Was driving earlier to see my mum as she has just come out from hospital, stopped at a junction and the old Seris 1 Rs started idleing from 1000rpm to 2000rpm flickering between the two....the engine was running really fast so turned back home.

I have a rattling tappet, would this cause a problem??
Car is booked for a cam kit change monday.

Any ideas?? need to solve before xmas as i iwill be skint till feb

 

Sounds like an air leak to me.

 

I changed the rocker cover and charge pipe...been a hissing noise since then.
Could it be that?