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LS2 almost stall at start up

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Old 05-17-2012, 07:42 PM   #1
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Default LS2 almost stall at start up

I have a drop out LS2 from an 2005 GTO in my RX7 and I can't figure out why it almost stalls when I start it, then seems to recover fine with no input from me. Only code I am throwing is P0315 (crankshaft variation not learned) but from what I have read that shouldn't have any effect on the drivability of the car. after it recovers it seems to run perfectly so I can't figure out why it is behaving this way on startup. engine is bone stock with long tubes and an aluminum LS7 flywheel and clutch.

Attached is a link to a video, (I know its upside down and have no idea why image shack flipped it.)

http://img221.imageshack.us/img221/3...3373008430.mp4
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Old 05-17-2012, 08:17 PM   #2
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Slow reacting IAC valve.........maybe......

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1998 WS6 T/A, AES 390ci fully forged iron block, LS6 intake, LS1 heads, 239/235 .600/.600 114 lsa, 1 7/8" Grot LT's, 3" w/Magnaflow, 4L60E, Strange 12 bolt, Baer brakes, Hotchkis STB, UMI PH Bar, LCA's w/relocation brackets, SFC's, LG G2 Super Springs. Hals FR, Bilsteins RR, 275/315.

427ci stroker died at 173,000 miles...what a great engine that was, built by the late, great - Dave DiLuca...RIP...
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Old 05-18-2012, 07:41 AM   #3
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I thought the DBW motors don't have an IAC valve, I thought they just used the throttle plate.
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Old 05-18-2012, 11:51 AM   #4
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Quote:
Originally Posted by Mike_72 View Post
I thought the DBW motors don't have an IAC valve, I thought they just used the throttle plate.
Without an IAC valve.....the PCM can't adjust the idle quickly. You're probably starting the engine and then its struggling to stay alive for that brief period because all thats feeding the engine with air is the small hole in the TB blade, if it even has that hole in it.
The IAC acts very fast to feed the engine air and take it away when throttle is given.

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1998 WS6 T/A, AES 390ci fully forged iron block, LS6 intake, LS1 heads, 239/235 .600/.600 114 lsa, 1 7/8" Grot LT's, 3" w/Magnaflow, 4L60E, Strange 12 bolt, Baer brakes, Hotchkis STB, UMI PH Bar, LCA's w/relocation brackets, SFC's, LG G2 Super Springs. Hals FR, Bilsteins RR, 275/315.

427ci stroker died at 173,000 miles...what a great engine that was, built by the late, great - Dave DiLuca...RIP...
-Life may not be the party we hoped for, but while we're here we might as well DANCE.
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Old 05-21-2012, 09:22 AM   #5
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Everything I read seems to confirm that the LS2 uses the throttle plate for idle control and not an IACV
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Old 05-21-2012, 05:16 PM   #6
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What opens and closes the TB plate to control idle if the pedal is not being pushed?

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1998 WS6 T/A, AES 390ci fully forged iron block, LS6 intake, LS1 heads, 239/235 .600/.600 114 lsa, 1 7/8" Grot LT's, 3" w/Magnaflow, 4L60E, Strange 12 bolt, Baer brakes, Hotchkis STB, UMI PH Bar, LCA's w/relocation brackets, SFC's, LG G2 Super Springs. Hals FR, Bilsteins RR, 275/315.

427ci stroker died at 173,000 miles...what a great engine that was, built by the late, great - Dave DiLuca...RIP...
-Life may not be the party we hoped for, but while we're here we might as well DANCE.
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Old 05-22-2012, 07:32 PM   #7
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from what I understand the same motor that drives the plate with an input from the DBW pedal is also used to control the plate for idle purposes by taking outputs from various sensors
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Old 05-22-2012, 07:32 PM
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