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Porsche
Repair Questions and Answers

Question:
1990 Porsche 928s4 5.0 mileage: 159,999. Hard start
- when started runs rough and no power or intermittent
power. Was working fine before and after having
Midas check my catalytic converters. Verdict on
cats was bad. Temperature on engine side of
catalytic, 300 degrees; temperature on muffler side, 210
degrees. Does this mean the engine could be having
troubles due to catalytic malfunction?
Answer:
To test for a plugged converter, drill a small hole in
the exhaust pipe right before the catalytic converter.
Install a temporary hose fitting and attach a long
rubber hose and a 0 to 10 pound pressure gauge.
With the gauge inside the car, drive up a hill or
accelerate and read the pressure. Normal is 2 to 3
pounds, restricted 4 pounds or higher. The
drawback to this method is the small hole will need to
be welded shut after the test; a minor job if you have a
welder.
Question:
1985 Porsche 944 mileage: 94,000. The Porsche
has been sitting around without being driven for a
couple of years. The oil was changed, battery
disconnected, and fuel drained before storing.
What sort of maintenance should be done before putting
the car back on the road?
Answer: Assuming you have not started
it yet, remove the spark plugs and spray some oil on the
cylinder walls (WD-40) and with the plugs still out,
crank the engine over until you get oil pressure.
Replace the plugs and start engine. Obviously, you
need to re-connect the battery, which might need
recharging.
Question: 1983 Porsche 911
mileage: 211,000. My car usually runs wonderfully,
however the last couple of days it has begun idling
rough. It still performs okay on the freeway, but the
exhaust smells a bit gas rich (much more than usual). I
wasn't sure if it was time for a tune up, or something
more. Help?
Answer:
If a major tune-up has not been
done recently, this could be the cause of your problem.
Replace the spark plugs, plug wires, fuel and air
filters, etc. Also, replace the oxygen sensor. In
addition, service the fuel injection system. Clean the
carbon deposits from the throttle bore and idle
passages. A compression check should be done also.
Question: 1980 Porsche 924
mileage: 90,000. I am helping a friend with a 1980
Porsche 924. When cranked (cold) the oil pressure (on
the stock VDO gauge goes to 2.5 bars). After the engine
warms up (about 5 minutes) the pressure drops to almost
0. The oil pressure light also comes on. I thought about
trying to use a mechanical gauge, but with the location
of the sending unit it impossible to get to. I wonder
how accurate the gauge is, do they go bad or become
inaccurate, or should I try to put new rod and main
bearings to see if this would help. Do have a
suggestion.
Answer: It sounds like the oil pressure
gauge is accurate. Your problem maybe one of the
following: a stuck oil pressure relief valve, oil
pick-up screen partially plugged or the rod and main
bearings are worn and allowing to much oil to escape the
system.

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