Hello

My 9000CSE has just started having this fault, when I have the engine at
idle it sits at about 1200RPM then goes up to 2000RPM then after a couple of
seconds drops back to about 900RPM then repeats this going up and down after
a couple of seconds. I had it serviced a week ago as the check engine light
came on so I took it to the garage and they serviced it but now a week later
it has got this fault, I don't know what is making it happen and I don't
know if something maybe the garage did has caused this? I don't want to take
it back to them and tell them they hadn't serviced it correctly if they
haven't caused it.

Paul