Can I pick your brain?

[coolusername]

Hi, I've got an issue with my '02 ST-R with a VG30E engine, I know the majority here are running diesels but I'm hoping someone may help to point me in the right direction.
The problem is that she won't hold rev's at idle while in neutral, fluctuates between 5/8's of f a and 600ish, if I put her into any gear, clutch in, rev's go to 1500 give or take. The NPS, air filter and fuel filter are all new, fuel filter being changed out today. I have run some injector cleaner thru her this week (currant tank of fuel, almost on empty) and am wondering if this has caused an injector problem to arise or that maybe the afm is on it's way out (I've pulled it out and given it a good clean). I had the same kind of rev's problem with my wrx, changed the afm, and problem solved, but before spending the $ I thought I'd ask around first in case someone else can share some wisdom.
Thanks in advance, rock on

 

[AutoTrust]

Check and clean your throttle body and IAC Valve (idle air control). That has been the problem on other Nissans running the same or similar engine.

 

[Dave]

Personally I reckon its the Air Flow Metre.

Seen a few V6 TF Rodeo's do the same thing.

Check the voltages coming out of the AFM.

Got a service manual ?

 

[coolusername]

I pulled the IAC valve today and gave it a clean, no chance to go for a run until tomorrow tho, when I'l get some fresh petrol. I have got a copy of the service manual, might have to invest in a volt meter to check things out.

Cheers Dave and Auto Trust.

 

[coolusername]

So today I cleaned the throttle body, ran a foaming cleaner through the intake manifold, kind of helped a bit, idles around 500ppm in neutral and 800ish when in gear. I also got myself a volt meter to check the afm. The output voltage from the afm is meant to be between 1.0 - 1.7 at idle but i couldn't find any reference to the color code for the wire to check so I checked them all and this is what I got : 4 wires blk/w : 3.21 (earth?) r/w : 12.81 (power supply?) g : 1.6 (output voltage?) b : 0. If someone could clarify that the output voltage is the green wire I'd be grateful. Wondering if the black/white wire is an earth and if it should be reading 3.21v.
Also noticed a shudder/ loss of power while driving to the servo for a fresh tank today

 

[Dave]

Hit Raywise up.

He is on here a fair bit, but he has the VG33E.

Worth a try.

 

[raywise]

I sent you a reply Jeff, but yeah, the first thing I thought of was the Idle Control Valve which sounds like you have already looked at. Infiniti Idle Control Valve Replacement

The symptoms of a faulty one as described in the link above sound fairly similar to what you are experiencing. This thread rpm surge at iddle sounds like its going to die but wont - Nissan Frontier / Navara Forum also hints at the idle valve, these things can be so frustrating to sort out..........

I haven't had this prob yet so I can't give you a solution, sorry.

 

[Dave]

Ray do you have a multimetre ?

Could you check the voltages on the AFM.

 

[raywise]

The earliest I can do this would be tomorrow Dave, at work and have a function tonight. I'll do some measurements and post up tomorrow morn,

 

[Dave]

Its up to you Ray, there aren't many of you V6 guys around.

I am sure the bloke will appreciate it.

Another busy busy day.

Oh and I get to approve new members now. Just helping Dylan out abit more.

 

[coolusername]

Cheers for your help Ray and dave, when i get home from work (FIFO) I'l go through the diagnostic procedure for the IACV that is in the service manual and see if I have any luck. If not I may just have to suck it up and find a good worksop in Perth and put abit of trust in them.

 

[coolusername]

Seems my new nps could be the source of the problem, disconnected it on a whim, vast improvement when I took her for a quick spin round the block. I'l see how she goes on a longer drive later this arvo.

 

[Dave]

How'd you go ?

Never heard of that NPS problem in the V6's.

Suppose there's a first for everything.

 

[coolusername]

She definitely ran a lot better, rev's stayed constant when in gear, clutch in. Not surging to 1500ish like before. The engine shudder/jerking around 2500rpm has all but disappeared. I pulled the IACV out again and hooked it up to a 12v supply and it was working fine. Away at work now so I'm going to see if I can find anything of use in the service manual to help check out the NPS when I'm home next.
Any other ideas/wisdom is much appreciated!

 

[LLadnar]

Mine was just starting too do the same thing when I sold it, must be a common fault with them.

 

[coolusername]

Hopefully it is a common thing that some one has gone through and can pass on some knowledge. Want to get this sorted.