First Time MAFT Tuning, High Trim Problem.

[joeym4130]

Hi all, I just finally, and happily installed my MAFT 1.3 (plan to upgrade to the new one ASAP) and 3" GM MAF on my 1G DSM. I mounted it on the UICP close to the throttle body. Also installed a new intake pipe, and had to vent my 1G BOV because of this, assuming its ok to do since I have the MAF near the throttle body.

I took it out for a base run, after resetting the ECU, with all the controls zeroed out. Onto the highway, I saw the high fuel trim hit 117.8%. So I went home, reset the ECU again, and put the base knob for the 400CC injectors, in hopes of getting some more fuel.

Was running rich at idle with the new settings so I leaned it out at idle 1 click and got the trim to 98% on the low trim. Went for a 20 min or so drive on the highway and the High trim seemed better at first, but eventually worked its way back up to 117.8% and stayed there.

I was watching the FTO2 value this time, and they would be bouncing around 80-94% at very low throttle and airflow (like 125hz) but once I got to part throttle (180hz or so and up) The FTO2 would bounce around 115%-119%, making my High trim hit the 117.8%.

If I would hardly hit any throttle (like 15% on the TPS) and stayed that way, I could watch my High trim go down, but once I got into a normal amount of throttle while cruising the trim would go back to 117.8

So in short, My low and mid trims are about perfect, but the high is out of control.

I really don't know what to do, being such a noob w/ the MAFT. I don't know where to start looking for problems. I appreciate any help greatly, thanks guys. Hopefully its some dumb problem that I overlooked on my first time out

 

[v8s_are_slow]

1st, the high trim shouldn't be "bouncing" around. O2 trims, yes. high trim, no. it takes a good while for that thing to adjust. but 117% isn't bad unless you're getting knock and having your timing pulled below 15 degrees. don't make adjustments to the high trim too fast cause it'll take awhile for it to move around. also, a good amount of driving on the highway will help to get that one settled in. give it a couple of days to make sure it's where it's suppose to be. if you're still having a problem after a couple of days, get back to us.

on another note, if you're just beginning your tuning, make sure you have your base and aux knobs are where ya want em. once your trims start moving around and you get your base and aux knobs about where they need to be (as close to 100% as you can get them before messing with anything else), adjust the other knobs for the fine tuning.

 

[joeym4130]

Does it really take a couple of days for the high trim to settle, because if i reset the ECU, and go for a drive, it adjusts fairly quickly.

I didnt mean to say the high trim is bouncing, just the o2 trim. But the high trim goes up and down depending on where the o2 trim is at, when driving at 65mph ish. Like in a 40 min timeframe i can see the high trim move a few percents depending on what is happening (ex: high-103%, then i step on the throttle, the ft02 goes to 120%ish, and then the high trim bumps itself up a percent or two)

I went on a six hour drive and stopping to mess w/ the tuning. At the end of the six hours i ended up putting the base setting as rich as i can, and still have a 117% high trim. Its not really knocking, which is nice, but I just dont like the fact that I cant get it to go any lower no matter how rich i get it.

Thanks for the help.

 

[v8s_are_slow]

doesn't always take up to 3 days. but there's been a couple of times that it has taken me that long. talking about just regular driving. is your maft blinking any lights while you drive? i have mine installed in my console and sometimes i'll lift it to make an adjustment and the lights will be blinking a code. everytime it's been blinking though, it's because it didn't read the adjustment i made. i'll usually either flip the switch once and then back again, or i'll try and turn the car off and back on again. usually fixes the problem. if it's not richening up though, and everything is looking good, i dunno why it's staying at 117%. i'd recommend a wideband sooner or later though. but at least if it's not knocking and pulling timing, at least you're good to go there.

 

[joeym4130]

The MAFT looks fine, i have it in the cabin also, and when i make an adjustment I have had the habit of making sure that the light blinks showing that it accepted the change.

Which light blinks when there is a error?

It could always be my MAF, I got it from eBay. Maybe something is messed up with it's readings at part throttle.

Hopefully I'll come across something. Thanks for the help!

 

[joeym4130]

Well, new idea looking at logs, a question hopefully that will be simple.

Is what causes the FT02 to change just simply the voltage from the o2? This is key. I have one of those cheaper OEM replacement o2 sensors in the car, and:

I noticed on a WOT pull, my timing curve looks good, im not knocking, but my o2v is at about .83-.85 max. On my OEM sensor before it pooped the bed, i remember i would get .91 or .93.

Cause I figure, if what changed the FT02 is the voltage, and this newer one is a lower voltage (for some reason) then stock, then the ECU sees that at cruise speeds and increases the FT02 to compensate while the fuel going in is not needed.

?? haha
Thanks!