02WS6FREEBIRD

iTrader: (4)

Car data: 5.7, 224 cam, lt's, 2.5" duals, lid and ported TB

I have been tuning with a wide band and feel pretty good about where the MAF and RAF numbers are at...one time they may be neg. and the next pos. so I have taken an average and most of the time the STFT's are in line, being just a little neg., but every now and then they go either neg or pos. to the point of being 15-20 but the idle and engine runs and seems fine, the car doesn't buck, stumble, etc. What the f@&k is going on...this is driving me nuts. Has anyone else experienced this?

I figure it must be either the readout in hp tuners is incorrect or the O2's sending bad info, but if it was the O2's, wouldn't that make the car run bad?

NoGo

iTrader: (2)

Our cars will run surprisingly well with the a/f ratio way off.

Its probably the tune rather than the O2 sensors. There are alot of corrections that come into play (engine coolant temperature, air temperature, etc...) if all of these tables don't line up, sometimes when the car transitions from one correction to the next the STrims will snap.

My personal opinion is as long as the car is running fine, and the wideband shows the a/f to be fairly close I woudn't sweat it.

Is the car throwing a code or just the STerms are occassionally getting pinned?

02WS6FREEBIRD

iTrader: (4)

Every now and then I get a ses light, I checked the code once and it was something to do with the O2's, I rarely get it though and usually if the drive/scan is 30 min. or longer they always come in back in line.

BlueThunder2

iTrader: (3)

If you tuned your ve and maf tables with the O2 sensors turned off (using nothing but the wideband), and it stayed good the whole time, then I wouldn't worry too much about the tune.

If you tuned with the sensors turned on, and made adjustments to the ve and maf tables by using the STFT vice the LTFT, then it probably needs some more tuning. Those STFT move to quickly to use for data when tuning. The LTFT sets a trend and is a bit more accurate to use.

However, turning off the sensors and using the wideband is really the best method. Then turn the sensors back on when you are done.

NoGo

iTrader: (2)

If you have LT's its not uncommon to throw an O2 code. If the car is running fine, I would be more inclined to off the code rather than chase the idiosyncrasy in the tune that is causing the STFT to momentarily peg.

If you feel like chasing it, chart the commanded a/f along with the STFT. Chart the injector PW and look for step changes. If you see a step change it is probably a table. If everything is smooth check your injector delay curves, the flow vs vacuum curves, and MAF curve. If everything is on spot there, I would look towards the O2 sensors. Watch for long holds in the O2 mV outside of off-throttle and WOT conditions. In these areas you may be able to fudge your VE table or bump the car to open loop to avoid the STRM/LTRM code.

02WS6FREEBIRD

iTrader: (4)

Thanks for the reply's ...

I did not "turn off" the O2's, but did essentially the same thing, tuned with a AEM WB in open loop and I am running only STFT's, LTFT's are off, don't want the bad info getting it to them...

I have seen the trims go to as much as 15-20 off, I would think the car would be bucking like a mule but it runs fine and by the end of the run they have settled down...it bug's me, cause I don't like having something not right and something is making it do it.

NoGo what you said is a little over my head, but I will start doing searches to see if I can figure out what you are talking about...and ...btw...sweeet! HP and Tq numbers.

BlueThunder2

iTrader: (3)

So are you making adjustments by using the afr error data? Where/what tables are you making corrections in?

Nemesis350

iTrader: (11)

I know this is going to sound stupid, but check to see if your maf sensor is clean. I had the same basic issue, except my car was running crappy from a stop; replaced 02s, checked for air/exhaust leaks, etc... then i finally inspected the maf only to find a layer of $#!t across the fins and resistors (whatever they're called lol). cleaned them off with the proper spray, instantly cleared the problem. leveled the ltft (i still have them high, but thats in my tune)

02WS6FREEBIRD

iTrader: (4)

I am using HPT, the main tuning has been the VE and MAF tables, using the error histograms in HPT while using my WB. Also of course I have tuned the RAF table, and made adjustments to the idle tables to help steady up the idle.

BTW MAF is clean and I have a catch-can.

BlueThunder2

iTrader: (3)

O.k., if you haven't tuned with the maf and O2 sensors turned off to adjust the ve table, you might want to do so. (If you are using HP Tuners Pro). It saves a lot of time and trouble. That way the computer doesn't make changes as you are making changes. There is a cheat sheet written up on this on HP Tuners web site. I believe 69Firebird or something like that wrote it. If you would like, pm me your email address and I can email you a copy of it. It has really helped me with my tuning. When I finish cars, their afr is solid for both ve and maf. I highly recommend it over the HP Tuner school method.

Hemi2Slo

Gotta agree with BlueThunder, if you haven't turned your MAF and STFT and LTFT off then your fighting a losing battle trying to tune it. Experience on that talkin here lol.

02WS6FREEBIRD

iTrader: (4)

Update...

It still does this every now and then but the car seems to run fine, no change I can tell to the engine during this, but if I mess with the AFR (I can manually change the afr in HP tuners) if I change it from 14.7 to say 13.7 or 15.7 you can tell the way it runs is off...so I wonder if this is really happening when the stft's are off 15-20? How much AFR is + or - 15-20 on the stft?