[Bill Wagner]

Hi John:

I've only owned my 964 for over a year, and I'm NOT an expert on it's electronics yet, so a good deal of this is speculative based on my experiences with other cars.

I'm assuming that "closed loop lean not reached" means that the O2 sensor can't drop down to what it sees as a lean condition, or the ECU is misinterpretting the data it's getting from the O2 sensor. As I'm sure you're aware, the O2 sensor puts out signal levels based on oxygen content in the exhaust. Typically these are programmed in the ECU in an almost binary fashion...at a low extreme the ECU says "I need more gas", at the high extreme it says "I need less gas", and then it's supposed to adjust accordingly. The same applies pretty much for air in the systems since air and fuel make up correct fuel to air ratio.

Obviously you're faced with an imbalance. The only things that I can think of are the following:

1. An injector is stuck open (or sticking) and either putting too much fuel into the system all the time, or putting too much fuel into the system when open, hence the "lean" level the O2 sensor wants to see is never present. My guess would be an injector is stuck open, otherwise the problem would be erratic. To test this you could probably do an emissions test and see if the output is too rich. If it is, I would disconnect the electrical leads to each injector one at a time, and ONLY one at a time. Of course you will be creating more problems, but the car MAY react differently on one or two injectors, indicating the problem boys.

2. Make sure the air intake mechanisms are operating properly....all the "flaps" are opening properly, etc.

3. Use another O2 sensor. Things are never perfect, and you COULD have a bad one, but it's unlikely.

4. Look for problems with the cables and harnesses themselves. This will likely be the WORST problem to troubleshoot since it would amount to sequentially replacing all cables/connectors with new units until the problem is isolated.

Hope this helps,

Bill Wagner