Idle Issues

Hi Rich,
I think I could use your help in diagnosing my idle problem. 
I have an 1987 928 with about 38K. 
The car was having a tough time starting so I replaced the spark plugs, ignition wires, 1 ignition coil, ignition rotors, ignition rotor caps and the temperature sensor on the front of the engine.
I the cool months in Tampa, Florida it started up without problem.  After I drove it for a while it was hard to start but I could pump the accelerator and it started.
Now that summer time is here it has a hard time starting and wants to cut out when I'm idleing at a stop sign.
So it might be the MAF but I don't know.
Your help would be appreciated.  I've never removed an MAF so any instructions would be helpful.
Gil

Hello Gil,

There are many possible causes of an idle problem. 

One common problem with 928s as they age are the diaphragms in the fuel pressure regulator and fuel presser damper.  The fuel injected pre-1987 928s had two fuel pressure regulators and one damper, where the 1987 and newer have one fuel pressure regulator and two dampers.  If the rubber diaphragm in these items leak, unmetered fuel leaks into the intake manifold and the engine will often stumble and flood out.  I've had this problem with my 1987 and 1993 928s.  One test is to remove the vacuum line and look for fuel leaking out or smell for a fuel oder.  Another test is to use a tool like the MightyVac and pull a little vacuum and see if the vacuum holds ... if it doesn't then the diaphragm is likely leaking.  They're expensive (what isn't these days), but after 30 plus years I'd call them an item that should be replaced just due to age.

Check these items and let me know what you find.

Best regards,
Rich