Revs moving when idle??

[1.6mk4GOLF16v]

This morning just as i got to work i noticed that after i had parked the rev counter wasnt still as it should be
Every second or so it would drop 1000rpm so it drove it round the block, parked up n its still doing it 
Opened the bonnet and the engine seems to give a bit of a shake aswell, dont sound to healthy neither!



What could it be?

[Adam]

Mine does that when I have the Air con on.

That engine is giving you a lot of trouble. Time to change?

http://www.golfgtiforum.co.uk/index.php?topic=58241.0

[rubjonny]

was it really 1000rpm, or 100rpm?

[1.6mk4GOLF16v]

  u know what i mean, still does it on the odd occasion, could the coil packs be faulty?

also im suspecting that the cars sometimes running on 3 cylinders as it gets really sluggish after driving for approx 30 mins

gonna plug in VAGCOM tomorrow morning to check for fault codes, aahh another question can VAG be used while the engine is running?

gotta change the spark plugs tomorrow aswell

[rubjonny]

good idea and yes it can

[1.6mk4GOLF16v]

so whats the difference of using VAG while engines on or off?

[rubjonny]

well you can read fault codes etc with the ignition on regardless of if engine running, only difference is with engine running is you'll see parameters like engine rpm etc actually read something

[1.6mk4GOLF16v]

aahh ok, ill give it a go and let you know the outcome