[John65]

I have just aquired a 1999 Astra 1.6 8v automatic, and have intermitent starting problems.30% of the time it refuses to start although it turnes over ok, it usualy starts within 5 mins. This happens in the mornings and sometimes early evenings.Nothing shows up on diagnostic check. It is noticable that the cooling fan comes on most of the time this accures and runs on for a few minutes although i have turned the car over from cold. also the rev counter occasionaly rises from 2000 to 3000 for a verry short time, although my speed is constant at 2000 rev. Help Please

[Hometune]

Was the actual value displayed on live data of the coolant temperature sensor during the diagnostic check? Was the cranking engine speed checked on live data? Both could prevent the car starting.
The cooling fan coming on with a cold engine is likely to be the radiator fan switch mounted in the lower half of the radiator.
The rev counter suddenly rising could be: faulty crank sensor, faulty speed sensor or dash problem. Was the car driven with the scanner attached in live data to see what signal the speed sensor was giving?
If the 'diagnostic' consisted of someone connecting a cheap scanner and saying, 'no faults found' then you need to find a garage that knows what it is doing.