VW Cabriolet running rich

If possible get the OBD1 scanner and retrieve the codes

I would Start with the O2 sensor and also check the EGR for carbon build-up.
I`m not sure, but how about if you temp sensor is broken. It could be in "warm-up" mode all the time which is rich.

Hello Peter !

Looks like its not obd1 code reader for VW but here is some info:

SELF DIAGNOSIS SYSTEM
The Digifant I ECU has built-in on-board diagnosis (OBD) circuitry. The circuitry monitors the normal range of system operating values, detects unusual values and other faults, and stores fault information for later recall. If the system detects a fault it illuminates a warning light on the instrument panel labeled "CHECK".
When operating properly, the light should illuminate every time the ignition is turned on and go out when the engine starts. If the light remains on after the engine starts it means that the system has detected a fault. If the fault is a temporary condition; the light may go out some time after the engine starts, but the fault will remain stored in the ECU memory.

CAUTION:Always turn the ignition off before disconnecting or connecting the Digifant I ECU connector or any test equipment. Doing so with the ignition on risks ruining the ECU

There are two ways to access the ECU fault memory. Volkswagen dealer service technicians use a special test instrument, the VAG 1551, to display coded fault information, test system components, and conduct a check of ECU output functions. The tester is connected to the ECU using a set of dedicated diagnostic connectors under the trim plate in the center console.
The fault memory can also be accessed using a special jumper cable, Volkswagen tool no. 357 971 51 4E with color coded white and black terminals. When the jumper is connected, the CHECK light will display any fault codes in a series of flashes. For example, two flashes, followed by three flashes, followed by four flashes, followed by two flashes indicates the code 2-3-4-2.

Courtesy of Mitchel.

Let me know about the codes your ECU shows and I look for them.

Good luck!

Peter !

Check this out:

RETRIEVING CODES
Turn the ignition ON. Connect the black end of the jumper cable to the black diagnostic connector in center console under shift boot. Connect the white end of the jumper to the white diagnostic connector.
After five seconds the OBD CHECK light should begin to flash. Remove the jumper, but do not turn off the ignition. Record the flashes.
When code 4444 or 0000 appears, then either turn off the ignition or reinstall the jumper to end code readout.
Possible wiring faults should be checked and corrected before replacing a suspected component. Once the fault is corrected, the permanent fault memory should be erased as described below.
CLEARING CODES
Make sure the ignition is OFF. Connect the jumper cable as described in RETRIEVING CODES. Turn the ignition ON.
After 5 seconds remove the jumper cable. The OBD light should flash 4444. Turn the ignition Off or reinstall the jumper cable to end the procedure.

Let Us Know on your findings!

Hey Peter !

Anytime!

We are glad to be at your service.

Thank you for choose 2Carpros.

Good Luck!