Idle Hangs after getting to operating temperature
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Teching In
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Idle Hangs after getting to operating temperature Just like the title says, my idle will hang between 2000-3500 rpm after getting to operating temps with just tapping the throttle. I have replaced the IAC, TPS, and I haven't found any vacuum leaks. I am attaching my tune to see if anyone can find anything wrong with it. Also my IAC counts go to zero when it gets to around 170 degrees.
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From: Katherine N.T Australia
Whats timing dropping to when you get off the throttle. I can't read your tune, but if its still hanging around above 30º thats your problem. Id also say you've got to much air with IAC at zero.
[edit] just downloaded HPT and had a look.. As I suspected way to much idle timing. Revert it back to stock and go from there. Also your desired air is way to high. Do a RAFIG pass on it to get it right.
[edit] just downloaded HPT and had a look.. As I suspected way to much idle timing. Revert it back to stock and go from there. Also your desired air is way to high. Do a RAFIG pass on it to get it right.
Last edited by macca_779; Jan 10, 2014 at 07:08 PM.
Thread Starter
Teching In
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The tune I have is whatever the previous owner did to the car. It has a Comp Cam XR 281-hr 112. I didn't start having this issue till about a month before I deployed. The previous owner also drilled the throttle blade to.
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From: Katherine N.T Australia
Dial in the desired air and lower the base timing to stock and see how you go
which doesnt need a hole in the TB....(there are reasons to drill... that cam is not one of them)
usually you only need to drill with a Big cam and its to preserve the off idle throttle transitions as moving the TB blade changes that relationship and can cause some transitional fueling issues
the TB hole/Tune is not necessarily the issue.... if it idled fine and then suddenly one day it changed...then you have sprung a leak...
Last edited by soundengineer; Jan 13, 2014 at 01:23 AM.
also, Timing around 30* at idle is not an issue
many LSx cams love to be around 28*(+/- several degrees) at idle....and have +/- 15* either way to control idle by timing changes(faster than IAC)
many LSx cams love to be around 28*(+/- several degrees) at idle....and have +/- 15* either way to control idle by timing changes(faster than IAC)
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Launching!
Joined: Oct 2012
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From: Canada
Lets say you dont find a leak, it does sound as if you do though.... If your IAC counts are hitting 0 then more than likely the TB has been drilled too large, but something to check before you go changing the TB to correct this. Have a look at the throttle blade in the park position, if it appears that the previous owner had opened the blade to any extent via the set screw, close that up, set the throttle blade back to it original park position, fully closed. Then reset the TPS and see if the IAC counts come to a more normal range at idle. If closing the throttle body to a real life value of 0 does not net you in a more reasonable IAC count then I would replace the throttle body and do it right. But, as I was getting at, if you check and the throttle blade is at a real position of 0 right now then I would replace the body and retune it.
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Joined: Oct 2012
Posts: 258
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From: Canada
If you are looking for a leak, an oldie but a goodie... a can of brake cleans is your friend. There are a couple different ways to do this I know, but being a 3400V6 driver for 13 years I know all about intake leaks!....lol They are horrible for it, anyway, spray any connections after the Throttle body and around the intake with shots of brake clean while scanning and listening closely to your idle. When/if you hear/see in scanner the idle jump you have found it. It's how I have many times diagnosed intake leaks in the past in all types of engines and platforms
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From: Katherine N.T Australia
Logging short term and long term idle airflow trims in one PID that generates a correctional error for you to apply to the desired airflow table. After doing this learning (ie trims) become somewhat unnecessary. As the table is dialled in
But it's critical you also have appropriate timing at idle. (Stock is a good start) Not 30deg like some people believe as you have to have enough base airflow so that timing can do the majority of the work with rpm returning to idle quickly, not hanging, not hunting and not stalling. I can get a 240's cam to idle at 900 rpm with no hole and stock like manners. So it's possible
Your problem is probably an air leak though as it's a new problem. Check your PCV lines. The T piece at the back and the rubber just after the valve are common failures. But still I can see you idle values could use some attention to improve drivability.
If you want more than just my word for it read this. Page 94
http://books.google.com.au/books?id=...banish&f=false
Last edited by macca_779; Jan 13, 2014 at 03:00 AM.
