I've got a series 2 AU XR6 VCT that has had problems with the VCT unit in the past, and quite possibly has some more again right now... Just wondering if anyone can give me a bit more information on how exactly they work? And describe any common faults they have?
Thanks...

can you explain the faults you're having ? Usually these units have more crank sensor problems then vct problems. With most vct engines though they must have pretty clean fresh oil at all times. Perhaps the unit itself just needs a good cleanout ?
how many km's ? Mines got nearly 250,000 hard km's on it and it's still running standard gear and works fine touch wood...
The entire assembly consists of the vct unit (with matching head),a different camshaft,oil feed and a solenoid as far as I know. I think there is only two timing settings with au vct, not like B series.
Maybe the oil feed is insufficient ? Maybe sensor problems ? Maybe there is prior unknown mechanical damage ? Too hard to speculate.

Bottom line is anyone would need more information to solve you're problem.

Well I desperately need an oil change, and I'm told that the AUII vct's are notorious for having a valve cease up on them due to unclean/old oil. At the moment, it idles with a bit of a subtle misfire once every 2-3seconds and when it revs beyond 3500/4000 rpm it misfires as well...
Also, I am told that there is a filter in the VCT that easily clogs up. Is that easy to wash/change/inspect?
If it is ceased, can it be replaced/fixed or is it a case of sourcing a replacement VCT?
My mechanic said he wouldn't touch them, and is hoping the problem goes away with fresh oil... So I imagine they are a bit of a pain in the a**.

I know the BA's had a problem with vct filters clogging so in the BF they removed them.... this approach is fine as long as the oil is kept clean. The AU, I can't say, I don't know enough about. Same approach with all late model motors though, change the frikin oil. Expensive oil is usually cheaper than a reco or an engine swap.

The missfire could be attributed to the crank angle sensor but again I don't know enough about them. Never had a problem with them.

Lastly I would advise a new mechanic if he won't touch your cam gear. I guess he knows more than me though ?

Yeah, I spend good money on my oil... I have the same opinion as you on that. But have been having lots of trouble with my car lately, and I guess I just missed the fact that the oil really needed changing... :/

I will check it out, thanks for the heads up...

Well he is a good basics mechanic... Though he drives and owns a drag team in his spare time lol. I want to get the car to have a good once over by more of a performance minded mechanic, but just don't know where to go to get it done...

I find theres usually 3 types of mechanics around these days, theres the oldskool type that could tune a carb'd car to run hardher than most could imagine. Then theres the newskool mechanic that's all up to date with all the computer related technical stuff,tuning etc. And theres those who dabble in both.

Most Oldskool Mechanics & Newskool mechanics are awesome at what they do (hopefully) but don't interchange much. The dabbler is sort of out there in the middle. I've heard it's pretty expensive to be up to date with most late model cars on the road. Expensive courses & equipment.

If you can cover the basics yourself it will always cost you less.

So what other problems has it been having ? Mines had the usual 200,000km problems, nothing major. Needs some new bushes etc but aren't critical.

there is no filter in the vct unit, the vct unit advances the cam timing from idle to 3000rpm then it returns the cam timing to its stationary position untill the rpm drops under 3000 rpm.
ive ran a vct engine with and without the vct connected, disconected it only effected the down low performance.. it had no effect on idle or drivability quality..
i would say you missfire is more ignition lead or coil pack related..

no filter? i was told that the AU VCT's had filters, and they commonly clogged up so they removed them for the BA units... or maybe i have that the wrong way around...

hmm well the way that you describe the VCT, it sounds like that isnt my problem... which in a way is a good thing, but it means that i still dont know what exactly is wrong with my ute.

i went to see my mechanic again today, and he suggested a couple of things:
blocked exhaust - though i went to see the guy that did all my exhaust work (Men @ Work Exhaust - Capalaba) and we came to the conclusion that a 2.5" straight through muffler could not be clogged up by a failing cat.
coolant sensor - we viewed the output from the sensor and it was putting out some odd figures. at random intervals (up to 5 min gaps) the senor would peak/drop 90 degrees, so that could be a cause to some of the problems.
faulty computer (to tired to think of the right name... the one inside the passenger kick panel) - the mechanic noted that he thinks there is a physical fault with the computer, i think it may have something to do with the water that leaks into the foot well... hmmm... :/

its not the leads/coil, i have only just got new leads, sparks, coil... serviced injectors/rail, new tiger headers, high flow metal cat, and sports flow muffler... so yeah... got a few things checked off for what it isnt...

yeah my mechanic, well this is what i have noticed, is a very methodical man. he likes to tackle things one idea/problem at a time and they re-evaluate the car after each step... well conected and very good at his job... but cause of his methodical approach to fixing cars, it tends to take some time... although he definately gets things do (and done right, so far)... so yeah pretty good i guess. also doesnt mind doing things last minute/over the weekend etc which is EXTREMELY handy...

I think I may be suffering the same issue on my 02
AUII XR6 VCT Ute.

Although if a cruise up to a set of traffic lights at random times the ute will just die in the a***, sort of misfire then run outa revs and die, if I start again sometimes the problem clears itself or other it'll misfire and die again, when this happens the open way to keep her running is to rev her up a bit until the light turns green, seem to drive fine until the in neutral or the revs get low.

I've replaced the Plugs, Leads, Coil Pack and the Crank Angle Sensor.

Really getting sick of it and I think the mechanic is all outta ideas.

Has anyone had this problem or similiar and had it fix / no what the issue is.

Cheers