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A bad Sunday

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Old Sep 17, 2017 | 04:00 PM
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Hi, very new to this gas stuff, and a little out of element. Only had diesel trucks, wanted to play in the gas world. I ended up buying a "turn key " toy. 2008 2500 Silverado, ly6 with a s475 turbo. Exhaust was a cab dump. I didn't like that. Disconnected the battery, changed the exhaust. Reconnected the batt, turned the key, truck fires, jumps to 2000 or so rpm, and dies. Stepping on the gas does nothing. Got out, fuel leaking on the ground through the exhaust. What did I mess up???
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Old Sep 17, 2017 | 08:42 PM
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What all did you take apart to redo the exhaust?
OR inadvertently tear loose while doing the above?
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Old Sep 17, 2017 | 09:08 PM
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Took off the exhaust clamp on the dump elbow and that's it.
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Old Sep 17, 2017 | 09:17 PM
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Something happened by disconnecting the battery. Why did you, unless you had to do some welding on the truck?
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Old Sep 17, 2017 | 09:39 PM
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Yep we did some welding . I mean a guy should be able to change a battery with his truck not starting again??
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Old Sep 17, 2017 | 10:35 PM
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You disconnected BOTH cables? SOMETHING got thrown off electrically somewhere.
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Old Sep 19, 2017 | 07:34 PM
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tig welding? the HF start will fry the pcm...or so ive been told. never tried it.
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Old Sep 19, 2017 | 07:36 PM
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Turned out to be the cleared codes were the issue.
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Old Sep 19, 2017 | 08:30 PM
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The cleared codes? No mention of this before....
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Old Sep 19, 2017 | 08:52 PM
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Disconnecting the battery cleared the active codes. Since my hp tuning is speed density, until the code goes for the mass air sensor being Mia the truck runs like **** . Soon as we got it trip the code boom back to normal.
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Old Sep 19, 2017 | 08:57 PM
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Ahhhhhhh! Gotcha....
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Old Sep 19, 2017 | 09:14 PM
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Oh man I used to go through that all the time. When you upload a tune it did the same thing.

WHen you first start, it checks and waits for the maf, sometimes it can take 3-5 seconds.
The fix ended up being set the maf table to an airflow which can idle the engine while it looks for the maf. Also I noted some of the factory tune tables have very low cranking pulse widths for the first 2 seconds, especially in cold cells, if I had to guess for oil priming perhaps. This can further delay cold start when the battery was disconnected and no maf is present.
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Old Sep 20, 2017 | 12:25 PM
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Originally Posted by kingtal0n
Oh man I used to go through that all the time. When you upload a tune it did the same thing.

WHen you first start, it checks and waits for the maf, sometimes it can take 3-5 seconds.
The fix ended up being set the maf table to an airflow which can idle the engine while it looks for the maf. Also I noted some of the factory tune tables have very low cranking pulse widths for the first 2 seconds, especially in cold cells, if I had to guess for oil priming perhaps. This can further delay cold start when the battery was disconnected and no maf is present.
You treed me. I was just about to post up - take every cell in your maf curve below 15 g/s and set them all to 15. You'll have fuel until you code out on a rewrite
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