993 Faq Frequently Asked Questions about the Porsche 1994-1997 993


Humming noise from dash when I turn on the ignition

Filed under: Diagnosis — Jeff 993TT @ 5:41 pm

Our p-cars make several strange noises when inside the cabin, even when the car is not running.

Before the car is started, a humming noise from the trunk area usually means the brake pressure accumulator is running. ( ONLY applies to C4s/TT cars )

After you switch off the ignition, you may notice some humming from the climate control unit. This is the CCU monitoring the air temperature. This is normal too. Although I don’t understand why it would continue to do so after the car is switched off.

Tapping noise on startup

Filed under: Diagnosis,Engine — Jeff 993TT @ 5:38 pm

One engine modificication from the 964 was the addition of hydraulic valve lifters to the 993 engine. Advantages are they 993 owners don’t need to adjust the valves every 15K miles.

Unforutnaltey, there is increased engine noise on startup in the form of a ticking noise. If this does not go away short after running the engine or you noice a power decrease, then you should consult your mechanic.


Filed under: Diagnosis — Jeff 993TT @ 5:21 pm

OBD stands for On Board Diagnostics. This is a standard in the automotive community which monitors exhaust related items and records them.

Things that OBD monitors are:

a) Oxygen sensors
b) Misfire
c) Knocking

And others. In addition to the standard part of the codes, Porsche has a entire set of custom codes. You can read these out with a an OBD tool, but you will need to buy the Porsche books to decode what they mean.

You can buy the tool to read the OBD codes from www.obd-2.com and you can buy the books from www.my-porsche.com

How to diagnosis the check engine light

Filed under: Diagnosis — Jeff 993TT @ 9:42 am

This is usually an emissions related issue.

The first thing to do is to find out what the fault code is. You can buy the tool to read the OBD codes from www.obd-2.com and you can buy the books from www.my-porsche.com to decipher the meaning.

There are some common codes ( misfire, etc ) which do no require the books, so getting the tool alone is worthwhile. There are also Palm OS based ones as well.

This tool will also reset the CE light too.

Common sources of the CE light are:
a) Gas cap not on tightly
b) Knocking
c) Misfire
d) Oxygen sensor bad or faulty

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