Hanging idle at operating temp.
Hello I need some advice on hanging idle when engine is at operating temp. When I stop and shut engine off and come back a few minutes later and restart the idle will go up to 1500-1800 and stay there for about 15-20 seconds before returning to preset warm idle. So basically what I'm saying is you have to sit there and wait for the idle to come down before putting trany in gear (automatic), if not you reak havoc on your drivetrain. This is becoming annoying. What settings should I try to change? should changes be + or - and how much change should I start with. Thanks for any advice.
I had a similar problem, but sometimes it never came back to preset idle. For the sake of it try this. Remove the air cleaner and look down at the butterflies, specifically the secondaries. They may be staying slightly open and then eventually fully close after 15-20 seconds. You can try when your idle is high and manually push the secondaries back to close and see if this returns idle to preset. If it is, you will have to adjust the secondary butterflies via the screw that is on the back of EFI unit on the passenger side. I had this similar issue for a long time and it took a while to figure it out.
You might also check out in Idle Control on your handheld the Loop Rate Down setting. This value controls how quickly it can close the IAC in response to a higher RPM, lowering the RPM quicker. Do a little change at a time to see what effect it has.
Yes, adjust loop rate down. The higher value the faster the decline of the IAC....
What if the loop rate down number goes higher than the loop rate up number to get the idle to come down fast enough for my liking. The factory setting is the loop rate up is higher than the loop rate down. Does this matter? do these settings work independently of each other? As is stands I've raised the LRD by 10 and the LRU by 10 to keep the difference of the two the same as factory setting. If they work independently then I should be able to keep factory LRU setting and only adjust LRD. AM I comprehending this correctly? Tuning these systems is very difficult. Fitech needs to publish a tuning manual for their systems to help users better understand what each setting will accomplish as no two engines are alike. There is a big difference between the tune for a 250 HP engine versus a tune for a 600 HP engine. Just Saying.
Quote from fanof88 on September 29, 2019, 11:19 amWhat if the loop rate down number goes higher than the loop rate up number to get the idle to come down fast enough for my liking. The factory setting is the loop rate up is higher than the loop rate down. Does this matter? do these settings work independently of each other? As is stands I've raised the LRD by 10 and the LRU by 10 to keep the difference of the two the same as factory setting. If they work independently then I should be able to keep factory LRU setting and only adjust LRD. AM I comprehending this correctly? Tuning these systems is very difficult. Fitech needs to publish a tuning manual for their systems to help users better understand what each setting will accomplish as no two engines are alike. There is a big difference between the tune for a 250 HP engine versus a tune for a 600 HP engine. Just Saying.
Only increase the value of loop rate down. They are independent.
Fitech is not a training business. Go look for a Holley carb manual that is written by Holley.... This Forum and a few other outlets are the beginnings of that manual.
Quote from fanof88 on September 29, 2019, 11:19 amWhat if the loop rate down number goes higher than the loop rate up number to get the idle to come down fast enough for my liking. The factory setting is the loop rate up is higher than the loop rate down. Does this matter? do these settings work independently of each other? As is stands I've raised the LRD by 10 and the LRU by 10 to keep the difference of the two the same as factory setting. If they work independently then I should be able to keep factory LRU setting and only adjust LRD. AM I comprehending this correctly? Tuning these systems is very difficult. Fitech needs to publish a tuning manual for their systems to help users better understand what each setting will accomplish as no two engines are alike. There is a big difference between the tune for a 250 HP engine versus a tune for a 600 HP engine. Just Saying.
Please look at my post. I had a very similar problem and it was a mechanical issue with the secondary butterflies. I tried every single setting to no avail. If the secondaries are staying slightly open at idle no matter what parameter you adjust it is not going to fix it. With the idle high, remove the air cleaner and look down the secondary butterflies and force them close with your finger to see if there is movement. You can do the same by pushing the secondary linkage on the side of the unit. If there is movement and the idle goes back to normal when you push on them, then you will need to adjust the secondaries via the screw on the passenger's back side of the unit.