O2 Sensor Testing

[Mango]

Can you test a Single Wire O2 Sensor with Multi Meter in OHMS

 

[Ricko1966]

Check voltage if it's on the bench heat it with propane watch voltage rise and drop with heat,look for slow or un responsive.on the car in voltage mode check your voltage,create a vacuum leak to make it lean,watch your voltage,cap your leak spray some carb cleaner in the air cleaner,drive it rich watch your voltage. Again look for slow or unreponsive.

 

[cfj610]

Rick - By your comment above, it looks like you may be able to help.
I upgraded a GREAT running 87 R10 (2WD) 305 to a 350 and have had rich fuel issues ever since. Only other additions is the mild RV Cam and Headers

We "think" it's running rich due to the single wire O2 Sensor being installed just behind the headers on the drivers side causing the sensor to not see enough heat and operate properly since it's not near the motor where it belongs.

My question is: is it possible to install an incorrect resistor on the end of the O2 wire faking an incorrect reading resulting in allowing the computer to lean the fuel ratio and run better?
(and plug the bung). And if this DID work, would it likely run poorly until warmed up?

I'm totally spitballing at this point and running out of ideas. Also looking at installing this Stage 1 Computer Chip Module https://www.summitracing.com/parts/JET-28703
Any advice is appreciated and Thank You!

 

[Ricko1966]

Rick - By your comment above, it looks like you may be able to help.
I upgraded a GREAT running 87 R10 (2WD) 305 to a 350 and have had rich fuel issues ever since. Only other additions is the mild RV Cam and Headers

We "think" it's running rich due to the single wire O2 Sensor being installed just behind the headers on the drivers side causing the sensor to not see enough heat and operate properly since it's not near the motor where it belongs.

My question is: is it possible to install an incorrect resistor on the end of the O2 wire faking an incorrect reading resulting in allowing the computer to lean the fuel ratio and run better?
(and plug the bung). And if this DID work, would it likely run poorly until warmed up?

I'm totally spitballing at this point and running out of ideas. Also looking at installing this Stage 1 Computer Chip Module https://www.summitracing.com/parts/JET-28703
Any advice is appreciated and Thank You!

Put a 3 wire sensor in it,the other 2 wires are for 12v to heat the O2 sensor. Anything that changes vacuum,changes what the map sensor thinks is going on. Check your vacuum at idle,and make sure the engine is timed correctly.

 

[gmbellew]

did you put in the correct PROM for the new engine in the ECM? if not. I'd start there. going from 305 to 350 and not changing thr PROM could cause all sorts of issues.

 

[Ricko1966]

did you put in the correct PROM for the new engine in the ECM? if not. I'd start there. going from 305 to 350 and not changing thr PROM could cause all sorts of issues.

I thought 305 and 350 used same prom different injectors 305 would be rich with 350 injectors. But with headers and I assume duals and A 1 wire far from the engine the o2 is never going to get hot and he's going to stay in open loop.

 

[gmbellew]

As far as I know PROMs are engine specific. Might be close enough to run, but certainly not as well as if the PROM is correct for the engine. TBI can only compensate so much

also depends on if the injectors were swapped to 350 injectors, or if the 305 injectors were used.

if a 350 was swapped in, 350 injectors would be recommended with a 350 PROM for the best chance at running properly. any other random combination of 305 and 350 parts/PROM would certainly have some issues with fuel delivery, I'd think.

he can check for open or closed loop by jumpering A and B on the ALDL while the engine is running. the check engine light flashes every 2.5s in open loop and every 1s in closed loop. check it when the engine is good and warm. it's called field diagnostic mode.

I thought 305 and 350 used same prom different injectors 305 would be rich with 350 injectors. But with headers and I assume duals and A 1 wire far from the engine the o2 is never going to get hot and he's going to stay in open loop.

 

[cfj610]

Thanks Fellas!!! This is great data to share with my mechanic!
I truly appreciate your time and sharing your knowledge