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MG ZR ZS ZT Technical - V V C Working?

Is there any way you can test if the vvc is advancing?

Thanks
d cusworth

A rolling road dyno graph would give you a very clear idea as to whether the VVC is working as it should.

What's the problem you've got with yours?
Rob Bell

slightly uneven idle,especialy when aircon is on, stalls very easily, lack of torque & power from idle to 3000 revs, a bit dissapointing realy - this is on a ZR160 which i have driven from 4500 miles to 12000 miles - the car has not changed - it has always been like this! (car was ex MG and had stood for 10 months someware befor i got it at auction)
danny

Danny, this doesn't sound specifically like a VVC problem. In fact, I am wondering about a number of different problems - but I presume that you've been back to the supplying dealer and had the car connected up to Testbook to check on the operation of all the sensors?

If all the sensors check out (crank and cam position sensors specifically), then I wonder whether the cam timing is correct?
Rob Bell

it was an auction win!
danny cusworth

Hi Danny,

Agree with Rob that it doesn't sound like a problem with the VVC mechanism, at a guess it sounds more like a weak spark problem. If the car stood for a long time without being run then the HT leads may have suffered - might be worth trying a new set.
Mike Hankin

when the vvc advances, do you feel anything? at what reves does this happen?
the car doesn't missfire per say.
danny

The effect of the VVC won't be felt until 5000rpm revs upwards, there's a slight surge but only slight. If your VVC wasn't working you'd feel the power dropping off around 6000rpm, as opposed to pulling strongly to the red line.

Another possibility is that the injectors are fouled - have you tried some injector cleaner? The STP stuff works quite well.
Mike Hankin

Danny, the VVC is rather more sophisticated than the Honda VTEC, so no crude kicks in the back when the second cam profile comes on stream: the VVC is continuously adapting and gives a near linear power curve.

You've got bad running from idle - and really the only way to diagnose this is to go back to first principles: is there adequate fuel, is there adequate spark, and is everything being timed correctly?
Rob Bell

4000 rpm on feels quite strong - its the 900 - 3000 bit that feels flat maybe the cam is stuck in the "advanced" position
danny

VVC's tend not to do that - rather the timing advance tends not to work. I'd look for other causes of the problem...
Rob Bell

ok -thanks!
danny cusworth

This thread was discussed between 02/05/2006 and 05/05/2006

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