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Short term fuel trim

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6 years 3 weeks ago #20220 by Fox.b
Short term fuel trim was created by Fox.b
Has anyone ever seen short term fuel trim jumping from positive to negative very quickly (as fast as the Snap-on computer can update, approx every 1/3 of a second)? Pos 5, pos 18, neg 3, pos 23, neg 14.
What could be the reason for this?

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6 years 3 weeks ago - 6 years 3 weeks ago #20232 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic Short term fuel trim
STF closely following the upstream O2 is pretty normal but the numbers seem a little big what manufacturer and engine ?
With STF you have to pick an average value and look at that in relation to the longterm fuel trim.
This the only screen cap I have to hand of STF



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Last edit: 6 years 3 weeks ago by Andy.MacFadyen.

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6 years 3 weeks ago #20242 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic Short term fuel trim
I took this screen shot today it shows how the Short Term Fuel Trim almost mirrors the upstream O2 sensor
B1S1 Voltage output is green trace STF1 is blue trace.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
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The following user(s) said Thank You: Noah

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