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I have a 2003 BA Falcon after filling with petrol it often won't start or idles extremely rough for a few minutes. Once it's idling again it goes like a charm, no miss or lag to be felt.

None of the dealerships can shed much light on the problem can you help.

From the "Ask Jack" archives - 18 September 2009

Sounds like a tricky one!

In a modern vehicle like yours the fuel tank is likely to be plastic, so rust inside the tank can be excluded. Moisture inside the tank is also very very rare in modern vehicles. However if the fuel source remains constant each time the vehicle faults, the supply may be compromised and a new supplier should be tried first.

If the fault occurs after the vehicle has sat for an amount of time (not necessarily only after gassing up ) then you may have a fuel pressure leak, this could be external through a seal or o-ring, or internal through leaky injectors or fuel pressure regulator.

I suspect though the fault could be related to the fuel tank's ventilation system. To keep the pressure within the fuel tank regulated, the tank incorporates a breather system. This may be plumbed into a charcoal canister which helps absorb the fumes. A blockage with this system could cause the pressure to build in the tank, when you remove the fuel cap the rapid venting of the tank causes a vacuum and can create an air pocket within the engine's fuel supply circuit.

It's faults like this where a core understanding of basic automotive principals is vital, a reliance on the electronic diagnostic equipment may not help a technician here.