Wideband Air/fuel Jumping

Redfire Fox · May 30, 2016

I got an issue with my Wideband O2 reading occasionally spiking. I had my 1991 fox for years and done most of the work. My reading has always been between 12.5 -13.0. Just recently when I start the car I get 14.5 and it stays there till I shut the car off and start it again and it goes back to 12.5. Then I'll drive it and go to the store then start my car and the reading is 14.5?????

It just started doing this and car starts and runs fine. It always stayed at 12.5 till recently.
What is causing this? Should I worry? Doesn't matter if the engine is hot or cold.

mikestang63 · May 30, 2016

Could be a vacuum leak or inlet hose causing a lean condiition. Is the car otherwise running normal?
check the wiring, or your sensor is going bad. I

Redfire Fox · May 30, 2016

The vacuum hose underneath the intake manifold was kinda loose and not pushed all the way in. I'll drive it around and see if that fixes it. Also both my O2 senors were replaced last year.

jrichker · May 30, 2016

A wide band O2 system has it own separate O2 sensors. If you have one the runs off of the stock O2 sensor, it is just another pretty gauge that means absolutely nothing...

The A/F gauges that use the stock engine control computer O2 sensor signal will jump all over the place. The reason is that the O2 sensors "switch" between .2 volt lean and .6 volt rich with a curve that looks like the drop off a high cliff. The curve is almost straight up and down, so the voltage shoots from .2 to .6 and back down . again 2 or more times a second at cruse. You won't get much useful information except when the mixture is extremely lean or extremely rich, there is no middle ground. The engine control computer's program knows about the jumping around . The program is designed to use it to not only measure the A/F ratio, but also diagnose the quality of the sensors and their wiring.

Redfire Fox · May 30, 2016

jrichker said:
A wide band O2 system has it own separate O2 sensors. If you have one the runs off of the stock O2 sensor, it is just another pretty gauge that means absolutely nothing...

The A/F gauges that use the stock engine control computer O2 sensor signal will jump all over the place. The reason is that the O2 sensors "switch" between .2 volt lean and .6 volt rich with a curve that looks like the drop off a high cliff. The curve is almost straight up and down, so the voltage shoots from .2 to .6 and back down . again 2 or more times a second at cruse. You won't get much useful information except when the mixture is extremely lean or extremely rich, there is no middle ground. The engine control computer's program knows about the jumping around . The program is designed to use it to not only measure the A/F ratio, but also diagnose the quality of the sensors and their wiring.

Im using a Bosch wideband 02 sensor on the drivers side with the uego 2000 system. I have a digital air/fuel gauge on my dash and I use the Ford Anderson PMS system to add or subtract fuel and timing.

Well anyway I made a few round trips and the gauge held steady at 12.5 - 13.0 after tightening my vacuum line under the intake manifold. Might be too early to tell if that was the cause of my lean condition.

Noobz347 · May 30, 2016

CrazyRedFox said:
Im using a Bosch wideband 02 sensor on the drivers side with the uego 2000 system. I have a digital air/fuel gauge on my dash and I use the Ford Anderson PMS system to add or subtract fuel and timing.

Well anyway I made a few round trips and the gauge held steady at 12.5 - 13.0 after tightening my vacuum line under the intake manifold. Might be too early to tell if that was the cause of my lean condition.

I would say that it's a pretty good bet that it contributed. Keep an eye out old/loose hoses and replace religiously, particularly if power adder.

12.5-13.0 is very rich if you're not into the boost already or are running pretty high compression. Fully warmed and at idle, the car should be right around 14.7 AFR if adaptive strategies are still operating. Commanded output at warm idle/cruise would be 14.7 with the factory tune.

Redfire Fox · May 30, 2016

Noobz347 said:
I would say that it's a pretty good bet that it contributed. Keep an eye out old/loose hoses and replace religiously, particularly if power adder.

12.5-13.0 is very rich if you're not into the boost already or are running pretty high compression. Fully warmed and at idle, the car should be right around 14.7 AFR if adaptive strategies are still operating. Commanded output at warm idle/cruise would be 14.7 with the factory tune.

12.5-13.0 is great for power at WOT but it is bit on the rich side for idle and part throttle. My car seems to like it though.

Wideband Air/fuel Jumping

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