Cause of AFR going rich at WOT?

I had my car tuned last summer after putting a 2.8 pulley and JLT intake on it, it has been running great until recently. I noticed while doing a couple WOT Pulls the AFR goes to 11.7, which is where it was tuned at, then AFR goes rich to like 10.0

Its never done this before usually it hits 11.7 at WOT and stays there till i let off. Any suggestions to what would cause this to happen?

What kind of gauge? Try recalibrating it?


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Did you adjust it a couple points leaner or richer in the handheld? Probably your Wideband


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I have an AEM Failsafe gauge and wideband. I replaced the sensor thinking that it might have been that but there was no change.

On my SCT handheld i can monitor several sensors and one i was watching was the pressure drop across injectors, I noticed that this was jumping around alot. It jumped to 50psi then down to 25psi then back up and down several times when I went WOT then stabilized around 70psi. My fuel system is all stock with a new fuel filter and FRPS. Is that normal for the pressure to jump like that?

88stangnut said:

On my SCT handheld i can monitor several sensors and one i was watching was the pressure drop across injectors, I noticed that this was jumping around alot. It jumped to 50psi then down to 25psi then back up and down several times when I went WOT then stabilized around 70psi. My fuel system is all stock with a new fuel filter and FRPS. Is that normal for the pressure to jump like that?

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If you are at WOT......no your pressure should not bounce around like that. If you are on and off the throttle then yes that is normal.

--Joe

What's your fuel pump duty cycle at?
I hit .99 (99%) with just a 2.8 pulley and supporting mods. Solution was a BAP. Now I rarely see over .80 fwiw.