throttle hang during cruising
05-23-2020, 12:58 PM
#1
throttle hang during cruising I have this annoying idle hang that I cannot seem to get rid of. It happens when I'm cruising and let off for corners casually and going slow. My idle is set at 800 but likes to hang in the 1500 area. It's real prevalent when coming back or leaving my neighborhood, 20mph zones I just don't touch the throttle and it will idle at 1500 and thats like having cruise control at 20mph. However, when I hit the brakes and the vehicle speed starts dropping the idle will usually try to go back down some but it clearly has a threshold at 2mph. Soon as I go under 2mph and stop the idle drops right to where it should. Above 2mph it will bring the idle down some but not to 800, more like 1000-1500 depending on the speed.
I didnt have this problem before I got the VSS working. I'm using the ABS sensor in a ford 8.8 for the VSS and I had a bad sensor when I started tuning last year. This year I changed the cam, injectors and converter so I had to retune it all and I added the VSS in at that time. It would stall at stop lights and stuff occasionally without the VSS but never had throttle hang. Maybe because the ecu always registered 0mph?
The I sent my ECU off the first time to have a very basic tune installed because I had never used HPtuners before and never tuned an EFI before. So about half of the stuff with zeroed out tables I have no clue what it does and haven't messed with it yet. I did a lot of searching and most of the stuff I found said to check things like idle timing and base timing tables for to much spark in the idle range. I'm at 24* in all the tables for idle on a 231/234 .600/.585 115lsa 5*adv camshaft. Which didnt seem out of the ballpark for it.
Base Idle Airflow is about 14g/s at operating temp. Does the base idle airflow tell the air controller how far to open the stepper motor or it is a relationship to fuel and air like the VE table? I've tried going down 1-2 grams on that table but it didn't seem to help and made it harder to idle while stopped.
Can I use the rolling idle table to fix this? That table has always been zeroed out.
I'm attaching a scan and my current tune. Thanks for looking.
I didnt have this problem before I got the VSS working. I'm using the ABS sensor in a ford 8.8 for the VSS and I had a bad sensor when I started tuning last year. This year I changed the cam, injectors and converter so I had to retune it all and I added the VSS in at that time. It would stall at stop lights and stuff occasionally without the VSS but never had throttle hang. Maybe because the ecu always registered 0mph?
The I sent my ECU off the first time to have a very basic tune installed because I had never used HPtuners before and never tuned an EFI before. So about half of the stuff with zeroed out tables I have no clue what it does and haven't messed with it yet. I did a lot of searching and most of the stuff I found said to check things like idle timing and base timing tables for to much spark in the idle range. I'm at 24* in all the tables for idle on a 231/234 .600/.585 115lsa 5*adv camshaft. Which didnt seem out of the ballpark for it.
Base Idle Airflow is about 14g/s at operating temp. Does the base idle airflow tell the air controller how far to open the stepper motor or it is a relationship to fuel and air like the VE table? I've tried going down 1-2 grams on that table but it didn't seem to help and made it harder to idle while stopped.
Can I use the rolling idle table to fix this? That table has always been zeroed out.
I'm attaching a scan and my current tune. Thanks for looking.
05-23-2020, 01:17 PM
#2
Moderator
Hopefully a more experienced person can guide you to tuning specifics, but look at Idle -> Airflow -> Throttle Follower ->Decay (Gear) values. You might try adding 50% to the values for 3rd and 4th gear to see if that helps.
Yes, the Base Idle Airflow also needs to be correct. 14g/s seems extremely too high; I run 10 g/s with a 7L engine and much bigger cam. A stock 2002 LS1 has values of 6.20. So perhaps try stock values multiplied by 1.25.
I will look at your log and tune later today; hopefully someone can beat me to it.
Yes, the Base Idle Airflow also needs to be correct. 14g/s seems extremely too high; I run 10 g/s with a 7L engine and much bigger cam. A stock 2002 LS1 has values of 6.20. So perhaps try stock values multiplied by 1.25.
I will look at your log and tune later today; hopefully someone can beat me to it.
05-23-2020, 02:28 PM
#3
Hopefully a more experienced person can guide you to tuning specifics, but look at Idle -> Airflow -> Throttle Follower ->Decay (Gear) values. You might try adding 50% to the values for 3rd and 4th gear to see if that helps.
Yes, the Base Idle Airflow also needs to be correct. 14g/s seems extremely too high; I run 10 g/s with a 7L engine and much bigger cam. A stock 2002 LS1 has values of 6.20. So perhaps try stock values multiplied by 1.25.
I will look at your log and tune later today; hopefully someone can beat me to it.
Yes, the Base Idle Airflow also needs to be correct. 14g/s seems extremely too high; I run 10 g/s with a 7L engine and much bigger cam. A stock 2002 LS1 has values of 6.20. So perhaps try stock values multiplied by 1.25.
I will look at your log and tune later today; hopefully someone can beat me to it.
05-24-2020, 12:19 AM
#4
I dropped the base airflow by 2grams and that helped a lot, but also introduced some surging when coming back down to idle. My IAC counts are 80ish when the idle stabilizes. I got the VE corrected for the airflow change. It died on me twice tonight going from drive to reverse.