LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

How can I force open loop

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Old 10-13-2004, 08:46 AM
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How can I force open loop

How can I force my Z to stay in open loop? I'm trying something with emissions. Thanks.....
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Old 10-13-2004, 09:07 AM
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Re: How can I force open loop

Pull the AIR fuse and set an SES light? I think with SES light it stays in open loop and the fans turn on.

EDIT:
Cant pass inspection with SES light on, atleast in NJ, so that might defeat the purpose...duh stoopid me
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Old 10-13-2004, 09:17 AM
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Re: How can I force open loop

Ha thanks but I should have stated (and not with an SES light). Yep emissions inspectors don't like SES lights on. But thanks anyway.
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Old 10-13-2004, 09:30 AM
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Re: How can I force open loop

The easiest way to stay in open loop would be to unplug your O2 sensors, but that would set the SES light. Not sure what you are trying to do, since your car makes the least emmissions in closed loop, after everything is warmed up.
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Old 10-13-2004, 10:14 AM
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Re: How can I force open loop

Yes like ya said that would have the SES light on also. I just need a way to (temporarily), just long enough to get the emission test done, to stay in open loop. I'm going to try and run a fuel mixture to lower my CO's just during the test and 10 min. later change back. The tester is working with me a little. I might even get the tester to run the test while engine is cold, which would do it, but would like to keep him out of the loop as much as possible. Don't even want to go near the $50/$100 under the table thing. I'm also thinking of unplugging an injector while in open loop. Just a thought.
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Old 10-13-2004, 01:09 PM
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Re: How can I force open loop

Go into your constant tables in tunercats. Set minimum coolant temperature really high in order to enable closed loop. No codes.
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Old 10-13-2004, 01:23 PM
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Re: How can I force open loop

Originally Posted by PatriotTA
The easiest way to stay in open loop would be to unplug your O2 sensors, but that would set the SES light. Not sure what you are trying to do, since your car makes the least emmissions in closed loop, after everything is warmed up.
We did this on our 93 and it never threw a light.
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Old 10-13-2004, 01:29 PM
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Re: How can I force open loop

Originally Posted by atljar
Go into your constant tables in tunercats. Set minimum coolant temperature really high in order to enable closed loop. No codes.
Now that don't sound like something that I'm going to do with a screw driver/hammer.. LOL .. All I've got is an Autoxray for sensor/computer display, nothing to change stuff with. Is there nothing I can do (unplug/jumper), to force it?
Thanks alot for the help! I'm going to try and get this done this evening.....
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Old 10-13-2004, 02:07 PM
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Re: How can I force open loop

do everything that everyone said to get it into open loop, then take out the SES light bulb. Voila, no SES and in open loop, all with nothing but hand tools.
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Old 10-13-2004, 02:26 PM
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Re: How can I force open loop

Originally Posted by WhiteSSP
do everything that everyone said to get it into open loop, then take out the SES light bulb. Voila, no SES and in open loop, all with nothing but hand tools.
But as you are well aware I'm sure, the tester execpts a light when the key is turned to just the on position.

WS SICK -- I'll try the unplugged O2 when I get home.

Sure hope it works, THANKS for all the help!
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Old 10-13-2004, 02:38 PM
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Re: How can I force open loop

couldn't you unplug the coolant sensor from the water pump and plug it up?

that way the sensor never sees about 145* or whatever our cars go into closed loop at.

the thermostat would still work, and i don't know which sensor controls the fans, the one in the water pump or the one in the head, but if it's the one in the water pump, just make a jumper wire going to the white(power) wire of the fans, to a 12v source. then the fan will be on all the time, so you don't have to worry about overheating.
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Old 10-13-2004, 02:59 PM
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Re: How can I force open loop

Originally Posted by david97gsxr
couldn't you unplug the coolant sensor from the water pump and plug it up?

that way the sensor never sees about 145* or whatever our cars go into closed loop at.

the thermostat would still work, and i don't know which sensor controls the fans, the one in the water pump or the one in the head, but if it's the one in the water pump, just make a jumper wire going to the white(power) wire of the fans, to a 12v source. then the fan will be on all the time, so you don't have to worry about overheating.
I already have a switch for my fans but if I just pull the temp connector and eather jumper or leave it open, do you know if the will through a code or SES light. Thanks..
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Old 10-13-2004, 07:20 PM
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Re: How can I force open loop

Originally Posted by 93 RED Z
But as you are well aware I'm sure, the tester execpts a light when the key is turned to just the on position.

WS SICK -- I'll try the unplugged O2 when I get home.

Sure hope it works, THANKS for all the help!
Ah, didnt know that. We dont have emissions here (thank god), so i was just making a guess. Well best of luck to you.
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Old 10-13-2004, 07:26 PM
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Re: How can I force open loop

Originally Posted by 93 RED Z
I already have a switch for my fans but if I just pull the temp connector and eather jumper or leave it open, do you know if the will through a code or SES light. Thanks..

i wouldn't think it would if you just pull the sensor out of the the water pump. it's not like it has to be emerged in coolant. if you unplug the wires, or disconnect the sensor terminals/connector, it WILL throw a code. it needs to have a closed circuit or it will throw a code.

so, you'd need to pull the entire sensor out. and plug the hole with a pipe plug.

the only issue would be, you'd have to keep the sensor away from heat, if you just leave it dangling and under your hood temps reach 145, it will go into closed loop.

Last edited by david97gsxr; 10-13-2004 at 07:28 PM.
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Old 10-13-2004, 07:32 PM
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Re: How can I force open loop

also, if you have a DVOM, you could find out what the resistance is of the sensor when you first start the car. and then solder in some resistors to make it read that resistance when the car is warmed up....

if you wanted to go that route.
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