Engine problem

[Sirrith]

Hi all

I'm having a bit of a strange issue with my Z. When I start the engine after a long period of no use e.g. overnight, and put it into drive (its an auto), the rev counter will bounce up and down between around 1k and 500 rpm, and the car will lurch forward a few times matching the revs, without me touching the accelerator. First time this happened it caught me by surprise and almost sent me into the garage wall as the car accelerated for no reason...

Any ideas what could be wrong?

It goes away after about 10 seconds, and I can't reproduce it on the same day.

[Busterboo]

Go to your local auto box specialist to eliminate it as the problem. (If you're near Leicester, I know a very good one.) They'll usually tell you what's wrong for nothing.

[Sirrith]

Thanks, but unfortunately I'm not in the UK, I'm in Hong Kong and we don't have any free services like that over here to my knowledge

[ph001]

What engine?

[Sirrith]

What engine?

Sorry, should have included that. Its the 2.5L N52 I6

[ph001]

I’m tempted to think its not a gearbox problem as if the revs rise the transmission will do that. I’d wager a small bet on the eccentric shaft sensor or the Valvetronic motor. Do a search on here for both those for some bedtime reading. First relatively easy thing to check is if there is oil on the sensor.

Also a chance it could be the vanos solenoids, which would be good as they are both very easy to change and inexpensive. Sometimes just a good clean of them does the trick.

Had a scanner on it yet to check for codes?

[ph001]

...final thought, when it’s exhibiting the strange behaviour, give the Valvetronic motor a tap with a wooden mallet. If it stops doing it, there is your problem.

[Sirrith]

Thanks! I will check that out. I did have a code scan before buying it, which was about 1 month ago, nothing out of the ordinary. No more updated scan though.