I have a speed density engine (dodge) with a Baro reading of 27.5 inHG, at my altitude (aprox. 4200 ft above sea level) I usually see a baro of about 25.6 inHG. Now, I am pretty sure I know the answer but need my brain untied from a knot. Would the scenario I just described cause negative fuel trims or the opposite.
"Silver bullets are for killing Werewolves, not fixing Cars." -Rob Longoria-
One of these problems that gets confusing if you over think it.
The engine is at higher altitude than the PCM reads from the sensor so it will want over fuel but in closed loop the fuel trims will go negative to pull it back.
Open loop --- over fuel
Closed loop -- negative fuel trims.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Last edit: 8 years 9 months ago by Andy.MacFadyen.
Andy.MacFadyen wrote: One of these problems that gets confusing if you over think it.
The engine is at higher altitude than the PCM reads from the sensor so it will want over fuel but in closed loop the fuel trims will go negative to pull it back.
Open loop --- over fuel
Closed loop -- negative fuel trims.
Thanks Andy, I needed a second opinion after I made a bad call replacing an aftermarket o2 sensor with a OEM sensor after another tech had used the parts cannon on this truck to fix a misfire at cold startup and then told the service manager it needed valve train work because he "read" it on another website. I knew what I had after I took a closer look at the data, I just needed help with getting past not wanting to make another bad call.
"Silver bullets are for killing Werewolves, not fixing Cars." -Rob Longoria-
