Blackbird

DFCO sure doesn't seem to work for me.

I can't figure out why if I decel in gear the car goes super rich instead of leaning out as it should.

Could this be related to my evap system? This is one thing I have noticed never passes the readiness tests.

I have been trying to solve this mystery for over a year now. Looking for ideas.

Blackbird

nobody?

Patrick G

iTrader: (14)

You can disable DFCO or you can try working at it by trimming your VE table in the cells that achieve high vacuum (15-30 KPa). Most of the time the number is too high and a rich condition occurs.

Blackbird

wouldnt disabling dfco make it worse?

I thought dfco was supposed to cut fuel during decel or off throttle situations?

I was thinking for some reason dfco wasn't working properly on the car, thus this condition???

Patrick G

iTrader: (14)

You can enable DFCO or disable it. Doesn't really matter as long as you tweak your VE tables to whatever you wind up doing.

kp

iTrader: (34)

I have never touched my DFCO or VE table on this 98 and it works as it should, are you talking light decell or letting off the throttle hard, or both?

jimmyblue

iTrader: (11)

Are you saying it goes super rich, by the wideband
or front O2 readings? Or are you saying that because
you see jacked-up LTFT / STFT values?

Blackbird

I am seeing this via my wideband.

Both. Any time I let my foot off the gas in gear it goes rich, it also does it if I throw the car into neutral while rolling. In netrual, at least, after about 10 seconds it will pretty much recover back to 14.7, while deceling in gear though, never. It will go as rich as 10:1 and sit there until I get on the gas again.

It's annoying for 2 reasons. 1. It has to be wasting gas, which does bother me, I do want maximum mileage for my combo. 2. it throws the ltrims so freeking positive that when you get back on the gas it spikes super lean 17:1 at times before settling back in. That lean spike scares me being a FI car. I want to be able to decel and then stomp on it if I want to without worry.

Blackbird

some releveant details.

stock fuel lines, CAS referenced FP regulator, Ractronix pnp fuel pump. Mototron 60# injectors (did it with my Lucas 42's as well) LS6 intake with EGR. 212/218 .522/529 114 cam.

it did it with my blower, does it na, does it with my STS.

Another_User

You DFCO is not cutting in properly because of your modifications. You will need to increase your entry and exit MAP, and you may want to take a look at your entry and exit RPMs. The best way to do this is log your MAP kpa while driving and during decel. Adding about 10-15kpa to each may do the trick. I forget what I added to mine, but it worked perfect.

Ragtop 99

iTrader: (7)

I probably have the same issue. I've had to dial back my VE's at low MAP by as much as 40%. If I coast for bit and then get on it, my STRIM goes way positive.

So I'm looking at the DFCO tables in LS1Edit. In Edit there is a table of MAP v. MPH and 65 KPA is the lowest setting. The KPA is fixed. You can change the enable & disable rpm, and the delay.

Blackbird

it's not VE, scaled it so far back the values are in the teens. no difference, except the car just runs like crap at those loads

is there anything I can scan to verify when dfco is kicking on and off?

i tried a blind stab at adding 10 to the entry exit values as suggested, no dice. I also didn't understand why I would add to the number? seemed like I would want to reduce it???