Shudder at idle

[00mike00]

I have the fuel injection GTX. 1.8.
At idle the engine appears to shudder quite badly. As soon as the car is given a little throttle it smooths out. What can be the reasons for this?

Edit: to add, this is in neutral only when the car is sat still. It vibrates.

Thanks

[unknownmale]

What is the RPM at idle? Just when cold or once warmed up too?

[00mike00]

Sits steady at 900. Vibration appears to be at any temperature.

[mark1gls]

Increase the idle to at least 950rpm but I find mine runs better at 1000rpm especially in the winter months with extra electrical things on.

Idle screw at the back of the throttle body, 7mm spanner needed.

Brass screw at the top of this picture (throttle body is obviously not on the car)

[unknownmale]

Might also be worth checking timing/ vacuum leak

[00mike00]

Thanks for the comments guys, I will check this out when I get home.

[mark1gls]

What petrol are you running on, super or normal unleaded?

[00mike00]

What petrol are you running on, super or normal unleaded?

I picked the car up on Wednesday but only yesterday did I go get some more fuel. I dropped in super unleaded, I certainly thought it ran better but still it vibrates on idle. Perhaps not so bad but I can't tell.

[mark1gls]

Super unleaded is the best fuel to run on.
Check for front and rear engine mounts, I've gone through a few front mounts in my time, the rubber usually starts to split so you should be able see a failing mount.