on the turbo, sticking?

Found the problem after all that, The SPVi (EGR Controller mod)was faulty - took it off and no more surging. Now I have to find out if I can send it back for a replacement.

Now the surging is back, In the mornings i get the engine light coming on and she idles rough. Got me stumped.

[fez]

Hi All

Just wondering where you have bought the new SCV from.

[RHKTriton]

I got my last batch a few weeks ago off eBay - about $50 per unit. Typically should be able to get them under $180.

My ml is running much smoother and economy has improved, compared to the previous unit which got the polish job.

[Longranger1]

I got my last batch a few weeks ago off eBay - about $50 per unit. Typically should be able to get them under $180.

My ml is running much smoother and economy has improved, compared to the previous unit which got the polish job.

Did you do a relearn on the scv RHK?

[SLIMaxPower]

Doesn't 2T solve this issue ?

[Longranger1]

Doesn't 2T solve this issue ?

It seems to delay the need for replacement. Mine is still going at 130K kms.

[RHKTriton]

Don't need a relearn for a SCV replacement - its part of a closed loop, so ECU is actively adjusting it to set fuel delivery.

The polish treatment does extend the life for another 30 - 40%, but as I found, a new unit has the engine running more economically.

From my observations over 230k, there is gritty crap that occasionally finds its way into the valve and either causes it to bind or at least score the adjoining surfaces.

Polishing helps get the bits to work smoothly again, however the clearance has been increased and the minimum fuel that's delivered will always be a smidge more.


Re 2stroke; I've had occasions where the SCV was obviously binding (surging & poor acceleration) this lasting up to a over 100km and the suddenly coming good again.

When this starts happening, I realise I haven't added 2T for a while. Give it a dose and the problem either doesn't get worse or clears up more quickly.

When I'm on top of it, adding a couple of hundred ml every tank or second tank seems to prevent any SCV symptoms. Two possible factors at play, extra lube and/or cleaning additives in the 2T.

Finally, if you do the polishing routine, just make sure that all the valve bits are super clean before reassembly, inc your hands and tools. You don't want any grit from the paper getting into the pump or injectors.

[luckey]

ML 3.2 4M41, auto, MY09 142,000km. I'm getting symptoms that seem like a SCV problem - mainly intermittent power loss at 2500-3000 rpm. Have had recent ECU tune - normally tons of power & torque, so it's really noticeable when it drops away. Have changed fuel & air filters and had manifold cleaned, EGR now deleted with the ECU tune. The check engine light has not come on at all - could this be a SCV issue, and not lighting the CEL? Any advice welcome, cheers

[chapmaan]

For what it's worth I had surging and a hesitation at low revs (MQ manual). Before I had a chance to book a visit the dreaded DPF light started flashing, however there was a period when the surging occurred without a DPF error. Turns out my DPF sensor had gone and there was some talk about a modified version with a longer wire - apparently movement can upset the original.

Got a new DPF sensor and all is well. Apparently the bad sensor was causing all sorts of confusion with injecting fuel to manage the DPF - hence the surging.

I'm not as mechanically minded as I once was so can only take the above with a grain of salt.

[SLIMaxPower]

Purchased a scv from ebay but seems to be the wrong size... Doh

Sent from my SM-G935V using Tapatalk

[RHKTriton]

Hi Sli'

There are two models on the Tritons, a shorter unit and a longer one. Don't know if they interchangeable, but if everything from the face of the flange is the same, it may work. Might be worth checking its coil resistance with a meter to compare if they're the same also.

Interestingly, my ml & son's mn use the same unit ( shorter version).