gday gday,

have been having a bit of trouble with my idle recently. shes been VERY tempremental and i cant figure it out.

couple weeks ago i basically did a full rebuild (head reconditioned, rings, sump, etc) and she's running beautifully :D, minus the idle problem which is:

Either of the following will happen at any given time.

a) idles fine, around 1200rpm (i turned up the idle a bit to try and fix the problem)

b) will idle very rough between 200 and 600rpm constantly dropping and rising. sometimes she'll just stall on me, this has happened when driving as well but ONLY when put into nuetral.

c) will drive, run and idle fine but when engaging neutral, the tacho will drop too close to 100rpm then hover around 500rpm.

d) occasionaly i have given her some gas and then backed off and put her in neutral and she'll just stall on me. starts everytime no worries but sometimes i have to give it some throttle to keep her alive

any help would be great, checked all vacuum lines, hoses, intake exhaust, everythin i can think of.

thanx in advance! tim:D

Sounds like the symptoms of Idle Speed Controller issues?
When was the last time you disconnected the battery? Or shorted something out? My experience (as to whether it's technically correct or not I dunno, but seems to work) is that if the ECU is reset, you can get these symptoms until it sorts itself out, especially if the base idle is set too low.
My thoughts are that the bouncing up and down in idle would appear, to me, to indicate that the ISC is attempting to do it's job. Failing anyone else coming up with brilliant ideas, here's what I'd do to attempt to sort it out:

- disconnect the battery for a while to reset the ECU again. This should (to my understanding) put it in a learning mode that'll fine-tune it's settings to suit how the car is driving.

- run it through a series of idle-learning procedures, to try to fast-track the learning in a safe environment (last thing you want is for it to die when going around a tight roundabout or turn). I've found a combination of the following to work, find yourself an empty piece of carpark or your driveway if you have a few meters to manouvre.
When idling, then turn on combinations of the aircon, lights, high-beam, brakes, spin the wheel back and forth to engage the power steering, basically put on as many different combinations of engine load as you can think of. Drive backwards and forwards a bit, getting some revs up then quickly dropping to neutral and braking heavily, whilst turning if possible.
If the engine keeps stalling during this, back off a bit and see if it handles it better. Basically push it as far as you can without actually stalling, and it should eventually start to respond better.

I've found the real killer (at least in a manual) is when you come into a roundabout or 90degree corner, engage the clutch and release the accelerator, stomp on the brake and turn heavily all at the same time, as it is the worst combination of the lot; rapidly falling revs to start with, brake booster kicking in, power steering kicking in, guaranteed to stall it at the worst possible moment. I had to learn how to keep my foot on the accelerator at the same time as braking and de-clutching, whilst blinking, turning, and hovering my hand over the keys in case I needed to restart on the fly...

hmmmm, a few good ideas there i will definately give a go.

i drained the power about a week ago and turned up the idle screw a tad to see if it made a difference. it did for a little while then went back to its old self.

i went out earlier tonight and it wouldnt stay alive unless i gave it some gas, i would crank it over, she'd start, sputter and stall. then coming home she ran beautifully, so im up chocolate creek without a popcicle stick atm.

i currently have no air con belt on but i cant see how that would make a difference?

she idled fine before the rebuild, im trying to think of what may have triggered this? could it be as simple as something not being plugged in correctly?

You have EFI, correct? Pretty sure the 4cyl EFI is similar to the V6 in that you have to bypass the ISC when you want to adjust the base idle, otherwise it tries to compensate for what you just did.
If you have the service manual, look for something like spark advance cutoff or something like that, you have to connect this with a jumper to earth, and it will bypass the ISC. I'm in a rush at the moment fixing my network, so can't look it up; will tomorrow if you have no luck.

from the repair manual it is section 13-2-4 and 13-2-5

diagnostic is on page 13-2-26

possible causes to stall and poor idle
the engine computer unit
the stepper motor (ISC)

we changed
the air flow meter so thats not the problem
TPS was adjusted

approx $75 for a ECU salisbury wrecking

Sounds like the ISC to me - its what our TS was doing until i replaced it. You can test the unit with a mulitmeter easily. You will see on the unit 2 rows of 3 pins. Test the resistance b/w a middle one and its nieghbour on each side. Same test b/w the other rows middle one and its adjacent pins. 4 tests all up. Cant remember what the resistance should be, but a failed ISC will show an open circut on one or more of the circuts tested as above.

easy peasy. I got a perfect and new looking ISC for $10 from a self serve wrecker :D