■ Engine: Engine smoke when warm hints at worn valve guides and cylinder bores. Check the oil level and try to gauge oil consumption (500 miles per litre is typical). Lumpy running could be a worn distributor or failed ECU; vibration at idle may be worn engine mounts. Timing belts, tensioners and water pumps should be changed every 60k miles or four years. Check for coolant leaks; Porsche coolant needs changing every four years.
■ Transmission: Check that the torque tube connecting the gearbox to the diff isn’t putting pressure on the flywheel mounting plate. Examine the underside of the automatic gearbox and torque converter for leaks. Rare manual ’box has a notchy change but too much stiffness can wear out the synchros.
■ Brakes, steering and suspension: Check the brake lines and hoses, steering and driveshaft gaiters, and suspension arms and bushes. Clonking could mean worn bushes; a floaty ride suggests worn dampers.
■ Body: The galvanised 928 has aluminium doors, front wings and bonnet but check for bubbling around windows and the rear hatch, and the underside for corrosion. Tired sunroof and tailgate seals can cause damp carpets.
■ Interior: Check all the electrical systems work. Where fitted, a failed air-con suggests penny-pinching elsewhere. Expect trim and upholstery to be worn or torn, so factor refurbishment into the price.
Also worth knowing
In the Porsche Classic section of the Services & Accessories menu at porsche.com/uk you’ll find a wealth of information on the 928. There are links, too, to Porsche’s classic parts catalogue that includes the 928 plus the opportunity to tell the company’s product development people about that rare part you require.
How much to spend
£3000-£15,999: From tatty left-hookers, via a rhd ’82 S auto with 90k miles to a Cat C lhd ’91 S4 auto with 128k for £15,995.
£16,000-£19,999: Includes a ’91/H S4 with 112,000 miles for £19,900.
£20,000-£24,999: Includes an ’82/X 928 manual with 80,000 miles for £21,500 and an ’88/F S4 with 75,000 miles for £24,995.
£25,000-£29,999: More S4s, including a ’91/H with 85,000 miles for £27,950.
£30,000-£39,999: Includes a 1991 GT manual with 108,000 miles for £37,995.
£40,000 and above: More GTs and low-mileage S4s in mint condition.