dave944

I used 2000 or 2500 grit wet/dry, kept the hose misting continually, and just sanded away the top white layer of paint, one panel at a time. I watched for the little raised dimples to dissapear. Make sure you have good light. Having a red car makes seeing the oxidation easier. If you have a white or silver car I would be very careful to not sand off too much. I have also heard to soak the sandpaper in water with dishsoap or blue corral for 30 minutes or overnight before starting, to soften it up and reduce scratching. Anyway, I tried some cheap polish (nu-finish) I had laying around last night, and it polished right up and looks great, both the enamel and the acrylic areas. It remains to be seen how long the shine will last. Prior to wetsanding, the oxidized paint would hold a shine for a very short while before dulling, even after using rubbing compound, due to deep oxidation. I guess this is due to the porosity of the oxidized layer. With the oxidized layer removed I am hoping it will hold a shine much longer. But again this is drastic action for a 22 year old 944...

This may be flagged off topic since it is a 944... The car is a chalky red color with enamel paint. A detail shop recommended I start with a good wet sanding to remove the oxidation, and then have it buffed. I had the guts to try this and was surprised to find red paint under the chalky red that looks buffable. However some of the panels are repained, and not enamel, but acrylic instead. Instead of revealing a deep red color, some panels got more chalky due to the fine scratrches the wetsanding made. Outside of the obvious color match problem how can I recover these scratched panels?

this is mysterious. if you followed the heater circuit procedure for the front and got nowhere, and there is no procedure for the rear codes, I would go back to square one and run the overall DME diagnostic performance checks in the book, if there are any.

check the heating circuit with a volt meter. There should be 12v on the heater lead at the O sensor. what does the book say about checking the front O2 heater circuit? It is probably the same for the rear.

Sorry the diagrams and flow charts didn't save on that last post. But the idea is that each auto manufacturer should have a factory service manual for the electronics that will take you step by step through troubleshooting these problems and codes. It is usually a flow chart diagram. This is where you can educate me on how to find these manuals for a porsche boxster. I would expect a dedicated manual just for the DME since it so complicated. I have seen a Bosch manual dedicated to emission control systems but don't know what cars and years it covers. Also if the car is OBD-II compliant, that means you can plug the standard automotive computer diagnostic equipment (found at any shop or auto parts store) in and see what the computer thinks is happening when the engine is running. Most cars sold in the US starting in 1997 are OBD-II compliant. This is a law to help the emissionc ontrol inspectors as well as repair facilties. A quick check shows Porsche became compliant with OBD-II in 1997. There are different levels f sophistication in this equipment. There are handheld code scanner that just reads and clears codes, that sells for less than $100. There is software that runs on a laptop and uses an adapter between the OBD-II port and USB port for around $200. It will read and display all that is going on in the computer and display really cool graphs and charts of all of the sensor reading including temp, O2, RPM's, throttle position, spark advance, etc. but you still need to know what you are doing to make heads or tails of these readings. There are also more sophisticated handheld units that will do many of these things.

I recommend you use the factory trouble shooting flow chart for this car and these troube codes. Here is an example for a Saturn. 1997_Saturn_SL2_1_9L_DOHC.htm

Reseat the harness connectors at the computer. Also some of the sensors in the engine bay.

I went thru something similar on my 97 Saturn. Replaced front O2 sensor and the code kept coming back. Asked Saturn and they said use OEM sensor, and not Bosch. Tried Denso OEM sensor and same problem. Was going down the path towards thinking I needed a new computer. I called an automotive techline for advice and they suggested a loose wiring problem. Well after disconnecting and reconnecting to check continuity of wires, including the harness connectors at the computer, everything magically cleared up. Conclusion it was a loose connector at the computer that had worked itself loose through vibration over the years. End of story! They also said the O2 sensors at the rear of the Cats don't do anything, either, and rarely need replacing for performance reasons. The front sensors are the ones involved in controlling the mixture. However if the rear O2S has a wiring fault it would probably set off alarms such as you MAY be geting. /Regards/

That makes sense for a v-6 that weighs around 3000lbs. Even with taller gears the mileage probably wouldn't improve much as the computer keeps the mixture optimized for the amount of air entering the combustion chamber. It would be nice if there was a warp drive that got 40mpg though! most likely the biggest variable affecting mpg is air temperature. laws of physics are in your favor with higher temperatures. the air is less dense requiring less fuel to meet designated mixture pre-programmed into computer. also lubes thin out more and cause less friction. and air expands in tires providing slightly taller gearing. but keep the A/C off for best results. Also much better to state the computed mpg (miles driven since filling up divided by number gallons to refill) than the miles between fillups when comparing fuel economy since some run it down to empty and others fill up at 1/8 or 1/4 tank.

I agree, but might also check the vent temperatures (on the highway) with a dial thermometer to see how cold things are really getting. As I recall upper 30's F for an R134 system.