1 wire to 3 wire O2 Sensor

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CrustyJunker

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Another vote here for tapping off the fuel pump relay. Only reason is in case you have to do diagnostics or anything that's in extended key-on/engine-off situations. I don't know how tough the AFS74 is, but some sensors can be thermally shocked if left in one of those super hot conditions without exhaust flow. They can handle the heat, but a few spittles of raw fuel or water vapor immediately/shortly after initial startup can zap a sensor (at least the heater part).
 

351FUN

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Is this something worth doing with stock manifolds? I want to replace the sensor anyways since the truck has 250k and the sensor may too, but it seems like a worthwhile upgrade.

Exhaust past the manifolds is 3" through a Borla xs, and I plan to replace the Y soon, but I have no plans to ever do headers.
 

rockymtnlover

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After a few tanks through it I'm confident in saying that I've got about a 2 avg mpg increase from 12 to 14... a lot of my driving is ~25mph on dirt roads.
I tapped into the fuel pump relay to power it.. I do have headers, upgraded Y pipe and 3" exhaust.
 

JCribb

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I’m going to do this conversion on my 89 4.3 c1500. The rich smell is excruciating, and it doesn’t do as well as I thought it would mpg wise being a stick shift and two wheel drive.

The links on the first page are still valid and reasonably priced, I think $45 and $17 for the sensor and connector.
The only other retrofit I saw, was from the 3rd gen Camaro forums using Casper electronics at $85.
 

Schurkey

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I’m going to do this conversion on my 89 4.3 c1500. The rich smell is excruciating,
That's probably telling you that the catalyst has failed.

A new O2 sensor is a good idea, but also be looking for misfire. 'Course, at the age these trucks are, the catalyst MAY have died a natural death.
 

JCribb

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That's probably telling you that the catalyst has failed.

A new O2 sensor is a good idea, but also be looking for misfire. 'Course, at the age these trucks are, the catalyst MAY have died a natural death.
I replaced the whole exhaust because it did. New y pipe and all. Put the old sensor in, I’m thinking it’s been long gone for quite some time. Truck has over 330k miles.
 

Treble

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did you check to see if the fuse is hot even with key off? i have seen the fuel pump fuse on battery voltages. I splice into the NC side of the fuel pump relay. this way the heated O2 ONLY gets power when the vehicle is RUNNING. On the '92 gmc I just did, this was the grey wire off the relay. the fuel pump fuse did not have battery voltage in this instance.


tayto.... Can you post up a few images of how you spliced into the gray wire?


Trying to figure out the best way to run this.
 
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