[wixthedog]

Taking a sample is a good start, you'll have to drain the whole tank or make sure you draw from the lowest point of the tank since water settles. I do not put much stock in pour in chemicals so your mileage may vary there.

It may even be an ignition issue, a weak ignition coil may be erratic and not allow enough spark or not be able load back up in time. You can test it with a decent multimeter or you may even be able to take it to your local parts store for testing.

Good luck!