930 Running Rough
 

Put the turbo away for winter in my warm garage, was running great before it went into hibernation, got it out for a mot today and thought good excuse for a run.

Starts easy but not good, does not want to run above 0.4 bar 3000 revs looses all power and blows black smoke also the tick over is now some 1800 rpm, I know the on board bar gauge can not be relied upon but seems to get up to 0.4 bar too quickly, seemed to clear for a few seconds but now seems permanent!


Any ideas? at least went through the mot!

kev

Black smoke, high idle and other symptoms could indicate a rich condition. Is the fueling system stock? If yes, you need a set of CIS fuel pressure testing gauges to troubleshoot the fuel system. There is a device known as the WUR (warm up regulator) that is critical. Your 930 also has two high pressure fuel pumps, both of which must be working properly to deliver the correct volume and pressure of fuel to the CIS fuel distributor.

This is a good read on how CIS works and how to test it. CIS Primer for the Porsche 911

Many CIS cars run rough after being parked for the winter. I add extra fuel system cleaner and drive at least two full tanks in the spring before I make any changes. Use up the old fuel before you do anything else. One of my favorite fuel additives is automatic trans fluid. It lubricates and cleans the fuel system components.

Sounds like you have developed a boost leak between the turbo and the intake manifold. pull the intercooler and check the o-rings. I had the o-ring between my intercooler and throttle plate fail and my 930 had exactly the same symptoms that you describe.

Found it thanks to a phone call to Bob Watson, Relay for Fuel Pump No.2 Item G



Now running like a dream!



kev

Look on the 930 board for the fuel pump relay mod it saves the relays from overheating because of the resistance of the power supply through the single fuse. a very worthwhile mod.