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Port and Polish unnatural starts

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Old Mar 26, 2011 | 10:58 PM
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Default Port and Polish unnatural starts
So, I port and polished my TB and my ls6 intake. I am 100% sure the TB closes all the way, I was very carefull not too over port it. When I start the car the motor jumps to almost 2k rpm, it quickly lowers down to around 1100 and then not long after goes down to the idle at about 700-800. No running issues or check engine warning. Is this normal? Just wanted to be sure I havent knocked a vacuum line loose or somthing that could be causing the problem. Thanks guys!

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Old Mar 27, 2011 | 12:43 AM
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Silly question but,
Was the engine warm or cold start, weather?
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Old Mar 27, 2011 | 01:00 AM
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From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
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Originally Posted by Speedaemonc4
So, I port and polished my TB and my ls6 intake. I am 100% sure the TB closes all the way, I was very carefull not too over port it. When I start the car the motor jumps to almost 2k rpm, it quickly lowers down to around 1100 and then not long after goes down to the idle at about 700-800. No running issues or check engine warning. Is this normal? Just wanted to be sure I havent knocked a vacuum line loose or somthing that could be causing the problem. Thanks guys!

Under the stock or current PCM conditions, the PCM commands a scaled amount of air on start-up with the stock TB.

Now that you have changed the factors of that particular table in the PCM (Ported it)the command air needs to be REDUCED or adjusted in the PCM.

The smaller the TB entrance with the current settings asked for air to accomodate that size TB, but now it is larger and can give it air easier the command needs to be reduced Thus the high revs then comming back down when the PCM senses too much air!

The TB motor is set to be at a certain angle, so you did not do anything to mess it up or anything

You will need to have a tuner (that has Hp-Tuners etc) reduce the command air on start-up!

Thanks,Matt
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Old Mar 27, 2011 | 01:05 AM
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Perhaps try the "idle relearn" procedure first.
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Old Mar 27, 2011 | 11:04 AM
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Originally Posted by JuicedZ
Silly question but,
Was the engine warm or cold start, weather?
It was from cold start, it wont do it after Ive been driving, but if I dont drive the car for the day then the next day it does it again.
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Old Mar 27, 2011 | 11:05 AM
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Originally Posted by madmatt9471
Under the stock or current PCM conditions, the PCM commands a scaled amount of air on start-up with the stock TB.

Now that you have changed the factors of that particular table in the PCM (Ported it)the command air needs to be REDUCED or adjusted in the PCM.

The smaller the TB entrance with the current settings asked for air to accomodate that size TB, but now it is larger and can give it air easier the command needs to be reduced Thus the high revs then comming back down when the PCM senses too much air!

The TB motor is set to be at a certain angle, so you did not do anything to mess it up or anything

You will need to have a tuner (that has Hp-Tuners etc) reduce the command air on start-up!

Thanks,Matt
Thats kinda what I figured but I just wanted to get another opinion before I drove it again. Thanks guys, once I finish the rest of my setup Ill take it to get tuned.
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Old Mar 27, 2011 | 12:32 PM
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From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
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Originally Posted by MTPZ06
Perhaps try the "idle relearn" procedure first.
Unfortunetaly that wont work for a PP TB, it has to do with set tables in the PCM and the re-learn trick wont do it for such a drastic change

It does work great for CAI though

Thanks,Matt
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Old Mar 27, 2011 | 12:34 PM
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From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
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Originally Posted by Speedaemonc4
Thats kinda what I figured but I just wanted to get another opinion before I drove it again. Thanks guys, once I finish the rest of my setup Ill take it to get tuned.
You are right and that will be the best thing to do. It's not too bad to deal with for a while but if you want to show it to someone and fire it up - they think "what is wrong with it?"

Let me know how it goes when it is done - looking forward to the results

Thanks,Matt
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Old Mar 27, 2011 | 02:06 PM
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Originally Posted by Speedaemonc4
Thats kinda what I figured but I just wanted to get another opinion before I drove it again. Thanks guys, once I finish the rest of my setup Ill take it to get tuned.
Befoe yo do that,, check for vacum leaks and then ty the idle relearn procedre, I ported nmeros LS1/6 TB and never had an idle issue after it was reinstalled:

AUTOMATIC TRANS:
ign. off
remove pcm batt fuse
wait 5 min
replace pcm batt fuse
a/c off
park brake and block drive wheels(do not use brake)
start vehicle
allow coolant to reach over 176F
shift into drive
wait 5 mins
turn on a/c
wait 5 mins
shift to park
wait 5 mins
turn off a/c
wait 5 mins
turn off engine. off

MANUAL TRANS :

ign. off
remove pcm batt fuse
wait 5 min
replace pcm batt fuse
a/c off
park brake and block drive wheels(do not use brake) PUT VEHICLE IN NEUTRAL
start vehicle
allow coolant to reach over 176F
turn on a/c
wait 5 mins
turn off a/c
wait 5 mins
turn off engine for 30 secs
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Old Mar 27, 2011 | 02:10 PM
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Kinda what I was getting at...never hurts to try something for free.

Originally Posted by Bill Curlee
Befoe yo do that,, check for vacum leaks and then ty the idle relearn procedre, I ported nmeros LS1/6 TB and never had an idle issue after it was reinstalled:

AUTOMATIC TRANS:
ign. off
remove pcm batt fuse
wait 5 min
replace pcm batt fuse
a/c off
park brake and block drive wheels(do not use brake)
start vehicle
allow coolant to reach over 176F
shift into drive
wait 5 mins
turn on a/c
wait 5 mins
shift to park
wait 5 mins
turn off a/c
wait 5 mins
turn off engine. off

MANUAL TRANS :

ign. off
remove pcm batt fuse
wait 5 min
replace pcm batt fuse
a/c off
park brake and block drive wheels(do not use brake) PUT VEHICLE IN NEUTRAL
start vehicle
allow coolant to reach over 176F
turn on a/c
wait 5 mins
turn off a/c
wait 5 mins
turn off engine for 30 secs
Reply
0

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