lummert
Active member
- Joined
- Jan 11, 2008
- Location
- Portland IN
Think my 88 765 TIC has a failed O2 sensor. My fuel mileage average went from 21 to 25 mpg. This suggested something being wrong such as a bad vacuum hose to the FPR which had happened years ago. I tried checking the baseline fuel mixture but could not get the LED to blink, it was steadily lit no matter what I tried.
I then did the O2 sensor tests. O2 sensor output was .8 volts on every test. I tried the tests at 3000 rpm with sensor disconnected and result was still .8 volt. I tried with vacuum hose disconnected and plugged at the FPR, still .8 volts. I tried with a vacuum leak, still .8 volt.
Luckily have have a couple spare O2 sensors handy. But, I'm wondering if I can just run it this way in open loop with the POT screw adjusted to 300 ohms. It starts and runs fine as it is LH2.2. I increased the POT screw setting to make up for the too rich running and will check the fuel mileage average at next fill up.
I then did the O2 sensor tests. O2 sensor output was .8 volts on every test. I tried the tests at 3000 rpm with sensor disconnected and result was still .8 volt. I tried with vacuum hose disconnected and plugged at the FPR, still .8 volts. I tried with a vacuum leak, still .8 volt.
Luckily have have a couple spare O2 sensors handy. But, I'm wondering if I can just run it this way in open loop with the POT screw adjusted to 300 ohms. It starts and runs fine as it is LH2.2. I increased the POT screw setting to make up for the too rich running and will check the fuel mileage average at next fill up.