Hopefully i can help..
If possible can you describe when this seems to occur more? ie:- at cold or hot etc?
Any warning displays when this problem crops up?
What checks or tests did the dealer carry out etc?
Only when cold.
No warning displays.
The dealer did nothing except connect to their diagnostic system?
Doesn't drive smoothly.
Hi..there thanks for your responce..
Ok..if it doesnt run smoothly or idle properly then im not sure why the dealer didnt pick up on that..normally the first things to check really if its a missfire your experiancing as per not running smoothly would be your sparkplugs and what condition they are in - any discoloured or fouled plugs can usually give an idea on what cylinders are at fault be it faulty spark,coil itself or a problem injector - if they are cheap plugs then certainly have them replaced - another could be faulty o2 sensor on the exhaust again normally this can be picked up via diagnostics/live data if at fault - also check for intake leaks/manifold by spraying carb cleaner or similar in the correct areas around the inlet manifold.change in engine speed denotes an air leak, probably the inlet manifold gasket - you shouldnt have any intake leaks after the mass airflow meter..as this can upset the ecu trying to compensate for that extra air getting sucked in or unmetered air which passes through the MAF..