How about how many amps does a vehicle pull at idle

Still depends on many things : state of battery charge, other items such as heater blower, not an easy answer...

Just enough to run the minimum may be 5 amps if the battery is fully charged but more if it needs charging.

Typical Current Loads for Automotive Systems, Lighting, and Accessories:

• Engine Idling (no lights or accessories on) - 35 to 50 amps. This will vary depending on the number of cylinders (more cylinders draw more power for the fuel injectors and coils), the type of fuel injectors (some draw higher amp loads than others), the type of ignition system (single-coil or multi-coil), the amp draw of the PCM, and the fuel pump (the amp draw will be higher with higher pressure systems).

Explanation:

• Engine Off (nothing on) - 40 to 50 milliamps (power drain by modules in sleep mode, antitheft system, and keyless entry)
• Ignition Coil (single oil-filled coil older vehicle) - 3 to 4 amps.
• Ignition Coil (single DIS coil newer vehicle) - 5 to 6 amps at peak output.
• Ignition Coil (coil-on-plug) - 6 amps per coil at peak output.
• Ignition System (primary circuit) - 6 to 20 amps.
• Fuel Injectors - 4 to 6 amps peak, 1 amp hold
• Electric Fuel Pump (depends on pressure and flow) - 4 to 12 amps
• Electric Cooling Fan (depends on the size and how it turns on) - 6 to 30 amps
• Small bulbs (LED, usually in a new car for dashboard) - 0.04 to 0.06 amps per bulb
• 500 Watt Sound System (OFF)- 20-200mA (depending on the deep sleep state)
• Electric Power Steering - 2 to 40 amps depending on load

Assuming it is Gasoline With 50mA idle for security module + Ignition Coil 5A peak + Ignition system 10A peak, with a Fuel injector 5A peak, Electric fuel pump Avg 8A peak, Electric cooling fan OFF, the small bulb on the dashboard ON 0.05A, Sound system off drawing 100mA, without any electric power steering, and without AC ON, and any heater OFF will be peaked about 28.2A on idle.

But because it is a peak amperage draw, it will not always draw 28.2A, if you test it with multitester or DC Clamp current meter it will just reading as low as 8-15A because it is averaging your current, because your current is not straight, more likely to be pulsed current draw.

Source: AA1Car.com