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Porsche’s 928 is surprisingly contemporary considering it was designed a quarter of a century ago. It was meant to be a successor to the venerable 911, but the 911 would not lie down and die so it became a stablemate, and in it’s final incarnation, the GTS it was some stablemate - a 350BHP, 175mile an hour supercar.

The 928 was dropped in 1995, and one of the reasons for dwindling sales was its reputation for maintenance costs. There is no doubt that it is a complicated beast, with many systems being microchip controlled, which was cutting edge technology in 1979. Porsche also pushed the boat out with mechanical complexity, and any components which are dedicated 928 and only available through Porsche are horrendously expensive.
Inlet manifold
Engine mountsDoor catches

DIY maintenance is an option, and I will document any jobs I do, along with references to other sites so that others can benefit. These pages are my own personal experiences and are meant as a guide, you are responsible for your own repairs!

All work shown here is on a 1991 S4 Auto.

When I bought the car the engine mounts were shot, so that was an intended job, but before I could get round to that I had an idle problem - the car would idle fine for a while and then just die, which became a real pain in traffic. It would start straight away.

The MAF was out of calibration, so that was changed, and I thought I must have a hose leak under the inlet plenum, so that came off and all the hoses were replaced, the butterfly mechanism was thoughroly cleaned, the slow run valve was ultrasonically cleaned and checkd, and the injectors were serviced, cleaned and checked on an ASNU rig.

The problem was finally chased down to a poor connection on the temp sensor - it has two channels, one to the EZK fuel computer and one to the LH ignition computer, and if these signals differ the system gets confused. Just removing and replacing the self cleaning plug fixed the problem,

Some very useful links:

MAFs and ECU problems. The MAF will most probably be out of calibration at about 100,000 miles, and the LH ECU is another weak area.

If you have any problems with these items then John Speake is your man. Email  info@jdsporsche.com or check out his website: www.jdsporsche.com