Hanging idle after LS6/TB install
06-24-2011, 08:03 AM
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Hanging idle after LS6/TB install I just did an ls6 intake swap last night and removed the AIR/EGR. Also installed a P/P TB. Started the car and it idled fine, however, when I start to drive it will idle between 1800-2000 RPMS until I come to a stop and then it will come down. We checked the TB blade and cable to make sure the blade was closing all the way. There is a little tiny hole in the middle of the blade that if you put your finger on it the idle will drop down to about 500. Thought this might be a cause and there is simply too much air flowing through. I can hear a small exhaust leak from one of the block off plates. Im not sure if an exhaust leak would cause an idle like that though. Vacuum leak would make the idle hang all the time correct? So I am torn between either it being in the tune itself (Stock) or there is some sort of leak, MAF sensor or the TB itself. The car runs perfectly fine. I am taking it to the tuner next Wednesday, but if there is anything I can try to resolve the idle before that would really be nice for my neighbors lol.
06-24-2011, 08:50 AM
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Most common culprits would be the throttle blade not at 0% or completely closed/flat. Adjust the idle screw to make sure it is in fact closing completely.
Could be too much porting was done on the throttle body and letting too much air by the blade...somewhat less common.
Also do the TPS relearn procedure once you know the throttle blade is indeed closing to completely flat or 0% throttle. Unplug TPS and turn the key to on but do NOT start the car. leave for 30 seconds. turn key off. plug TPS back in. turn key to on again. This should make the TPS see wherever the throttle blade is at to be 0% throttle.
Could be too much porting was done on the throttle body and letting too much air by the blade...somewhat less common.
Also do the TPS relearn procedure once you know the throttle blade is indeed closing to completely flat or 0% throttle. Unplug TPS and turn the key to on but do NOT start the car. leave for 30 seconds. turn key off. plug TPS back in. turn key to on again. This should make the TPS see wherever the throttle blade is at to be 0% throttle.
06-24-2011, 09:05 AM
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10-4. We did check the T/B and adjusted the cable before we put the lid back on it. Ill double check it this evening and do the idle relearn.
The T/B was ported really well. Ill snap a pic of it tonight, but I think that could be the culprit. The tune should fix that correct? I was thinking of trying to plug that little hole in the middle of the blade temporarily to see if that will releive the high idle until I can get it to the tuner next week. I am scared of doing that though as I dont want to suck anything down into the intake.
On a better note. The throttle response and higher rmp performance is great. At first I didnt notice any difference, but on my way home I hit it hard from 3k 1st through third gear and felt it. Cant wait to see what the tune does. Car also sounds different. I imagine that is due to the lack of AIR/EGR and more air flow. Definitely got louder.
The T/B was ported really well. Ill snap a pic of it tonight, but I think that could be the culprit. The tune should fix that correct? I was thinking of trying to plug that little hole in the middle of the blade temporarily to see if that will releive the high idle until I can get it to the tuner next week. I am scared of doing that though as I dont want to suck anything down into the intake.
On a better note. The throttle response and higher rmp performance is great. At first I didnt notice any difference, but on my way home I hit it hard from 3k 1st through third gear and felt it. Cant wait to see what the tune does. Car also sounds different. I imagine that is due to the lack of AIR/EGR and more air flow. Definitely got louder.
06-24-2011, 09:34 AM
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Reused the gaskets. The gaskets were fine. I didnt need to shave the bottom because I used the coolant crossover. I would think if the intake was leaking there would be some bigger issue involved with the idle/overall running of the car. Also, wouldnt a vacuum leak cause the idle to be high all the time? We torqued all the manifold bolts in proper order and to the right specs so I dont think that is an issue, but I can check for leaks there.
Im really leaning towards the T/B or the TPS sensor. At least thats what I hope for. I dont want to have to pull the intake off again.
Im really leaning towards the T/B or the TPS sensor. At least thats what I hope for. I dont want to have to pull the intake off again.
06-24-2011, 10:01 AM
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The intake gaskets are crush gaskets so once you torque them down once they wont be the same.
I have an m6 and when I was moving and put the car in neutral it would idle at 1500 until I came to a complete stop and then it would drop back to 1000. Car ran great to put down 420 with the leak.
It might be your sensors though if you really think thats what it is.
A tip for pulling the intake off, pull the fuel rails off and take it out with out them on it. it will make the job only take 20.
I have an m6 and when I was moving and put the car in neutral it would idle at 1500 until I came to a complete stop and then it would drop back to 1000. Car ran great to put down 420 with the leak.
It might be your sensors though if you really think thats what it is.
A tip for pulling the intake off, pull the fuel rails off and take it out with out them on it. it will make the job only take 20.
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06-24-2011, 10:28 AM
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Crush gaskets? The manifold gaskets are rubber and pressed into the intake ports. I mean they very well could be leaking. Ill check tonight with some carb cleaner. lol Im going to kick myself in the rear if it is the gaskets, because I HATE taking that damn thing off.
On a side note. DO NOT EVER BUY EMISSION HEADERS!!! I hate them, they suck, and I have never been more pissed off at a bolt in my life
On a side note. DO NOT EVER BUY EMISSION HEADERS!!! I hate them, they suck, and I have never been more pissed off at a bolt in my life
06-24-2011, 11:55 AM
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I had the same issue with I got my TB P&P. the TB blade wasnt closing all the way...I actually still need to adjust it a little and do the TPS relearn again. But same exact thing with high idle until coming to a complete stop.
06-24-2011, 02:05 PM
#10
Reused the gaskets. The gaskets were fine. I didnt need to shave the bottom because I used the coolant crossover. I would think if the intake was leaking there would be some bigger issue involved with the idle/overall running of the car. Also, wouldnt a vacuum leak cause the idle to be high all the time? We torqued all the manifold bolts in proper order and to the right specs so I dont think that is an issue, but I can check for leaks there.
