Sensor Question

alright i just swaped out a 4.3 and put in a 5.7L 350 in my 94 Silverado and i have some questions on the sensors. the v6 had 2 sensors that i think are some sort of knock sensors....one on the back of a head and one on the drivers side of the block and the 350 only has one of these types of sensors and the sensors wont reach to the new location...is it okay to cut the sensor wire and add some more wire or will it throw off the computer? Next question is the v6 only had 1 oxygen sensor and the v8 has 2...do i really need the 2nd oxygen sensor?

alright i just swaped out a 4.3 and put in a 5.7L 350 in my 94 Silverado and i have some questions on the sensors. the v6 had 2 sensors that i think are some sort of knock sensors....one on the back of a head and one on the drivers side of the block and the 350 only has one of these types of sensors and the sensors wont reach to the new location...is it okay to cut the sensor wire and add some more wire or will it throw off the computer? Next question is the v6 only had 1 oxygen sensor and the v8 has 2...do i really need the 2nd oxygen sensor?

I am not very familiar with the 4.3 but I am not aware of a knock sensor on the back of the head. Perhaps others can comment.

I assume you kept the PCM from 94 and it only expects one 02 sensor which should be the one before the cat. It would have been in the driver's side exhaust manifold.

You can cut the sensor wire and add wire, this should not affect the PCM as long as you use the same gauge wire.

Good luck.

//2000CAYukon

well the only O2 sensor i have right now is the one just before the cat which is on the xover pipe which is on the passenger side. the o2 sensor i dont have running is on the drivers side exhause manifold.

and i have changed out the PROM in the computer for a 5.7L engine for a 94 so it probably thinks it has 2 02 sensors. so is there any way to run both or 02 sensors or will i get bad gas milage now or what?

I hope adding more wire to the sensor wire wont affect anything so im gonna give that a shot. Hopin for the best right now...

well the only O2 sensor i have right now is the one just before the cat which is on the xover pipe which is on the passenger side. the o2 sensor i dont have running is on the drivers side exhause manifold.

and i have changed out the PROM in the computer for a 5.7L engine for a 94 so it probably thinks it has 2 02 sensors. so is there any way to run both or 02 sensors or will i get bad gas milage now or what?

I hope adding more wire to the sensor wire wont affect anything so im gonna give that a shot. Hopin for the best right now...

My 90 with 5.7 only has 1 02 sensor. I thought that all of the TBIs were pretty much the same. If you wiring harness only has 1 02 sensor, then I don't know how you would add a second 02 sensor. You would have to swap out the PCM and harness for a truck that has 2 or more 02s.

What year truck is the 5.7 from?

//2000CAYukon

The kock sensor wire you can splice.
But hooking up two knock sensos on the 350 pcm chip/pcm may work or may not work.
Also the 350 pcm/chip will be looking for 2 02 sensor reading on the right and left bank.
You may have to run a wire from the other/side 02 sensor into the pcm.
The 350 has 2-02 sensors on each side of engine right?
That change over might get interesting.
Let us know how it goes.
MT

well the only O2 sensor i have right now is the one just before the cat which is on the xover pipe which is on the passenger side. the o2 sensor i dont have running is on the drivers side exhause manifold.

and i have changed out the PROM in the computer for a 5.7L engine for a 94 so it probably thinks it has 2 02 sensors. so is there any way to run both or 02 sensors or will i get bad gas milage now or what?

I hope adding more wire to the sensor wire wont affect anything so im gonna give that a shot. Hopin for the best right now...

Ok I looked at the wiring on both engines.
Leave the 4 wire 02 sensor in the exhust pipe as is.
The 02 sensor in left exhust manifold on the 350 you will need to run a wire from it into pin B-7 on your pcm. You will need the wire end out of a old computer plug in as the 4.3 pcm does not have a wire in there.
On the Knock sensor just wire up the one that is on lower engine block engine
You will not need the one on the back of the head.
But use the 5.7 knock sensor.
Let us know how it goes.
MT

Also the 350 pcm/chip will be looking for 2 02 sensor reading on the right and left bank.
MT

Just curious if you know what year TBI they went with 2 02 sensors for the 350?

I know the Vortec (96+) has 2 or more.

Thanks,
2000CAYukon

If the 350 is out of a '94 unless it has california emissions it only has one O2 sensor. My '94 only has one and, my friends '94 also only has one.

Just curious if you know what year TBI they went with 2 02 sensors for the 350?

I know the Vortec (96+) has 2 or more.

Thanks,
2000CAYukon

I show a 94 eng. K code 5.7 as the first one.
A lot of 96+ may up to 4 of them.
MT

Just curious if you know what year TBI they went with 2 02 sensors for the 350?

I know the Vortec (96+) has 2 or more.

Thanks,
2000CAYukon

I made a mistake on it. I got over into standard transmission set up wiring.
Scratch that info on the 94 5.7 with 2 - 02 sensors.
Sorry about that.

I show a 94 5.7 TBI code K AT transmission only has one in the exhaust pipe a 4 wire sensor.
What year and what trans and what truck sise was the 5.7 engine out of?\
If you are using the crossover pipe with the 4 wire 02 sensor off of the 4.3 V6
Just go with it.
MT

From what i am told the engine came out of a 93 suburban. I dont know what trans. it had in it...

Im going to try making the knock sensor wire longer and see what it does.

I'll keep you guys updated on this good ol project.

Alright the 350 is up and running...it runs really good...no real problems as of now. I'll just have to deal with the "service engine soon" light being on. I believe this is on because the other knock sensor that was on the V6 is not hooked up or mabey i only have 1 o2 sensor. If i get crappy gas milage i'll have to find out how to hook up the 2nd o2 sensor or something. But as of right now i think the 4.3 to the 5.7 swap is a good one...the truck no longer struggles to move itself around...im very happy with this and hope i have no more problems.:evillol:

Ok...I guess it is getting poor gas milage...and i need to know if the 94 silverado's came with 1 or 2 o2 sensors. I also need to know how to hook the 2nd one up since the v6 only ran 1 O2 sensor.

Ok...I guess it is getting poor gas milage...and i need to know if the 94 silverado's came with 1 or 2 o2 sensors. I also need to know how to hook the 2nd one up since the v6 only ran 1 O2 sensor.

As far as I know, all of the Vin K (350) TBI Trucks only came with one 02 sensor.

You should be able to see what codes are stored by jumpering A and B at the ALDL terminal and then counting the flashes of the check engine light.

See http://www.troublecodes.net/GM/ for more details. If the check engine light is on, you are probably running in open loop and the gas mileage will not be as good as closed loop.

//2000CAYukon