Tuned for 14.7 AFR but goes to 14 when I unplug MVPI?

Maybe is just a coincidence? I am running 1 Bar RTOS tuned Speed Density. When I finished up my fuel adjustments I reenabled closed loop. I left the WB O2 hooked up so I could monitor things. I noticed for some odd reason truck is now running high 13's to 14:1 AFR. I think is odd so I plugged the laptop back in and it started 14.7:1 AFR. I cannot figure out what's up. It seems when I try to log it w/ MVPI hooked up, it goes back to 14.7:1 AFR so I cannot catch it in a log file to trouble shoot. I'm a bit baffled. Any ideas?

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You are logging commanded A/F not actual . Also A/F will always swing some at idle or part throttle

No, I am using a wideband. It was tuned with a wideband and I am logging with a wideband. STFT are giving me 14 AFR instead of 14.7 AFR when I unplug the MVPI and I cannot figure out why. I plug back in MVPI and it shoots up to 14.7 AFR

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Originally Posted by weinerschizel

No, I am using a wideband. It was tuned with a wideband and I am logging with a wideband. STFT are giving me 14 AFR instead of 14.7 AFR when I unplug the MVPI and I cannot figure out why. I plug back in MVPI and it shoots up to 14.7 AFR

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So you are saying the afr gauge is reading different? I would expect the gauge or wiring being the problem causing a voltage issue.

Are you earthing the wideband om the same point as the narrow bands

Interesting question... I grounded it to the accessory power. I could check PCM ground to accessory power and see if there is a load there.

I bet when the MVPI & Laptop are plugged in it's tieing the grounds together with the accessory / WB and the PCM through the OBDII port. Genious, I'd have not thought of that.

I tuned to 14.7 at cruise... and 12.2 at PE

When I unplug the computer PCM goes down by about 1 AFR.