I seem to be a step behind in this thread.
but I can't help thinking a quick and dirty way to answer a lot of questions would be to decrease the afr in the idle load and rpm area.

 

Sorry if this is slightly off topic, but:

I have stock injectors, Cosworth cams, and the Buschur Racing Intake, so I have the K&N valve cover filter. I don't have erratic idle during warm up idle, but I do have erratic idle after the car is at operational temp. Would not having a hose coming of my valve cover going to the intake possibly be the culprit? My idle is set to 950 and stays around there about 70% of the time, but the rest of the time it is jumping up to 1200 and then goes down to 600. I also notice the AFRs vary at the different rpm ranges. Any ideas?

 

Ladies and Gentlemen! I am resurrecting this old thread because I am having issues like this also and some things are helping and somethings aren't. Also I am getting the dreaded P0300 about every 40-50 miles so I just drive with it on now! Same problem as last poster (Pegasus). stable while cold then idle fluctuates once o2 kicks in and car is warm. Latencies? Injector scaling? was doing it much worse before I scaled the MAF but now my bottom three numbers in the MAF scale are maxxed out and my LTFT_low is still 12 in Mitsulogger! Finally got the STFT to go from 25 to around 0 at idle. Let me know what everyone thinks. Mods in Sig. Thanks!

Josh

 

It looks like that is your problem right there....maxed out idle LTFT. And, btw the last three values in the MAF scaling table would be for higher airflows, not at idle.

I'm guessing you will need to adjust both latencies and injector scaling. Post up a log of a good 5-10 min idle or tell us what your LTFT Lo and STFT are when idling after warmed up for a good 5 mins.

Then go for a steady 3000 RPM or so cruise for 5-10 mins. Tell us what you LTFT mid and STFT during that cruise.


Eric

 

I think he means "bottom" as in "low", so they are the right ones - for idle. I actually would use the same wording


jmelocik, i believe MAF scaling mostly adjusts open loop operation (cold idle), if your closed loop is erratic i would suggest looking into ICSV values, that set the goal for idle.

 

MAF scaling should affect both open and closed loop ... changing those values changes how the MAF reads the airflow, and therefore how the fuel trims will react since they only reference air flow and lambda from the front O2.

I haven't had much luck with it though and I'm currently tuning a car with pretty much the same issue ... mid trims are around 0 and low trims are around +12 with O2 feedback at +20 at idle and 0 to -8 at cruise.

 

Well what i was trying to say is when you need closed loop idle adjustment, it may be worth to leave MAF scaling aside and adjust idle settings instead.

And as i believe i posted in this thread - my personal experience with open loop idle tweaking through MAF scaling was pretty successful.. My idle is right around 14.7 and steady with stock timing and HKS280 on start up in any weather.
Although my trims may be off as well now, i haven't had time to get to that yet. But then again - i have to deal with changing E85 blends, so fluctuating trims do not concern me, as that's what they are for - make adjustments to fueling, so i don't have to.