Scanmaster weird 02 readings???

[qbano65]

I just installed my scanmaster and BSTC controller today and I'm having a little problem. I was cruisin tonite, I check out my 02 readings and to my surprise I see them jumping from about 750 to about 120, it switched off back and forth, back and forth. Plus my car stalled twice Whats the deal? Oh and by the way I also installed the RJC powerplate. Let me know.
Thanks,
Carlos

P.S> What are some readings I should be getting? Whats average? If you need to know my setup I'll post it.

 

[bruce]

Originally posted by qbano65
I just installed my scanmaster and BSTC controller today and I'm having a little problem. I was cruisin tonite, I check out my 02 readings and to my surprise I see them jumping from about 750 to about 120, it switched off back and forth, back and forth. .

The computer AVERAGES 14.7:1 air fuel ratio when in closed loop so you see the O2's output toggling back in forth from rich to lean.

 

[OKTurbo]

At anything other than WOT the O2 millivolts number SHOULD be jumping around. The computer reads the O2 sensor and is continuously changing the injector pulse widths to maintain the optimum mixture.

Look at your O2 cross counts (cc on the scanmaster)....these numbers should be counting up 10-20 for each "cycle" of the computer. When the cc numbers start slowing down you know your O2 sensor is starting to go out.

As for the stalling....I don't know. Since you installed a power plate you might not be sealing good somewhere and got yourself a vacuum leak. A good check for vacuum leak is to look at your BLM's and INT's on the scanmaster. The BLM/INT "target" number is 128. Numbers higher than 128 mean that the computer is ADDING fuel meaning that unmetered air is getting in (vacuum leak). Conversely...numbers lower that 128 mean that the computer is SUBTRACTING fuel (you're running rich).

Look for a high BLM/INT and let us know. Take a good look under the hood to make sure you didn't knock something loose. Check the vacuum lines on the top of the intake doghouse....these get old and start to crack. Installing the power plate may have done them in.

Good luck and let us know how it goes,
John

 

[qbano65]

Hey guy thanks for the info . I was riding around today and the car didnt stall, the blm/int stayed pretty much around 128, however I never really opened it up. Tonite I'll make a couple of runs and I'll let you guys know how it went tommorow. By the way I still keep getting knock, even sometimes when I'm not at WOT, and the car is running stock boost.

Later and Thanks ,
Carlos