A2 GTI 8V Digifant II Possible Bad ECU?

No chance that it's the ECU section that deals with the O2 Sensor?

I didn't even know there was a problem until about 2 days ago. The wires to the O2 Sensor were severly jury-rigged. Some of the wires were bare, possibly touching each other. At the OEM O2 Sensor connector (removed now) there was some evidence of a meltdown or possible fire. All of this mess was wrapped in a nice red electrical-taped bundle. Well, the bundle got wet 2 days ago and I started having big problems with getting the car to stay running for more than about 30 seconds.

Plus, my MPG weren't terrible, but they aren't great either- about 21 around town and 25 highway.

Yes, but perhaps the ECU section that deals with the Digifant was fried with the mess of wires? Either previously or recently when the wires got wet?

How long would it take for the sensor to be fouled or contaminated? I've had the current O2 Sensor in the system for about 4-5k miles or about 2-3 months.

Interesting. I also noticed what seemed to be too much carbon on the plugs when i pulled them to check them. So would you suggest replacing the O2 Sensor first and then the ECU if the Sensor doesn't fix the problem? I know that the Sensor is a whole lot cheaper...

Will check. Thanks.

Nope, but I will now!

Where in Perth are you from? My wife is from Perth WA. And her parents still live in Ocean Reef, a suburb (or the Aussie equivalent) just north of Perth.

Ciao, Craig

Don't forget to consider the other common Evil Digifant Sensor, the blue CTS. Just because all logic would suggest your O2 sensor is the problem doesn't rule out the blue CTS causing trouble (which can sometimes be masked by an also-bad or intermittantly-bad O2 sensor, at least in my experience), and which will definitely cause plug fouling.

Of course, don't forget to clean the plugs, too..if you you're running fouled plugs, you're not going to get particularly good performance even if everything else is to spec.

I had the same problem. I used the generic 13913 (or something like that) bosh O2 sensor. Works fine until the engine heats up. Then loss of power and black smoke. Finally broke down and purchased the OEM replacement from local O'Rielly parts store ($109.00). 100 miles so far so good. The exhaust even smells cleaner.

I have a 89 Jetta 1.8 8v RV DIGI-II German build. New cap, rotor, wires and now O2 sensor. Runs great.

Very tiny probablility.

Unlikely, unless it shorted to HT.

The O2 sensor circuit is basically a high-impedance input trigger circuit that detects the sensor's switching about the nominal 0.7V or so and feed the pulses into the microprocessor. [That's an educated guess; I didn't reverse-engineer.] If it got a continuous

12V, it wouldn't have done any damage. If it go 30kV or greater from the ignition, well; you're out of luck; but the whole computer would probably have been taken out!

Fouled? Minutes! Contaminated; depends on the fuel.

[snip]

Try the sensor first; *after* checking the wiring back to the ECU connector for shorts and continuity.

Small world is all i can say; except that Ocen Reef is 2 hours' drive North from here.

Yup, that fixed the problem. I can now say with authority that (at least on my A2 GTI 8V) the Bosch 13913 O2 Sensor does not work. And that the correct

13936 did the trick.

Thanks for all the help guys!

Craig Smith