93 5.7 cat delete o2 sensor light

[ol-Betsy]

I have a 1993 k1500 and the cat has fallen apart and no longer existed within the exhaust. It has some rust and leaks so I had a straight pipe put in place. I put a new O2 sensor in (OEM ac Delco) and the ecm isn't having it. Still throwing a light. It runs good but I'm afraid it's in limp or running rich. This truck only has 1 factory O2 sensor, and it was pre-cat. My understanding is it's used for fuel trim then so she can't be running right.

I'm looking to not spend the money and replace the cat. What are my options to not only get rid of the service engine light but to more importantly correct the fuel trim, leaving the exhaust at its current state?

 

[GoToGuy]

Did you clear the existing codes? Did you text to see if the O2 sensor is functioning?

 

[ol-Betsy]

Did you clear the existing codes? Did you text to see if the O2 sensor is functioning?

I did clear the codes. O2 sensor has power- I'm not sure how to check that it functions with it being OBD1

The weird thing is I put almost 100mi right after I installed the sensor before the light came on. At that point the cat back exhaust was off the truck. Once I finished welding the y pipe flange and connected the exhaust, the light started coming on after no more than every 10mi.

Correct me if I'm wrong, but the truck will always throw a code for an upstream sensor if the cat is gone right? Meaning the problem is that the cat is missing rather than a bad sensor.

 

[Nad_Yvalhosert]

Correct me if I'm wrong, but the truck will always throw a code for an upstream sensor if the cat is gone right? Meaning the problem is that the cat is missing rather than a bad sensor.

You're wrong. The Upstream O2 sensor has no idea that the catalyst is present or functional.

You need to correctly diagnose the code instead of loading up the parts cannon.

 

[PlayingWithTBI]

I did clear the codes. O2 sensor has power- I'm not sure how to check that it functions with it being OBD1

Put a scanner on it, not a code reader, and look at O2 Voltage (~0-.95V) feedback. Below .45V means it's running lean, >.45 means it's running rich. Then look at "Cross Counts", meaning how many times it "Crosses" back and forth over .45V. Yes, OBDI can do all this stuff.

If you have a 1 wire sensor, it may not be getting hot enough to work, due to less back flow restriction. A heated 3 wire will work better.

 

[ol-Betsy]

Put a scanner on it, not a code reader, and look at O2 Voltage (~0-.95V) feedback. Below .45V means it's running lean, >.45 means it's running rich. Then look at "Cross Counts", meaning how many times it "Crosses" back and forth over .45V. Yes, OBDI can do all this stuff.

If you have a 1 wire sensor, it may not be getting hot enough to work, due to less back flow restriction. A heated 3 wire will work better.

Awesome thanks for clarifying. I'll have to get my hands on an obd1 scanner and check the readings. I did get the 3 wire heated sensor for that exact reason.

 

[ol-Betsy]

You're wrong. The Upstream O2 sensor has no idea that the catalyst is present or functional.

You need to correctly diagnose the code instead of loading up the parts cannon.

Loading up the parts cannon? I haven't replaced a single part since the code popped up. But thank you for your point about the upstream sensor. This is good news for me then considering I don't want to change the exhaust.

 

[someotherguy]

Uncorking the exhaust by deleting the cat may have caused the O2 sensor to be a bit too sensitive. A trick some have tried with success is spacing the sensor out of the exhaust flow a bit with a spark plug non-fouler. I've never done it, but have seen it mentioned here and other forums quite a bit. A very inexpensive thing to try, anyway.

Richard

 

[Nad_Yvalhosert]

Uncorking the exhaust by deleting the cat may have caused the O2 sensor to be a bit too sensitive. A trick some have tried with success is spacing the sensor out of the exhaust flow a bit with a spark plug non-fouler. I've never done it, but have seen it mentioned here and other forums quite a bit. A very inexpensive thing to try, anyway.

Richard

The non fouler is for downstream sensors, not the single upstream in a TBI. O.P. has a '93 OBD1 vehicle... (per title and post #1)

The use of the non fouler is to sample less of the gasses. And the upstream O2 needs as much flow as possible.

If you extract the sensor from the uncatalyzed exhaust flow you will send erroneous data to the ECM sending the fuel trim out in left field.

 

[someotherguy]

The non fouler is for downstream sensors, not the single upstream in a TBI. The use of the non fouler is to sample less of the gasses.

O.P. has a '93 OBD1 vehicle... (per title and post #1)

If you extract the sensor from the uncatalyzed exhaust flow you will send erroneous data to the ECM sending the fuel trim out in left field.

Fair enough. Like I said, I haven't done it. Truth is when my cat rattled itself to death on my '94 5.7 it never set a code. That was a heated-O2 truck. Come to think of it my '92 5.7 cat came apart as well, and the non-heated O2 didn't set one either.

Richard