Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community


Ignition Coils/Module


Jul 5, 2006
Reaction score
Members Ride
2000 VX Calais 3.8L Supercharged
After having many troubles of shitty idle after starting the car up of a morning, and mostly after its been sitting for a long time ive finally got around to doing something about it.

Problem: After first turning over it will sorta fart/splutter as if its sorta chokeing on something and spitting it out. If the car actually manages to not stall(which it tends to do 2/3 times) it will go up to about 1500rpm and come down to about 2-300rpm and rock and roll pretty badly. It then proceedes to go up and down in the range of 300-1500rpm where it will almost get to the point where it will stall at as its jumping around 300rpm. I will have to sit on my accellerator to keep the revvs up, after keeping the idle up after about 30secs or so ill take off and after about 5mins of driving (by the time i get to work) the car will still be quite cold(just under the quarter mark) but it wont be jumping all over the place with the idle.

So far ive done the following
Cleaned IAC + Throttle Body
New iridium ix NGK plugs
New Topgun max300 8mm leads
Changed oil to 10-30w full synth mobil1
Replaced CAS sensor as was feeding out error 46/47 a few weeks ago IIRC
(fuel filter to come soon)

Progress: After changing over the CAS sensor, the car has actually seemed to start up on a better ratio and is no longer spitting out code 46/47. The car will usually start up after about 2-3 goes of cranking for a few seconds (with the aid of accel to keep the revvs up after its turned over). But the problem of the car actually idleing properly without the aid of my right foot is still existing.

I have talked to an autoelec and just by what i told him he has told me its his best bet its an immobiliser related problem. So i looked in a few manuals (gregories+hains) the one 1 to test if the immobiliser stuffing around the starting ect. is a big stuff around waiting 2hrs with ur key in the ignition ect. So rather than doing that yet ive tested the rest of the ignition system.

The coil's are sposed to be within 5000-7000 ohms, and the module is sposed to be within 0.3-1.5 ohms. The coil's all read 6000~, but the module read 0.32 - 0.34 across them. Even within the threshold of the acceptable level, its JUST sitting on the boarder.

Would it be worth replacing the module under the coils?
Could it be a blocked cat converter?
Could it be a stuffed ECU?
Ive done a bit of searching on this topic, but nothing has really surely solved the problem.

Anyone got any prices of working 2nd hand parts?


Well-Known Member
Jun 30, 2005
Reaction score
Eschol Park, Sydney
Members Ride
WH II Caprice, 5.7 2018 Equinox LTZ V
I'd be looking at the IAC valve because it controls the idling. I doubt if the immobilizer would give you a problem with idling.