Erratic idle with A/C off after TB install?!?!?!
Erratic idle (mostly) with A/C off after TB install?!?!?! Hi, folks. I just installed a ported & polished throttle body. With the A/C off, the idle is all out of whack. For example, when taking off from a stop in 1st gear, upon letting off the throttle completely at around 1700 RPM and disengaging the clutch, the idle does not return down to normal (1000 RPM or less), instead it either hangs or might even increase (up to 2000 RPM or so). Same when coming to a stop. Idle hangs and won't return to normal until vehicle speed has been at zero for a second or two. With A/C on, the idle behaves much better, but will still hang ever so slightly.
I've researched this somewhat and haven't found anything conclusive. Hopefully some of you PCM gurus will be able to offer some help. Thanks in advance.
[EDIT: At times, it does act up ever so slightly even with the A/C on, but it's still much worse with it off.]
I've researched this somewhat and haven't found anything conclusive. Hopefully some of you PCM gurus will be able to offer some help. Thanks in advance.
[EDIT: At times, it does act up ever so slightly even with the A/C on, but it's still much worse with it off.]
Last edited by RAGEman; Mar 29, 2007 at 06:17 PM.
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Joined: Aug 2005
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From: Sunny London, UK
You need to tune the IAC activity with RAF, Cracker and Follower Im sure is what he means. Do some searching on those terms and all will be revealed.
AC ON changes the amount of IAC airflow which is why that fixes it.
AC ON changes the amount of IAC airflow which is why that fixes it.
Originally Posted by ringram
You need to tune the IAC activity with RAF, Cracker and Follower Im sure is what he means. Do some searching on those terms and all will be revealed.
AC ON changes the amount of IAC airflow which is why that fixes it.
AC ON changes the amount of IAC airflow which is why that fixes it.
Thank you for providing me with at least complete sentences in your response.
Have you ever seen this problem arise after merely installing a ported throttle body with no other changes?
Problem is, I don't have tuning software of any kind except the old Diablosport Predator. And I could be wrong, but I believe RAF, Cracker and Follower are out of its realm of tuning.
Well damn you posted in the tuning section, not the bolt-ons section so this is what you get.
You need to get the the blade screw set properly. It is open too far right now. Since you have no scan tool, you will have to try and repeat until you get it right. FWIW you may not get it right without tuning.
You need to get the the blade screw set properly. It is open too far right now. Since you have no scan tool, you will have to try and repeat until you get it right. FWIW you may not get it right without tuning.
Originally Posted by Frost
Well damn you posted in the tuning section, not the bolt-ons section so this is what you get.
You need to get the the blade screw set properly. It is open too far right now. Since you have no scan tool, you will have to try and repeat until you get it right. FWIW you may not get it right without tuning.
Well, correct me if my mindset is all wrong here, but since I've done the exact same mod on my previous car ('01 Z28) with no problems at all, I don't think I should actually have to do any tuning to fix the problem.
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It's not a paid service and the people here people don't work for you. Your problems are focused around the IAC.
But to get to the point, it depends on a few factors, the port job being one of them. I just tuned a cammed car recently and had it near perfect. About 2 weekends later the guy decided to put on a ported TB. I spent about 2 more hours getting it adjusted and making some idle changes to get it right. Yes the IAC is compensating to bring down the idle. You adaptive idle routines go out of the window once the car is moving. That's why it won't settle down until you stop. If it were mine and I just couldn't find a good adjustment point based on the previous tune, I'd do an RAF assessment and likely end up modifying the throttle cracker table some.
But to get to the point, it depends on a few factors, the port job being one of them. I just tuned a cammed car recently and had it near perfect. About 2 weekends later the guy decided to put on a ported TB. I spent about 2 more hours getting it adjusted and making some idle changes to get it right. Yes the IAC is compensating to bring down the idle. You adaptive idle routines go out of the window once the car is moving. That's why it won't settle down until you stop. If it were mine and I just couldn't find a good adjustment point based on the previous tune, I'd do an RAF assessment and likely end up modifying the throttle cracker table some.
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Joined: Dec 2001
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From: Ft. Lauderdale, FL, USA
Originally Posted by RAGEman
Yes, it stands for idle air control, and yes, my car has it. Thanks for your help. Anyone else have any abbreviations they need help with?
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Originally Posted by Frost
It's not a paid service and the people here people don't work for you. Your problems are focused around the IAC.
But to get to the point, it depends on a few factors, the port job being one of them. I just tuned a cammed car recently and had it near perfect. About 2 weekends later the guy decided to put on a ported TB. I spent about 2 more hours getting it adjusted and making some idle changes to get it right. Yes the IAC is compensating to bring down the idle. You adaptive idle routines go out of the window once the car is moving. That's why it won't settle down until you stop. If it were mine and I just couldn't find a good adjustment point based on the previous tune, I'd do an RAF assessment and likely end up modifying the throttle cracker table some.
Originally Posted by Quickin
The IAC is your problem, thats why I told you check it out.
Most people would have known that was implied by posting "IAC". And I don't mean "check it out" by just making sure someone didn't streal it off your engine. You go figure out why the "IAC" is fucked or not working properly. You didn't know "dick" before, now you have a starting point.
This is what happens when people install mods that give them 2 hp and don't know what else may be affected when they do so.
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