LS1 only runs for 3-5 seconds??

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Jul 11, 2003 | 06:15 AM

93LS1RX7

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From: Maryland

LS1 only runs for 3-5 seconds??

Well she is running now and open manifolds sound really really mean. I am having a little problem though that hopefully someone can help me with. When she starts she is a little hard to start sometimes and then once running only runs for about 3-5 seconds. I dont have any of the O2 sensors plugged in or the intake air temperature plugged in. So could the senors be the problem or what else could it be?? The check engine never goes off and if I manually hit the throttle body it dies almost right away the fuel pressure is reading 57-58 psi so i think the fuel is ok.

Any ideas or help would be greatly appreciated. BTW I dont have LS1 edit or Autotap to find out what the trouble codes or readings could be. I know I know I have just not gotten around to ordering it yet.

Oh yeah I didnt change the plugs that were in the car when I put it in. I pulled a few and they looked ok so I kept them. The motor only has about 15000 miles on it.

Thanks
Mike

I am guessing it is the VATS system. Can I disable it without LS1edit? SPEARTECH did my harness. Help guys.

Jul 11, 2003 | 08:45 AM

60Chevy

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Re: LS1 only runs for 3-5 seconds??

Without the O2 plugged in, it is forced open loop. Being open loop, the air mass calculation is very critical to keep it running. To calculate the air mass into the motor, it needs the air meter, air temp sensor, and manifold pressure sensor (3 pin in back of the intake). Even if you plug the air temp sensor in and let it hang in the engine bay, it is better then nothing. The advanced diagnostics see the temp sensor as a open. Both the absence of o2 sensors and no air temp sensor tells the computer it is a critical failure mode. VATS would not allow the fuel pump to turn on. So if you keep pressure during run, VATS is not an issue.

A cheap code reading tool can be bought from JC Whitney or Autozone for less than $200 and it will work on every OBD2 vehicle.

Jul 11, 2003 | 09:01 AM

93LS1RX7

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From: Maryland

Re: LS1 only runs for 3-5 seconds??

VATS actually just disables the injectors through the PCM. I found that out while researching my problem.

Jul 11, 2003 | 10:00 AM

Speartech

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From: Anderson, Indiana

Re: LS1 only runs for 3-5 seconds??

That is probably VATS, especially if the PCM hasn't been reprogrammed!
You can add a VATS module to get you up and running, but I would suggest a re-programming at some point, to get rid of all of the unused stuff that will keep your check engine light on all of the time.

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Jul 11, 2003 | 11:02 AM

68LSS1

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From: Tampa, Florida

Re: LS1 only runs for 3-5 seconds??

Listen to John, it's the VATS.

Jul 11, 2003 | 12:59 PM

Pro Stock John

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Re: LS1 only runs for 3-5 seconds??

I have seen a car with an unplugged IAT run like total crap and rev up really badly and the car would barely run. At least put a resistor in it.

Jul 11, 2003 | 01:45 PM

Briguy280Z

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From: Salinas

Re: LS1 only runs for 3-5 seconds??

I also believe it is the vats system. There is a circuit that you can build that will satisfy the PCM and keep the car running. The pcm requires a 50% duty cycle 30-60hz. Check out this link it will allow you to build one. I built one for my conversion and worked good.

http://www.fieroaddiction.com/passkey.html

I still had problems afterwards. If the engine PCM is programmed with Traction Control you will have to apply a 12V to the Engine Retard wire. I dont remember what color but i will look and repost.

Good Luck