Porsche Repair: !981 Porche 928, sheet metal screws, air flow meter

Question
Hello,  My Porsche is only idleing at 100rpms and it should be at 750rpms.  I have replaced all the vacume lines and a new seal in the air flow meter.  I was asking,  what do you think the problem might be.  Do you think that it could be the air flow meter itself? Also I have a problem with the lights,  all the outside lights work except for the drivers side front parking light,  only one of the inside door lights work and only one of the inside dome lights work.  Sometimes the door light that works stops and then in a couple of hours it will come back on. Thank you

Answer
Hi Greg,

I'm sorry, I can't give you a hand with the idling problem.  

Your electrical problems could all be caused by the same thing...the problem that door light is experiencing...sometmes off and sometimes on.  A bad ground.

Each of these lights requires the light fixture to be grounded, that is, either the fixture itself is touching bare metal...usually the body; or, there is an actual ground wire linking the fixture to the body or chassis.  There is also the chance the fixture is supposed to be grounded by the fact that sheet metal screws touch the fixture while securing it to the body.  This setup is usuually the most problematic.  Many times in cars of your vintage corrosion will creep in where the bare metal once was...interrupting the function of the ground.  Sometimes it is sporadic because the corrosion hasn't yet completely ruined the ground connection.  

So, at each offending light, I'd remove the fixture or housing, clean up the ground or create a nice clean one, and try the light again.

Dave