Porsche Repair: Porsche 86 Loss of Power/Rough hot idle, camshaft lobes, porsche carrera 911

Question
Dave,
Intermittant loss of power in steady cruise. Sometimes it recovers under accerlation sometimes not. Usaully restarts after a few attempts. Cold idle seems ok. However, during hot idle, idle speed is very erratic & fluctuating with Black exhaust smoke cycles! It performs the same with or without the O2 sensor connected. Any ideas?
Many Thanks, Rod

1986 Porsche Carrera 911, 3.2L, (Non Turbo)
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Answer
Hi Rod,

Good descriptions, but with so much going on, there are quite a few possibilities as to the culprit(s).  At this early stage, I can only list the probable areas of concern...each would have to be checked and then tested to see if improvement is noted.  I suspect there may be muliple concerns at play.  Here's the top 8:

1.  Vacuum leakage
2.   Air filter clogged
3.  Fuel pump not delivering sufficient fuel to the injectors (volume), or injectors clogged
4.  Head gasket failure
5.  Camshaft lobes worn
6.  Fuel filter clogged
7.  Faulty or incorrectly gapped spark plugs.
8.  Distributor cap issues...cracked cap, disconnected or faulty wires, or worn components.

Unfortunately, I'm unable to suggest any tests that eliminate large numbers of these concerns...they have to be worked through patiently and thoroughly.

Dave