Mine is the same, its intermittent. I suspect a bad earth on mine. Ive replaced both batteries and it was fine for a while, then it returned again. Its very annoying. Im going over all the earth points this week to clean them up. Only other thing I noticed is that one of my idler pulleys is very very loud, possibly the alternator. Was thinking that it may be upsetting the alternator possibly. Get yourself a voltmeter and check your cranking battery, should be around 12.4 to 12.6V, Get someone to start the car for you while you check the V and confirm that your battery doesn't drop below 10V during cranking. If it does, its time for a new one. I ran my standard batteries for almost 8 years, probably wasn't a great idea but they never let me down. If your alternator is good, you should be maintaining around 14.2V on idle.
So, one thing Ive noticed when mine is playing up is that it will hold revs at 1000rpm until the car stops moving. I can come off the throttle and it will just hold on 1000rpm providing the car is rolling. This will go on even when i'm crawling to a stop, providing the car/engine has any forward motion, it will hold on 1000rpm and the second the car stops moving, it drops to 750. Really weird. This is why i'm guessing it may be the pulley due to it having a direct correlation with the motion of the engine. Ive been very busy recently and haven't had time to go at it. Ill report back with any more info once ive checked all these.
