Porsche Repair: Porsche Idles Rough, camshaft lobes, spark plug wires

Question
1988 Porsche 944 2.5L 4cyl. 5spd, AC,  Idles rough at start, stalls when I come to a stop after warming up.

Answer
Arthur,

Just to remind you, my expertise lies in the older 356 models.  Luckily, many early designs/concepts have lasted since the early 50's and appear in revised forms on 911's, 914's 944's, Boxsters, etc.  Where this happens I'll promise to try to give you the best answer I can.

There are two areas you've mentioned, idling and stalling.  There are many possible causes for these symptoms.  You didn't mentioned how long it's been since the car was tuned-up, which could have a large influence on these problems.  There are some overlaps in possible causes, but I'd treat them separately.  Here's what you should look for:

Idle lopes

1.  Vacuum leak
2.  Air filter clogged
3,  Fuel pump not delivering sufficient fuel
4.  Leaking head gasket
5.  Camshaft lobes worn

Idle misses

1.  Spark plugs worn
2.  Faulty spark plug wires
3.  Vacuum leaks
4.  Uneven or low compression

Stalls

1.  Idle speed incorrect
2.  Fuel filter clogged
3.  Distributor cap and rotor damaged
4.  Faulty or incorrectly gapped spark plugs
5.  Faulty spark plug wires
6.  Vacuum leak in fuel injection system, intake manifold, or vacuum hoses

I'd suggest examining each listed item above, one by one, choosing the easiest ones first.  When you choose an item, be thorough and careful.  For example, if you look at the spark plug wires, rather than trying to examine them in the car, take them out, put each wire under a good examination and consider replacing them if it's been any time at all since you know they were renewed.  That way, with new components, installed carefully, you'll either have the issue resolved or you'll be absolutely sure that spark plug wires CANNOT be the culprit.  Then you can move on.

Have patience and let me know as you go through the steps how its going...or feel free to ask a follow-up question if you wish.

Dave