Idle hunt/dip on coast
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Idle hunt/dip on coast I installed a new motor in my 2000 camaro and had it dyno tuned. Now im trying to get the street manners a little better. When coming to a stop it will hunt for an idle. Usually bouncing between 1000-1500rpm, but sometimes it will dip down to 400 and stay there a bit while it tries to fight back up to idle of 975. It usually dips when im braking and turning at the same time or braking hard. I have hp and can post scans but i dont even see anything that screams "this is wrong". Help please
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From: Monroe,NY
Is it a manual or auto? Your base running airflow is probably wrong and or you may have to play with throttle follower or throttle cracker but make sure your base running airflow is correct first. There is a Russ K idle config that gets your idle airflow perfect.
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Its a manual and im thinking that as well but i dont know if stit are based off of MAF reading or not and i dont have my MAF tuned. It shows that i have my RAF set very high and i have done the russ k config and lowered the RAF but it didnt really help. Ive read that if its too high you get a "cruise control" effect so maybe i should try going up in it next chance i get and see how the car responds. Im doing it in rtt so it souldnt take long
Isn't there a screw or nut or bolt on the throttle body or Idle control motor that you can manually adjust so that more air enters the engine at idle?
What you ideally want is for 90% of the hot-idle air to enter the engine through the manual adjustment, if there is one. That way the idle motor only has to bring it up 10% and that leaves WHOLE REST of it's capacity/range to raise the idle for cold starts and other situations which call for it.
For example, if your target idle warm closed loop is 850rpm,
You would set the manual airflow for idle to about 790-810rpm, with the idle motor at 0% open (disconnected/closed). Then, plug in or re-activate the idle control motor so that it can bring the rpm up that last little bit.
What you ideally want is for 90% of the hot-idle air to enter the engine through the manual adjustment, if there is one. That way the idle motor only has to bring it up 10% and that leaves WHOLE REST of it's capacity/range to raise the idle for cold starts and other situations which call for it.
For example, if your target idle warm closed loop is 850rpm,
You would set the manual airflow for idle to about 790-810rpm, with the idle motor at 0% open (disconnected/closed). Then, plug in or re-activate the idle control motor so that it can bring the rpm up that last little bit.
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My IAC are at between 60-80 at idle which was about the best i could get it. I am running an OL SD tune right now. Already had it dyno tuned. Just trying to get the last bit if drivability issues worked out and then im going to try to get my MAF tuned and working again
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You need to log all of the idle stuff.
Setup follower for return to idle.
Setup cracker for rolling idle.
My car was a 2000 6 speed car (auto now) and did the same thing you're describing. The problem is slow speeds when you are below the cracker speed and since you're rolling no adaptive idle. I was able to add Idle->RPM->proportional airflow to correct the problem.
Setup follower for return to idle.
Setup cracker for rolling idle.
My car was a 2000 6 speed car (auto now) and did the same thing you're describing. The problem is slow speeds when you are below the cracker speed and since you're rolling no adaptive idle. I was able to add Idle->RPM->proportional airflow to correct the problem.
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Well i spent hours playing with the cracker and follower and couldnt really get anything other than a hanging idle. I then decided to add into the primary VE where it was dipping into, mostly 50-65 kpa and 400 and 800 rpm and it seemed to help. Didnt swing nearly as much when it was hunting and i couldnt get it to dip below 800rpm. Ill mess with it more tomorrow and try to see exactly which cells are having the most effect.
ok Ill try again. The minimum amount of air entering the engine is often set by a mechanical screw or adjustment ****, somewhere on the engine (not all engines but yours might). This has nothing to do with computer tuning. You set that adjustment **** so that the MINIMUM RPM that the engine is able to EVER achieve during a HOT IDLE is just below the computer control set point. That way the idle will NEVER drop below that point, coasting, lifting, idling, whatever.
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I think i need to go back to the beginning because i have gotten a little bit away from where my tuner gave it to me. I added spark to get rid of bucking at low input/low rpm but still have the closed throttle while rolling rpm hunt. So what make up desired air flow. I know its a calculated value. When i got my car from the tuner my raf at temp was 14 but when i run the config it says it should be 9.8. Thats a big difference. I have my Maf failed and unpluged so its reads a flat 3g/sec at all times in the scanner.
I've been tuning engines since 2001, over 100+ engines for sure, and every single one of them is the same: they use airflow to set the minimum idle speed, and 99/100 of those engines have had an adjustment on the intake manifold or IACV or throttle body to set that minimum airflow value. NOT ALL TUNING Is done with the laptop! Busy smashing your head into the keyboard when you should be turning a damn screwdriver!
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The car does not dip down past idle anymore, sorry for the confusion. I adjusted my idle screw and got my iac down to about 50. Now i just am chasing a rolling surge where it bounces between 1000 and 1500rpm sometimes. At this point im curious about the RAF table and why when i run the config everyone uses it says i need significantly less than what i was set it when i got my car back from my tuner. Pulling that air out brought down my stit from -10 to -0.5 but i really didnt notice any difference in drivability
What I found was my idle controller was picking up cam surge, and derivative air was kicking in "anticipating" the need to add or cut air, and causing surge.
From 0.00 to 0.05 columns I put in zero.
Next column 1.75
2.00 in all other columns.
Both under speed and overspeed. Really stabilized the IAC motor.
Worked in mine anyway.
From 0.00 to 0.05 columns I put in zero.
Next column 1.75
2.00 in all other columns.
Both under speed and overspeed. Really stabilized the IAC motor.
Worked in mine anyway.
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Thanks for the help, just looking for what to try next. Ive tried cracker settings(zero out to see if it was causing a problem) added timing, took out timing. I also keep playing with my raf. Not sure if i should pit it back to where is started. Thats why i was asking about the raf config and desired airflow.
Gotcha. Without really giving it a good look over, I don't have any good advice for where to set RAF. Generally I've found if it's trying to dip it's not a good idea to cut base airflow
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From: Monroe,NY
Looking at your log when your idle dips your fuel trims go really rich. Your 400 rpm in your ve table is quite a bit lower than your 800 rpm . I would get them closer. I think when it starts to get around or below the 800 rpm range it starts to drop off quick causing your dip in rpm. Just something to try.
Here is a good right up for idle tuning. http://www.hptuners.com/forum/showth...ures)&p=271136
Here is a good right up for idle tuning. http://www.hptuners.com/forum/showth...ures)&p=271136