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99 LS1 shutting off when warm/in traffic

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Old 03-20-2017, 10:00 PM   #1
nad
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Exclamation 99 LS1 shutting off when warm/in traffic

Having a problem with my 99 Camaro LS1, cam/ls6 intake. The car runs great, drives great otherwise. Back in July on a VERY HOT day I did a car cruise, and when idling in slow moving traffic, the car just shut off. Only way to get it to start was to turn the key all the way off, and it would start back up with NO ISSUE. But would only run maybe 5 minutes, whether I was moving or not. Only way I could get it home was to park it, shut it off, and leave it set for about an hour, then I could make the 15 minute drive home with no issues.

This past weekend I went to the local 1/4 mile track, and when waiting in the staging lanes, the car started to backfire really bad. I didn't think anything of it, because the weather was a cool 60*F. Suddenly the car just turned off. I tried cranking and it wouldn't start back up. Had to turn the key all the way back, and then the car started right up no issue. It died again about 4 times in the staging lanes. Finally, I got to the line to make a pass, and at about the 60' mark, I went to shift, and it just died. Coasted all the way down the track, trying to start it.

Once I got it parked, I turned the key all the way off, and then it fired back up enough to get it parked in the lot. I let it set about 2 hours, and drove it 60+ miles home without issue.

The issue seems to only show up when I'm driving in very slow traffic or just idling. The car does not overheat. Battery is brand new, like 3 weeks old. No check engine light, no codes stored. Absolutely no running issues at all with highway driving, or normal street driving. Checked the obvious grounds at the front of the motor.

Please help!!

Last edited by nad; 03-20-2017 at 10:24 PM.
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Old 03-21-2017, 04:04 PM   #2
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This is a complete longshot but my dad had a similar issue with an LT1 swapped Chevelle doing very similar things. When his PCM got hot it would do this. Pull your PCM and make sure you have no moisture in the connections but also see how it feels when your driving and it happens, see if it is getting hot. Again this is a long shot but if you have no codes could be your issue
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Old 03-22-2017, 10:21 PM   #3
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Thanks for the suggestion, I guess the only way to narrow it down would be to just start swapping parts until the problem goes away. Biggest problem is, I've had this car for a year and only had this happen 3 or 4 times. Only happens when the car is driven hard or idled in high heat situations for long periods of time.
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Old 03-23-2017, 08:41 AM   #4
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Just let us know your outcome on the fix for future purposes. I read so many threads that get me roped in and then no fix is ever posted lol
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Old 03-31-2017, 06:03 PM   #5
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Does the SES check engine light come on when this happens? Any codes?

My wife's Grand Am would randomly shut of like you describe no codes etc. It was a dirty fuel filter. The car would restart if it sat for a little while. Changed filter and it fixed issue.
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Old 03-31-2017, 07:03 PM   #6
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I just noticed you said Cam and ls6 intake.... what cam? Any other mods done to the car?
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Old 03-31-2017, 10:41 PM   #7
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Quote:
Originally Posted by N20zuki View Post
I just noticed you said Cam and ls6 intake.... what cam? Any other mods done to the car?
Tick Performance SNS Stage 2 (226/234 .605/.612 110 lsa), hardened pushrods, BTR dual springs, built 6 spd, 25% underdrive pulley, long tubes, true duals, QP 9" rear.

Also, I did some digging for stored codes, and came up with P1637 which is the Generator L Terminal code for the alternator. I inspected the excitor wire and connector and it seems to be okay, but I pulled the alternator and will have it tested tomorrow.

Is it at all possible that the alternator is causing this issue?

Also, I will replace my fuel filter ASAP also, couldn't hurt, who knows when the last time it's been replaced...

Last edited by nad; 03-31-2017 at 10:52 PM.
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Old 03-31-2017, 10:42 PM   #8
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Heat sensitive ignition module...
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Old 03-31-2017, 11:03 PM   #9
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Heat sensitive ignition module...
Okay, I've seen a lot of things about that, but with this being an LS car, where is the ignition module located? All the stuff I've read about ignition module issues pertain to LT1 cars.
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Old 04-01-2017, 02:31 PM   #10
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Check in the fuse box.
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Old 04-01-2017, 02:37 PM   #11
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Thanks, that really narrows it down for me, appreciate the advice. 🙄
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Old 04-04-2017, 09:32 PM   #12
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Nad, how is the car doing?
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Old 04-04-2017, 09:43 PM   #13
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Haven't done much with it, other than chasing issues. Haven't driven it enough to replicate the problem. It's throwing a p1637 code, generator L circuit or whatever. I've had the alternator "tested" at 3 parts stores, and it passes. But it still throws the code. I'm doubting that this is what's causing my issues, but I just want to get the car to run without throwing any codes to eliminate all possibilities.
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Old 04-07-2017, 01:02 PM   #14
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Any TPS throttle position sensor codes?

A friend's truck did something similar and it was a bad TPS. Only did it when the car got fully warmed up and hot.

Let us know what you find and best wishes.
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Old 04-09-2017, 09:22 PM   #15
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Originally Posted by 99 Black Bird T/A View Post
Any TPS throttle position sensor codes?

A friend's truck did something similar and it was a bad TPS. Only did it when the car got fully warmed up and hot.

Let us know what you find and best wishes.
No TPS codes, but I haven't driven the car since I've started digging into this alternator issue. At this point I'm willing to replace any/all cheap electronic parts just to rule them out as the culprit. I'll keep you updated, once I get this alternator replaced and drive the car a bit, I'll see if I come up with any new codes.
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