Rough Idle and miss firing

[HSVenforcer]

Gday all,
I got a VS V6 and lately it has developed a rough idle.

- It only does it when at operating temp
- When driving it runs fine, only plays up at idle. Putting in reverse almost causes a stall.
- If i turn on the rear demister or air con it goes back to a smooth idle

I am suspecting either water temp sensor (though was replaced about 20,000km ago), CDI packs or computer.

I plan on using my mums VS for test parts but was wondering if there is anything else i should be looking for whilst i have things in pieces. Also if anyone could point me to somewhere which has the ohms values for the water temp sensor i would greatly appreciate it as well.

Thanks
Steve

 

[holden#1]

a bit of a wildcard, but have you checked the plugs?

 

[HSVenforcer]

Just did a service on it (it was rough before as well), did plugs, filters, oil and both O2 sensors (they were somewhat overdue)

 

[fitzy2005]

have you tried cleaning the throttle body? and checking for error codes?

 

[HSVenforcer]

I have not checked throttle body yet. Didnt give it a thought since its alright cold and when i am driving. But i shall check. There are no error codes showing.

 

[protossw]

Check fault code first.

Could be crank angle sensor.

 

[yyg998vsute]

Mine to has a rough Idle

not as rough anymore

but Ive now changed the all 3 coil packs, crank angle sensor, Harmonic, pulled the throttle body and the plenum along with the injectors of

Cleaned the throttle body and plenum cover absolutely full of black stuff,
thick Carbon

Clean as a whistle now, and starts and goes better too,

 

[veclubby]

tried new leads mate?

 

[SlyVR]

mine was running crap, i got a new coil pack and plate seems to be fine now
check leads
plugs (and gap em correctly)
coil pack
IAC


thats where id be looking

 

[sircruisealotVS]

the water temp sensor wouldnt affect it like that, if that was playing up it wouldnt cold start properly (you said its fine other than at operating temp).
im also slightly confused...the title of the thread says that its missing...but you only mention a rough idle. so does it miss as well? if so when does this happen?
the fact that you say it goes back to a smooth idle when you put the aircon on makes me think it has something to do with the IAC valve. when the aircon is turned on the idle will rise to compensate for the extra pulley the engine has to run for the aircon compressor...so this rise in idle would appear to smooth out any roughness.
as a starting point which wont cost you anything but your time, take off the throttle body, remove the IAC valve and clean it up with carby cleaner. spray some contact cleaner or wd40 into the spring area of the IAC and check to see it has movement. also give your throttle body a clean up and clear out all the gunk in the air ports that run up to the IAC recess.