VVTi Problems

[monsi]

Hi all,

I'm having a strange noise coming from the top right of the engine (timing chain end), I thought it was the tensioner and removed the valve cover to check the timing chain. There was quite a lot of slack so I've replaced the tensioner and thats now gone but the noise has still remained.  The noise is most noticeable around the 2000-2500 rpm sounding a bit like a diesel rattle.

I am running a standalone ECU so don't have any EML errors, however I can see that the VVT cam isn't following the programmed curve. It would normally sit fully retarded at 0 degrees when at idle then the angle would increase as the rpm increases and the cam advances, now instead of increasing the angle decreases as the revs increase up to about -5 degrees and stays there.  I have also tried changing the duty cycle going to the VVT oil control valve - this used to advance the cam position causing the engine to stall at idle - this no longer happens the cam refuses to move.

I think that either the VVT oil control valve, it's filter or the VVT gear are the most likely causes of these problems, has anyone else had any similar issues? or better still a solution?

[jonbill]

Do you have a reference for the change curve you expect the cam to follow? It's the opposite of what I'd expect.
If the noise isn't the timing chain, maybe it's a bearing on the water pump or alternator etc on the ancillary belt.

[SteveJ]

Possibly a failed vvt control valve - I've heard one that sounded like a bag of spanners when it starts to fire at around 2500 rpm. Turned out the valve assembly had parted company internally from the solenoid plunger.

[monsi]

I've not got the exact map with me at the moment but I expect the cam to start fully retarded (which is 0 deg on my system), as load/rpm increases the cam moves more advanced (a positive number) then towards the max rpm the cam move back to fully retarded again.

I suppose a quick run with the accessory belt off would rule out water pump or alternator, how quick does this need to be?

A failed control valve sounds the most likely, I just hadn't found anyone who had similar sounds to mine, any idea if it can be removed with the alternator in place?

Thanks

[Carolyn]

It can be removed with the alternator in place, but it's really fiddly. Then you can bench test it.  Once it's out you can get at the filter (even more fiddly) and make sure its clear.

Edit:  If you remove the belt, the top bolt from the alternator and then loosen the bottom bolt, you can swing the alternator out of the way.  Still fiddly, but much better.

[monsi]

Thanks Carolyn, sounds like I'll be moving the alternator out the way!

Still I'm off on holiday Friday so it'll have to wait until I get back, but I'll keep everyone updated

[Ardent]

Monsi

Use the search function to confirm. But from memory if you put 12v across the terminals of the ocv it should fully activate and the engine should stall. (if its working)
confirm before you do though.

Edit
or, if you happen to be passing anywhere near loughborough, drop in on steve at D1 Customs.
He could hook up his tester and run a positive test on it. Basically override the ecu and command it to fully activate. The quicker the car stalls and dies the better. Oddly.

[monsi]

Hi Ardent,

Yes, that is correct, and mine doesn't stall.   s:( s:(  

The 12v causes the valve to open fully advancing the cam causing most of the air/fuel to blow straight out of the exhaust and the engine to stall.

Thanks