First and foremost you want to make sure the engine on this Mercedes 280E is running right. Any hesitation, misfire, vibration at idle, drivability problems are sure to cause the vehicle to fail the smog check. You'll want to absolutely have a mechanic look into these faults before you spend money on the smog check.
As far as the visual inspection portion of the emissions test, you can take a peak under the hood yourself. Look for anything disconnected; vacuum lines, electrical wires, ignition components, and the like. Anything looks out of place, repair prior to the test.
Your Mercedes 280E will more than likely be driven on a dynamometer during the smog check. Make sure your tires are properly inflated, the engine is sufficiently warmed up (20-30 minutes of driving prior to the smog test).
Your vehicle's gas cap will also be inspected for operation and proper fit. Make sure it seals the gas tank properly. Check the gasket/seal to ensure it does not have any cracks. Also ensure the car is not running hot. The radiator should sufficiently cool the engine. NOx is created when engine combustion chamber temperature rise above 2500f. This will cause your MBZ to fail the smog test.
Proceed with getting the smog inspection. If the vehicle fails the smog technician will hand over a smog check VIR report which will indicate which emissions your MBZ 280E failed for. The VIR can than be used to guide you further in terms of which emission components to look into. Good luck. Contact us after the smog test if you have trouble.
