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Old 04-17-2007, 11:27 PM   #1
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Default All systems go

well I had a buddy who got a ls1m come over and we did some scans. she is healthy so I am going to take her to the track and see how she does. just curious if o2 is just a mpg thing not a engine variant because the o2s are good when on the gas but on cruise and off the gas they are crazy.
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Old 04-17-2007, 11:39 PM   #2
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Please elaborate...
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Old 04-17-2007, 11:44 PM   #3
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yeah they do do more then mpg though
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Old 04-17-2007, 11:46 PM   #4
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Ok, I'm totally lost what you guys are talking about
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Old 04-17-2007, 11:58 PM   #5
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Default Re: All systems go

Quote:
Originally Posted by gojo83
just curious if o2 is just a mpg thing not a engine variant because the o2s are good when on the gas but on cruise and off the gas they are crazy.
What you are seeing is perfectly normal. Your scan tool or the O2 sensor isn't screwed up.

What is happening is this:

1.) The O2 sensor is slow to react, it always lags behind. A heated O2 sensor comes online a little quicker, since it doesn't rely on the exhaust gas to heat it up to it'* operating temp. But both are slow to react to changes in oxygen content in the exhaust.
The ECM isn't screwed up by this, the software in it already knows when to ignore the O2 readings because the engine temps are not up to the operating range yet.

2.) At very low RPM (idle), you can see the individual pulses of hot gas going past the O2 sensor, so the "frames" of data being given to the scan tool are catching the gaps, so it apears the O2 values are all over the place. This doesn't screw up the ECM either..it sees the O2 values many more times than it'* reports to the scan tool via the serial data connector.

3.) At cruise, the ECM intentionally cycles the mixture rich-lean-rich-lean... This is done to oxygenate the catalytic converter'* brick..leaving enough free oxygen in the cat to react with the hot exhaust gas. This is why the 3800 motor doesn't employ an air injection pump...the ECM is adding oxygen to the cat on it'* own via the mixture. This also doesn't screw up the ECM...it'* software is intentionally doing this and knows what it should see on the O2 sensor during these cycles.

End result is you will drive yourself nuts trying to follow O2 readings. The only time you look at O2 values is during WOT acceleration..a state when the ECM goes into power enrichment mode and stops cycling the mixture. At less than WOT, look to the BLM and Integrator values to see how the ECM is reacting to the engines mixture. A 128 score on the integrator and BLM is perfect...the ECM is computing a perfect injector pulse without having to add any additional adjustment to the calculation.

To simplify this a little..Integrator is "short term" adjustment. What it means is that based on the last couple of readings of the O2 and other sensors, by the ECM, the ECM is going add or subtract the integrator from the computed pulse width.

BLM ("Block Learn Mode") is the long term adjustment...if the ECM keeps having to adjust the integrator over a few cycles in the same direction, then it will add to the BLM to shift the whole pulse width calculation in that direction.

Both are 1 byte variables in the ECM...minimum value is 0, maximum is 255, right up the middle is 128. The closer the integrator and BLM stay near 128, the better the match between the tables used to calculate the fuel injector pulsewidth are to the actual motor the ECM is controlling.
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Old 04-18-2007, 12:42 AM   #6
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Old 04-18-2007, 03:22 AM   #7
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Your second scan has no O2 data.

(But it'* got lots of WOT KR!)
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Old 04-18-2007, 03:41 AM   #8
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could the KR be from a clogged cat or something like that
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Old 04-18-2007, 07:52 AM   #9
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Something to mention here.

At idle and crusing under low load conditions you should see the O2 toggling high/low or rich/lean reasonably quick. If not..your O2 is lazy and costing you MPG'*.

At WOT the O2 should lock in up on the rich side as you are pushing tons of fuel into the motor for more power.

The KR could be a mutitude of things. Try a tank of premium fuel and another scan. It could also be caused from needing a tune up etc. When was the last tune up?
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Old 04-18-2007, 08:03 AM   #10
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Quote:
Originally Posted by gojo83
could the KR be from a clogged cat or something like that
Hard to say. Like the fellow said, your second scan (where you went WOT from 60 to 70 mph) did not contain any O2 data, which is what you would want to look at during a WOT pass.

First scan, just tooling along at a steady 1500 rpm, looks perfectly normal. O2 values bouncing around from the ECM cycling rich/lean, no KR, reasonable BLM.

If you still have the raw data, put up the same scan data, but with the same fields on the secend scan as are on the first one.
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