If I read your original post correctly you state that the problem happened as you were pulling away from the service station. There is a considerable volume of fuel in your car's plumbing that would need to be burned through before the bad gas/water would reach the injectors. If it was several minutes after driving away from the station that the shudder started then I might consider bad gas, but immediately when pulling away from the pump? I just can't see the gas causing that.

Robert

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