my car is doing weird things please help me

[sutto]

having trouble with my vr calais. a few times it has just stalled while driving and was hard to start a few times like it had a flat battery but when i called the racq guy out he told me that my alternator was no good. I had a mechanic check it with his multimeter but it was all good. the car will start every time but runs rough and will stall at times. when i turn on the key to just red lights i can hear the fuel pump start up and when the car is idling and i rev it up to over 2 on the tacho i can hear an audible sound but see no lights on the dash.
I have been told it could be the injectors,coil pack or fuel pump.
not sure what to do can someone please offer some advice.

[Wombles]

Maybe check codes first?
Try changing the fuel filter as well as that could be blocked and restricting fuel flow..
When you fill up with fuel, put some injector cleaner through it to see if that helps?
Have you checked the voltage from your battery as well?

[hako]

Sounds like the Crank Angle Sensor (CAS)....checking the codes may verify.Checking error codes VR/VS (Revised)

[sutto]

Thanks for that but if it is the CAS how do i replace it

[hako]

Put simply you remove the harmonic balancer with a large socket and a puller and the CAS is screwed to the front of the front cover. It's not a big job and most mechs will charge less than $100 for labour - CAS is about $40 - $50. Lots of people change their own if they have the tools.

[sutto]

Hi Hako, Thanks for the advice so far.I have checked the error codes and it gives me a 12 and when I turn the key to reds only i can hear the fuel pump start so maybe it might be blocked or dirty injectors i have run the tank on empty a few times so i am going to try some injector cleaner see if that works. but thanks heaps for your help.

[hako]

It may pay to check your battery as Commodores need a fully charged battery otherwise they can have trouble starting. Easiest check is to have the headlights on when cranking - if they dim badly you can bet that the battery has reduced capacity and cannot keep the volts up when cranking. Also if it is over 2 or 3 years old then it's due for replacement. Also you need clean tight battery terminals.
If you have a charger try charging the battery overnight and see if it starts better in the morning. Another check is to inspect the connector at the back of the alternator where the big cable connects with a nut - the wires inside the cable have a habit of crystalising and breaking due to heat/age and the result is that the alternator cannot charge. Just eyeball the insulation at the connection and try and move it a bit.
Finally - when doing the codes you wait for 3 lots of 12's, then the fault codes are given (if any).