What Would Make An Rb25 Idle Hunt?

[copycutter]

Just wanting some ideas on what would make an rb25 idle move around a bit when sitting in traffic, and the car stall after driving for a bit when i use the clutch.

I'm finding myself having to 'catch' the revs as they just drop straight down if i don't heel and toe when braking, so it's pretty annoying.

Cheers,

[RANDY]

Usually the stalling is an atmospheric blow-off valve. I found a stock one and whacked that on, no stalling when slowing to a stop with the clutch in.

The hunt... I have heard that the idle air valve towards the back of the inlet manifold (plenum) is the cause of this. It may need to be removed and blasted clean with contact cleaner or carby cleaner.

I hope that helps!

[copycutter]

I have no BOV currently so not sure if the compressor surge has anything to do with passing air back across the AFM and causing over-richness and therefore stalling. However, this can occur when i'm cruising off boost or on full power then backing off.

The IAC is a grey area for me. I have been told in the past that this thing needs to be set at a correct level or 'calibrated' to work correctly. True/False?

Also, the screw at the back of the unit that controls the idle on this valve, what sould I do, set it at about 700rpm on idle when warm?

[fEkuaR]

completely unrelated to the problem just followed your link to the write up on yours and your mates car. Loved it... was a great read. Hope you get your issue sorted i have had similiar issues with my 25. I was wondering if it was the airflow meter or IAC myself.

[Kaido_RR]

i had a similar problem :S

change my coilpacks from stock to splitfire fix the problem

[copycutter]

completely unrelated to the problem just followed your link to the write up on yours and your mates car. Loved it... was a great read. Hope you get your issue sorted i have had similiar issues with my 25. I was wondering if it was the airflow meter or IAC myself.

Thanks dude. It's taken a long time just to get the cars to where they are now, and we both still got a heap of money to spend still..

My cars only just finally producing power after we realised the car had a massive boost leak, an rb20 crank angle sensor (no vvt ), wrong sparks, coils needed looking at etc etc.

Now that the AFR's aren't rich off the richter without the boost leak the clutch is slipping like crazy

When it does hook up in 2nd it burns all the way through the gear sideways when it comes on boost --> only 7 pound too!

' date='24 Apr 2006, 02:09 AM' post='2111627']

i had a similar problem :S

change my coilpacks from stock to splitfire fix the problem

I think my coils are in pretty good nick, and i dont really have the spare 600 to get some splitfires. read: clutch....

If my IAC line had a slight kink in it when it bends to come up through the inlet runners and into the IAC have any effect on the way the car idles and stalls?

[Guilt-Toy]

Hey mate.

I think i know the problem.

Do you have a big turbo on the car?

Do you have the AFM so close to the turbo ?

Do you have a big AFM ?

Please give info on ALL mods to car.

Does it blow lots of smoke when it happens ?

please advise

[copycutter]

Nah sorry mate its got a stock turbo, and an r34 AFM - which im pretty sure is identical to my s2 r33 one on the floor in the passenger seat

Still pretty much stock atm besides cat-back, the ic, filter and the plenum.

[copycutter]

Edited April 24, 2006 by tuna_144

[R31Nismoid]

I have no BOV currently

This is the problem

put the stock one back on, problem goes away

[copycutter]

dont have a stock one anymore.... different intake tract

and an atmo one would probably make it worse, huh?

[Guilt-Toy]

dont have a stock one anymore.... different intake tract

and an atmo one would probably make it worse, huh?

try changing the AFM ??

[R31Nismoid]

dont have a stock one anymore.... different intake tract

and an atmo one would probably make it worse, huh?

probably much the same

Plumb-back however would fix it

[RB30-POWER]

First thing first,

-Make sure there is no vacuum leaks

-Make sure the plugs are gapped correctly and not fouled

-Make sure the ignition timing is set to 15deg btdc @ 650rpm

-Make sure the TPS is adjusted for idle position (0.4-0.5Volts @ idle)

-Make sure the base idle is set correctly.

To do this you have to make sure the engine is at operating temp & all electrical loads such as lights, AC etc are turned off

Then remove the TPS connector (this will set AAC valve opening to a set opening i.e no feedback or change to idle rpm)

You now need to adjust the screw on the idle adjusment assembly so that the engine revs are approx 650rpm (+ or - 50RPM)

Then reconnect the TPS and the base idle is set correctly.

[RB30-POWER]

Of course all the above assumes you are still running standard engine managment?

[copycutter]

Thank you for the list rb30, that was exactly what i needed to go over with - a checklist.

Yes i am running standard computer for the time being..

How exactly do i test the TPS?

Oh yes, and plugs have been changed about 250kms ago. And the timing has been reset recently because all this time i had an RB20 one!!!

So now that i have my rb25 one with vvt, obviously it had to be reset - was done at Desynz where the other stuff was fixed.

All my past misfiring problems have gone since he serviced the coils and put in his own type of copper NGK plugs (Re6 something or other)

I've put in BCPR5ES11's and they sucked balls, and then BCPR7ES-8, and the problems still wasnt fixed with the decreased gap.

Its now smooth all the way to redline tho.

Edited April 24, 2006 by tuna_144

[Craved]

def check for leaks with the plazmaman plenum.. im still trying to sort mine out, something between the plenum and std runners is leaking, even with new nissan gasket.

mines very touchy when idling too.

[insu]

There has been much debate as to what exactly it is that causes the RB series motors to hunt at idle, the solutions/problems I have come across in my reading include:

1) Dirty/ Faulty AFM

2) Vacuum Leak

3) Dirty/non functioning AAC valve

4) Dirty/non functioning idle bypass screw, which is part of the AAC assembly

5) Faulty O2 sensor

4) Faulty Spark (be it coils or plugs or both)

5) Faulty cold start idle assembly

6) Faulty water temperature sensor (which can apparently open and close the AAC to compensate for the cold start valve, this is just hersay thou)

7) Non standard BOV leaking to atmosphere

8) Faulty strength of signal being sent from computer to activate idle setting on fuel pum (ie under fueling engine)

9) Faulty TPS setting or signal output

10) Dirty or sticking throttle body.

11) Bad seal or no seal to top of motor (ie, oil filer cap not closed or broken etc)

Pretty much everyone of these items I can think of have been blamed for bad idle/ Hunt, and each person seems to have their own results with fixing various items.

Personally I ran DIY on cleaning your AAC valve assembly, and it seemed to have fixed my problem, but judging by the amount of problems and potential fixes, i am unsure if this will help you. Btw its in the DIY section if you want it.

What we need is to all get together in a workshop with a couple of skylines with this problem and work on them until we find the faults for sure and document the process.

You never know we may single handedly find the biggest eluding problem to skyline drivers known to SAU!

Edited April 24, 2006 by insu

[RB30-POWER]

Im not familiar with the plazmaman plenum physically, but before it was bolted up did you put a straight edge over the plenum base where it bolts to the runners to make sure its perfectly flat.

I know on some plenums when they are welded the base warps and if the base isn't machined perfectly flat, it will never seal, even with a gasket.

I doubt this is the issue with such a nice plenum, however some things need be checked when looking for those illusive bugs and gremlins.

I will have a look in the manual for what pin number the TPS wires are a little later tuna_144.

[copycutter]

def check for leaks with the plazmaman plenum.. im still trying to sort mine out, something between the plenum and std runners is leaking, even with new nissan gasket.

mines very touchy when idling too.

whats the best way to see if the plenum's leaking? carby cleaner?

Oh and thank you insu, excellent list of things to attack.. Thanks for taking the time to type. I'll base my further questions after looking this over after one sometime

Edited April 24, 2006 by tuna_144