ok i feel like i have a carb here and i have to wait while my car warms up before i can even give it gas...just looking to find out what i should be doing. i use tunercat btw...as soon as i start the car and as long as it is in open loop, if i give it a little gas its ok, but even if i take off 30-40% throttle or if i just tap the gas in neutral, it hesitates. as soon as it hits closed loop, it runs fine, so im figuring its gotta be something i have to tune. what should i be looking at and what tables should i be thinking about changing?

thanx,

Ryan

 

I'm having similar symptoms (poor tip-in response in open loop) after I (1) changed to 37# injectors and (2) let the car sit for several months. Runs great once in closed loop.

I haven't had time to investigate yet. Assuming at this point that I need to play with some of the other injector parameters.

I'll let you know if I figure anything out.

 

Log your fuel trims and see if it is adding or taking away fuel in your 30-40% throttle range.
You probably need to tune for your descreened MAF, but it could also be your injector constants if it only happens at low rpms.

 

as far as logging fuel trims, and correct me if i'm wrong...when in open loop after startup, your fuel trims are going to be locked to what the computer has learned correct? I know when i logged my car the other day my fuel trims were at 128 in open loop (i'm pretty sure they were at exactly 128 because i just loaded a new tune in and the computer hasnt had time to learn much)...but if i run it for a while and the values change when i startup, is that what you are referring to?

and about the injector constants, were you referring to me or steve9899?
i figured if you were talking to me, wouldnt the injector constants affect open and closed loop both?

 

Removed due to proprietary information in which other parties have a secured interest.

 

my problem i wouldnt think of it as a low tps response problem. even if i turn on the car and rev the car up (punch it), it will hesitate until it hits closed loop. once its in closed loop it runs great and the throttle responce is great all around. any other suggestions that might help or do you think the injector thing may help?

i also have questions on 3 other tables (if i should adjust them)

1. %change to fuel/air ratio vs. rpm at WOT
2 Open loop AFR vs coolant temp vs map
3 Initial startup AFR enrichment vs coolant temp

i noticed that in my open loop AFR table, most of the values are 1.5 points higher than stock (i'm assuming this just means its set for a leaner AFR). should i adjust these at all back closer to stock?

thanks again

 

plan z: I have tried modifying the AFR Table and found that the factory numbers are really good so, yes, I would try restoring the table to factory first. I then would pursue the tweaks I mentioned and see if it improves--nothing ventured, nothing gained. If it doesn't improve, just return to your previous tune. Let us know here what you found out. Otherwise, I don't think the tables you mentioned would need to be touched, but if you do, do one at a time and note the difference.

 

Yeah, I bookmarked that thread the other day since it sounded like it might be related to my problem. I'll let you know how it goes. Thanks for that thread BTW.

 

alright thanx a lot again. i'll post up what i find out helped when i get there

 

I was referring to logging your fuel trims when it went into closed loop. If the computer adds/removes fuel (more than a couple of percent), then your MAF calibration is off. With a ported/descreened MAF and other changes to your intake system, the MAF calibration probably is off.
Closed loop operation will clear this up for you but in open loop, it has to use the last BLM recorded for that cell. Depending on how far the tune is out, the LTFT could be different within the BLM cell.
When I mentioned injector constants, I meant the injector offsets.

 

ahh ok, thats what threw me off. i have already adjusted my maf tables quite a bit. the last time i checked (last week), after programming the pcm, started the car, open loop was of course at 128 and as soon as it hit closed loop, i had just a little bit higher values (maybe around 132ish) @ around idle. do you think adjusting the maf tables more around the afgs for idle will help the open loop problem after loading the new tune? also, i haven't been paying much attention to what fuel cell i'm in. what should i be looking at/know about each fuel cell that i'm in?

 

I just saw your other thread. Have you adjusted the AFR vs coolant temp vs MAP table? If so, how much did you adjust the values?

 

yes the "Open Loop AFR vs Coolant Temp vs MAP" table was modified. most of the values are 1.5 higher. the rest of the values are 1 higher. i got one opinion to set them back to stock and another opinion saying i should adjust that whole table by 3-4 higher across the board. what should i do?

 

Well, I don't think you're going to gain a lot of mileage from leaning out the Open Loop AFR table if you're running closed loop, but that's up to you.
Try running the stock Open Loop AFR table and see if it clears up your hesitation

 

heck yea! i think that was it. i put the table back to stock and startup and driving down the street seamed fine. we'll see in the morning if it's the same. that whole article about leaning it out for mileage didnt make much sense to me either, but anyway. i think this cured it...now if my car will only make it through the dyno tomorrow. first time for the 180shot...