rough idle, erratic 02 readings

elturbonitroso · Post by **elturbonitroso** » Tue May 09, 2006 4:49 pm

hi guys like the tittle said i have rough idle and the o2 reading are all over place from 17 to 12 and I try everything change the req fuel nothing and i also try the table transform and no luck at all.any advice what to do .

FoundSoul · Post by **FoundSoul** » Tue May 09, 2006 6:37 pm

Assuming you don't have any ignition problems and your rough idle is purely fuel related I'd get it idling and then using the 3d map (or 2d if you want) you can see what cell need to be tuned-- it sounds to me like you may have a big difference in VE between two columns or rows in the area of the table you're idling in. If that's the case sometimes the engine will 'hunt' bouncing from cell to cell, rich/lean/rich/lean.... If you smooth the cells around idle out you can usually correct this.

Keep in mind the fields are linearly interpolated, so you're almost never running 'exactly' the VE set in a certain field. It's calculated based on all of the fields surrounding the load/rpm point where you are at on the map-- you'll usually adjust multiple fields to correct the idle, not just the one that's 'closest' to where you're idling at.

elturbonitroso · Post by **elturbonitroso** » Wed May 10, 2006 2:52 am

I will try that and i dont think is spark issue since the squirt is only controlling fuel and a msd 6al the spark.

pane · Post by **pane** » Wed May 10, 2006 2:54 am

G'day

I dont suppose that this is a similar problem to mine.

Are you running a v3 board, ms-2 and trying to control a tfi ignition modual?

Cheers

FoundSoul · Post by **FoundSoul** » Wed May 10, 2006 5:18 am

Just an FYI I've got an MS-II V3 board here running a TFI 2.3liter Mustang with a great idle-- rock solid high 13's for AFR at idle, just where we wanted it for best vacuum. We're using the TFI on the input and output, no external ignition box involved.

mops · Post by **mops** » Wed May 10, 2006 12:49 pm

wonky afr's and misfires can be caused by too much or too little timing advance.

elturbonitroso · Post by **elturbonitroso** » Wed May 10, 2006 6:14 pm

i think that was my problem to much timing i put the tmiming back to 10 deg at idle and the car sound much better and wideband is more acurate

mops · Post by **mops** » Wed May 10, 2006 6:30 pm

that sounds good....

idle timing should be between 10 and 15 degrees for most engines I suppose....

you will see that timing too much on the extremes and strange things happen... like unstable afr's/misfires/other interesting phenomena... that apply to all areas of fuel map, not only idle...

elturbonitroso · Post by **elturbonitroso** » Wed May 10, 2006 6:48 pm

yea my timing was at 20 deg since im using a msd 6al to do the timing and ms for fuel but im going to use the ms for both things because i think that i cant run my car all the time at 10 deg.

FoundSoul · Post by **FoundSoul** » Thu May 11, 2006 4:18 am

Static 10 degree BTDC of timing? Wow... are you scaling boost up to like 30+psi to keep the advance needs that low?