Hi, Did one of these about 6 months ago, slight misfire at tickover/tendency to stall at idle/light on. After much headscratching turned out to be loose retaining bolt on exhaust cam pulley, it was chattering on the locating dowel pin and giving just enough variation in signal on cam sensor to cause a problem. After 2 weeks of looking customer told me it needed water every 2 days so I decided to do a headgasket on it. It was only while stripping down that I spotted it, good job I had my eyes open at the time.The play was only about 0.5mm but when it multiplied up at the diameter of the pulley it was about a tooth! I think in your case it's probably that crank sensor but it just goes to show the weird things that can cause problems.