Another Idle Issue

[benny_bobo]

I have a R33 Series 2 Auto, runs fine when cold. Drives fine when warm, but won't idle properly. It will idle at about 700rpm when warm, then it will start dropping to 500rpm and raising to 1000rpm (in Neutral, Park & Drive)

The boost gauge shows vacuum (not boost) pulsing between 10 and 20 with the revs playing up. Exhaust note goes deep, runs rich. When the lights are on when its warm it is worse and blows smoke.

I've cleaned the AAC, checked the TPS, adjusted idle stop & idle screw etc..

Car stalls when I disconnect the AFM.

It runs better when I remove the boost gauge hose off the back of the manifold (letting in more air).

Idle stabilized (but lowered to about 400-500rpm) when I disconnected the AAC plug, but now when I do that it stalls.

I've checked for leaks, spraying air hose joins with carby cleaner.

I've tried banging the ecu with my hand, and it doesn't do anything.

I'm thinking the car stalling when disconnecting the afm has something to do with it...

[benny_bobo]

and i just got 275km to the tank.. Its a stock skyline too.

[DVS JEZ]

check for vaccuum leaks, check all intake piping, cooler piping, vaccuum hoses etc etc etc.

[The Dan]

+1 as above but also check/clean your AFM

[benny_bobo]

What should afm voltage be on idle?

[benny_bobo]

mine is 1.25v at idle.

Worked out why car wouldn't run without afm..

I remembered that about a year ago, the car wouldn't start, spliced the afm ground wire to the battery and the car would run fine.

If i disconnect that and just use the ecu afm ground, it wont start.. but if i disconnect the afm AND the negetive ground to the battery, it will run.

Idle isnt perfect without afm, but im guessing it would run rich without afm?

[paulr33]

disconnect battery terminal in the boot

press brake pedal a few times (drain all power)

then reconnect battery terminal

start car and let it idle

the stock ecu will perform base idle adjust and should be ok from here on

[benny_bobo]

reset the ecu already a few times... doesnt help.

and btw, its a s2 sedan... so battery under bonnet.

[benny_bobo]

seems to only happen with lights on now.

also, turning the steering wheel at idle does not raise revs (idle up), but the ac does. Don't know if that is related at all?

[benny_bobo]

runs better with air-con switch on (idle up) when the lights are on (no air-con belt though)

[wasnt me]

see is you can get your hands on another ecu and try that, i had the same problem and tried every thing only went away when i got a new ecu.... its worth a try.

[benny_bobo]

So I disconnect the O2 sensor and idle stabilises after about 10 secs... let it run for 5 mins all good. connected O2 sensor again, starts hunting... thought it doesn't use O2 at idle?

Or does the ecu think it isnt at idle? check idle sensor? guess I just answered my own question...

[benny_bobo]

dont know what im doing with the multimeter on what i think is ohms, on top connector pins 1 & 2, throttle closed = 0, throttle open = 1.

[honan]

had an issue IDENTICAL to this, checked everything you have.

turned out to be the rubber o-ring/gasket between the top and bottom half of the intake manifold (between chamber and runners) shit of a job to take off but fixed the issue straight away.

may not be your issue but worth a shot.