It seems that every Zed owner and his dog has had rough running at some point, but I thought I'd ask the question in case these are characteristic symptoms....

 

Up to a minute or so after fire-up, the engine seems fine.

 

Once it's warmed up a little I get the following problem:

 

With the engine below 3000rpm and at low load, the engine note doesn't seem quite right and under light acceleration the car will judder/jolt. However, somewhere between 2500 and 3000rpm it will suddenly sort itself out and run smoothly. Similarly if you put your foot down below 3000, it will pull smoothly up through the revs.

 

When thoroughly warm, the problem's less apparent, but still there.

 

Originally I thought this was related to vacuum pipes as there were several which had loose connection with the plenum/balance bar, but having now replaced all the troublesome ones I've still got the problem. :(

 

My current thoughts are that this is a air/fuel regulation problem, but there's so much to check I thought I'd pick people's brains.

 

Any thoughts on where to start?

i had a similar problem on my zed but below 1500rpm

turned out it was something to do with my aiv valves weired i know,

how i found out was on the rear of the balance pipe on the drivers side theres a vacum take off for the aiv valves, i pulled the 6mm vacum hose off the end of the balance pipe & put my finget over the hole in the balance pipe, the fault dissapeared straight away food for thought just incase its not your ptu :nelson: