Adjusting The Vct

[Branelly]

Ok so after screwing around trying to get the engine started for hours we eventually decided to check the timing belt. And as soon as we took off the cam gear cover we saw the problem. The bracket that holds the VCT unit had snapped clean off. Would not have a clue how this happened. So anyway my friend had a spare bracket that we bolted up but now we have another problem.

In side the cam gear there is a semi circle that is meant to line up with the semi circle in the vct unit. But the one in the cam gear has broken off. Meaning that the vct unit can go into the gear in any number of degrees. The problem being that we cant align it.

Good thing is we have managed to start the car but it doesnt sound right at all. Under acceleration it sounds like a diesel truck.

Any ideas, im guessing the only way to get it right is trial and error trying to align the vct unit or buying a new cam gear that still has the semi circle intact.

[Don Dada]

Thats not the vct unit bro....its the cam angle sensor CAS

http://www.skylinesaustralia.com/forums/topic/232550-cam-key-for-cas-broken-urgent/page__p__4081411__hl__cas+key__fromsearch__1#entry4081411

http://www.skylinesaustralia.com/forums/topic/356269-castimming-issue/page__p__5701524__hl__cas+key__fromsearch__1#entry5701524

[PM-R33]

Yep you are talking about the CAS.

You will need a replacement CAS, no other way to fix it.

Your ECU will have no idea on which cylinder to fire and your timing will be all over the place. DO NOT DRIVE THE CAR.

[Branelly]

Whoops yeah i knew it was cas, just for some reason had vct stuck in my head. Anyway as it says in that first topic if the cas is one tooth out it wont fire. My car is definitley firing so it must be in the right tooth. Now i just have to adjust it untill it runs right.

Now i have another question but it might not be related. My boost gauge is reading about -5 to 0 psi on idle. Its varying so much because of the idle being spaz which i think is the blow off valve not haveing the return pipe on it right now. If i remember correctly the boost should read about -20 on idle. Could this be timing related or is it more likely to be vacume leak or boost leak. Ive already tried pulling the vacume line off the blow off valve so it doesnt open but it doesnt seem to to make a difference to the idle. The hole in the intake for the blow off valve return is also blocked.

I spose it could be related to the timing but its hard to tell at this point.

[Don Dada]

You will need a replacement CAS, no other way to fix it.

????.....no he wont

The key is broken off on the cam so if its anything he would have to replace is the exh cam not the cas

Edited April 8, 2011 by Don Dada

[PM-R33]

Oh sorry you are right. He said "the one in the cam gear" and obviously there is no semi circle in the cam gear so I assumed he ment inside the CAS. But yeah he ment the one in the camshaft.

However, if the bracket for the CAS has broken there would be a high chance that the CAS it self is f**ked or on it's way to being.

[Branelly]

However, if the bracket for the CAS has broken there would be a high chance that the CAS it self is f**ked or on it's way to being.

Broken in what way? Visually it looks fine all the teeth are good, spins fine etc. Rotating it on the car does affect timing but is it possibe that its getting the wrong reading some how?

[PM-R33]

Well think of it this way.

The bracket is bolted onto the head. The CAS is bolted onto this bracket by three bolts. The spindle from the CAS simply sits inside the exhaust cam and free spins as the camshaft rotates. Inside the CAS bolted to the shaft is a plastic like circle with 6 holes of different sizes that rotates through a measured point. This is how the CAS knows which cylinder to fire.

Now you said the bracket had snapped clean off, meaning there is nothing really holding the CAS in place other than the fact the bolts are holding it through the timing cover. There would be a lot more vibration coming through the spindle and possibilty of it starting to rotate off of its axis.

Add to the fact that you said the semi circle in the exhaust camshaft has now snapped leads to the fact it has been vibrating and putting stress onto the spindle.

So without seeing the car and only going off what you have said, I can assume that there is a high chance of the CAS being damaged in some way given how sensitive it is. Even a slight movement of it can throw the timing way out.

So without being dodgy the way to fix this properly is to get a new exhaust camshaft, a new CAS bracket and putting it all back together to see if it works. If it is still running rough than most likely the CAS is damaged and you will need a replacement of that aswell.

[luvpsi]

well he said he has a new CAS bracket so all he needs now is new CAS and exhaust cam

[jiffo]

well he said he has a new CAS bracket so all he needs now is new CAS and exhaust cam

Just because the half moon locator has snapped doesn't mean he needs a new cam.

The CAS drives from the spline and if you can't initially get it as close as 1-spline out you need to give the game away.

Once you've got it running and have worked out which way the CAS has to move on the spline to keep the CAS within the adjustment slots, pull the CAS, rotate it and put it back.

Some aftermarket ECU's need far more advance than the stock CAS position allows, so the locator has to be removed to get the CAS around sufficiently.

Try a bit harder.

[JonnoHR31]

first thing to do is check the cas shaft. pull it off and look at it from the shaft side, spin it by hand and see if the shaft is bent at all , if it is then thats why the bracket snapped. if this is the case, find a replacement cas.

once you have the cas sorted get a small mirror and have a look into the centre of the cam to see where the half moon section (even if its broken off you can see where it was) is then align the cas so its half moon section is exactly oppostite the cams, then slide it in.

with a standard ecu the cas bolts should be roughly in the centre of the slots, which will get it running. but you need to set the timing with a light before driving.