2nd Gen Non-Engine/Transmission a non Cummins question

[Jim Ross]

What happens if a person unplugs the O2 sensor in an older engine? We have an '89 Ford Bronco, 5. 0 liter engine and AOD trans with the OBD I system. We keep getting an intermittent Check Engine light. Our shop guys replaced the EGR valve because they said the code told them it was bad and that the O2 sensor was OK. We are still getting the intermittent check engine light. I was wondering if unplugging the O2 sensor upstream from the catalytic converter would tell us anything... or will it cause the computer to lean out the fuel mixture?

We only have 1 O2 sensor as best as I can tell, even though the parts store guys' computer shows 2 of them, 1 upstream and 1 downstream from the catalytic converter. I can only find an upstream O2 sensor.

Thanks for any ideas/help.

 

[ToddShepard]

I believe it will go full rich if you unplug it and that can eventually damage the cat. On that old of a vehicle it is a good idea to replace it if in doubt.

 

[jelag]

Most systems have what is called a limp in mode, where when the computer might not see the mass air flow sensor, baro sensor, O2 sensor, etc will go into a program where it cuts back on the HP and goes into a mapped program... .

Less fuel economy, less performance etc... .

Most O2 sensors are $50 or less, its something you should deal with...

 

[DSeamans]

Codes

First off, codes on the older ferds aren't that accurate. They basically give you a place to start looking. No code doesn't mean the sensor is working properly. For example, it can send a low or high voltage that is still within alarm limits and not set a code, but the computer makes adjustments based on that voltage and the results make something else look bad. Take it to someone you trust that has a scanner ( I use my buddy - the chevy mechanic) to read actual voltages from all the sensors. They can tell by watching all the sensors at the same time what is messed up. My kids car kept throwing a code for the o2 sensor and it was the idle air control valve. Good luck.



Dave

 

[Jim Ross]

I replaced the O2 sensor an hour ago, maybe that will solve the issue... . I do know that the economy has dropped off a little over the last 3 or 4 months..... maybe it was the O2 sensor causing the computer to richen the mixture? Driving it and time will tell.
The cost of the sensor was $60 -15% +tax at NAPA.
Thanks to you guys who helped!