ive noticed a few times that my estima shudders while stood, its got worse now if im parked and i rev the engine it cuts out, today as i was driving and slowing down it cut out! not good it happened 5 times! but it only happened when it had warmed up, as i did school run this morning it was fine. my dad has changed the spark plugs as they were a little grubby but its still the same, he is trying to speed it up a bit as it does run a little slow i hope it works, anyone had a similar prob?