Part 15
Enough about brakes and weight reduction, back to ITB EFI conversion.
During close inspection after dyno tuning, I discovered that the electrical cable from the wide band O2 sensor interface unit (14Point7 Sparten2 Lambda Controller) had swung down and was resting against the left header and the cable insulation had melted through on one side (Ouch!). The ECU was still getting a valid air fuel ratio (AFR) signal so I wrapped the wound with electrical tape and added more cable ties to keep the cable away from the exhaust header. Then I proceeded with test driving and auto tuning as I described earlier, but I knew I would need to come back and address the burned cable issue with a more permanent repair.
It's almost Christmas, the 911 is parked and covered in the garage to wait out the winter so it's a perfect time to make improvements to the EFI wiring. I had three items in mind: Correct the O2 sensor interface unit cable and add a connector between the O2 sensor interface unit and the ECU connector block, add a connector between the throttle position sensor and the ECU connector block, and replace the EFI switched power connector (power is sourced from the relay that originally ran the blower motor).
First, I bought a Weather Pack moisture resistant connector set and crimping tool for 12-20awg wire, 1/2/3/4/5/6 pin connectors. When the connector set came I read the directions and then practiced making several mock up connectors to get down the technique for properly crimping the wire and moisture barrier to the pins and then assembling the pins into the connector bodies (male and female). Only when I was able to make proper, reliable connections with the practice pieces did I start working on the EFI wiring (it took me three tries to get the technique down, plus one more sample on a multi pin connector before I was ready).
I decided to start with the single pin connector for the EFI switched 12V.
Next, I cut the three wires from the throttle position sensor to the ECU connector block and installed a three pin connector.
Finally, I went to work on the O2 sensor interface cable. First I removed all the existing cable ties and removed the electrical tape "bandage" from the melted portion of the cable. Then I cut the cable on both sides of the melted portion of the cable.
Before I proceeded, I re-read the documentation for the 14Point7 Spartan2 Lambda Controller to review the function of each of the six wires in cable. When I originally installed the O2 sensor controller the wiring schematic from Al at x-faktory showed four wires connected (power, sensor ground, sensor heater ground, and linear sensor output signal) and two wires no connect (simulated narrow band output, and sensor temperature LED output). After this review, I decided to install a LED so I could monitor the O2 sensor temperature. One failure mode of an O2 sensor is the sensor heater failing and this LED output will let me know if that happens - the LED blinks slowly if the temperature is low, blinks quickly if the temperature is high, and stays on if the temperature in okay. So on the ECU side of the O2 sensor interface connector, I stripped back the cable sheath about 12 inches and I installed a six pin female connector and clipped the blue sensor temperature LED output wire. Next, I made up a ground wire and connected it the frame of the electrical panel at the left rear of the engine bay. Then I installed a two pin female connector for the clipped blue sensor temperature LED out wire and the LED ground wire I had just installed. I then re-wrapped the O2 sensor interface cable with electrical tape allowing for the two LED wires to branch off the main cable.
I installed a six pin male connector to the O2 sensor interface side of the interface cable. I soldered a blue LED to two wires and installed a two pin male connector (the positive LED output is attached to the longer LED lead and the ground is attached to the shorter LED lead). I used adhesive backed cable tie mounts and cable ties to re-install the O2 sensor interface unit and route the O2 sensor interface cable up into the engine bay through the hole in the rear engine mount that was originally used for the secondary air injection air pump plumbing. I slit a piece of vinyl tubing lengthwise and installed it as a grommet for the hole in the rear engine mount. I used adhesive backed cable tie mounts and cable ties to secure the O2 sensor interface cable and the sensor temperature LED to the rear engine mount.
I checked and rechecked all of my wiring connections. I checked to make sure the fuel line connections to the fuel rails were tight. I installed the velocity stack / air filter / rain hats. I lowered the car off the jack stands. I connected the ground cable to the battery. I connected my notebook PC to the ECU with the TunerStudio application running. I turned the ignition switch on - checked for fuel pressure and no fuel leaks. The blue sensor temperature LED was blinking slowly (low temp - engine isn't running). I opened the hand throttle a bit and checked for neutral, then cranked and started the engine. After about 5 seconds running the blue sensor temperature LED was on steady (okay temp) and the TunerStudio gauge cluster showed the system was operating properly. I cracked the throttle a couple of times to verify the throttle position sensor was operating properly. I ran the engine for about 15 minutes then shut it down.