Failing crank sensor will cause these symptoms. Diagnostics might confirm, but can be expensive.
If you chose to just replace the sensor (which, TBH, is what I'd do) it's fairly simple, just make sure you route the cable correctly so it does not contact anything hot. If you have air-con it can be a bit of a fiddle.
Don't buy cheap ebay copy parts, better to spend a bit extra and get a decent one from somewhere like Autovaux, or if you have the money, a proper Vauxhall one.
fred, December 2011
