My wifes car is ticking over at under 500rpm. It shudders when applying gas up to 2000rpm, then when I release the gas it will drop back down to 500rpm.
I turned on the AC and the radio and it dropped down to 250rpm then cut out. It started first time but its still 500rpm idle. Any ideas what it could be?
Lets deal with the Idle and gas because all cars tend to idle at a lower revs when the electrics are switched on. I think your problem might be throttle body related. You don't give an engine size but try a throttle body clean. Its easy to do on most cars and can have surprising results.