LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Rough idle when cold, help!

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Old Jul 22, 2009 | 04:18 PM
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Default Rough idle when cold, help!

Hey guys, lately i've noticed that when I start my car up cold it will idle down low and start to idle a little rough like it has a cam then it will jump up to regular idle and keep doing that until it warms up a little. Also if i get in and drive it while its doing this it kind of cuts out on when im driving noramlly. If i rev it up its fine and when it warms up its fine and runs great. Anyone have any ideas of what it could be? Bad o2's? Dirty sensor somewhere?
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Old Jul 22, 2009 | 04:26 PM
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Originally Posted by 93BlackZ28
Hey guys, lately i've noticed that when I start my car up cold it will idle down low and start to idle a little rough like it has a cam then it will jump up to regular idle and keep doing that until it warms up a little. Also if i get in and drive it while its doing this it kind of cuts out on when im driving noramlly. If i rev it up its fine and when it warms up its fine and runs great. Anyone have any ideas of what it could be? Bad o2's? Dirty sensor somewhere?
Well after first start when the car is cold it is in open loop and it isn't using the o2 sensors yet. Once it warms up and switches to closed loop it utilizes the o2 sensors and MAF. You might have a problem that the o2's are compensating for when in closed loop...making it run better. Any codes?
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Old Jul 22, 2009 | 04:30 PM
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Well the SES light has been on since I did the headers so I don't know if it has thrown any other codes. I've looked before and I think it threw some kind of o2 sensor code though. I'll have to check.
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Old Jul 22, 2009 | 04:32 PM
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Originally Posted by 93BlackZ28
Well the SES light has been on since I did the headers so I don't know if it has thrown any other codes. I've looked before and I think it threw some kind of o2 sensor code though. I'll have to check.
Yeah, scan it and post the codes.
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Old Jul 23, 2009 | 12:00 AM
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Originally Posted by ss.slp.ls1
Yeah, scan it and post the codes.
possibly TPS sensor? I agree scan it and post codes, then go from there. Could be the TPS, and numerous sensors.

Devin
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Old Jul 23, 2009 | 10:02 PM
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P0140- No activity in o2 sensor Bank 1 Sensor 2
P0135- Heat circut malfunction Bank 1 Sensor 1
P0160- Circut No activity Bank 2 Sensor 2
P0400- EGR
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Old Jul 23, 2009 | 11:18 PM
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i would replace that o2 sensor, the heater malfunction referes to the 02 sensor. I would get the EGR all tuned out by DYNO DAN asap.

http://www.obd-codes.com/p0135
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Old Jul 23, 2009 | 11:20 PM
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Originally Posted by 93BlackZ28
P0140- No activity in o2 sensor Bank 1 Sensor 2
P0135- Heat circut malfunction Bank 1 Sensor 1
P0160- Circut No activity Bank 2 Sensor 2
P0400- EGR
this will help with all your codes, hopes this helps.

http://www.performanceworks1.com/PDF...eters%20V8.pdf
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Old Jul 24, 2009 | 12:14 AM
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Thanks
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Old Jul 24, 2009 | 12:16 AM
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Someone who knows about this stuff please help! What should I do?
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Old Jul 24, 2009 | 12:18 AM
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well sounds like the opposite of a typical o2 problem.

you removed the EGR on the car I'm assuming since you're running an ORY?
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Old Jul 24, 2009 | 12:21 AM
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also did you make your own O2 extensions or buy them?
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Old Jul 24, 2009 | 08:13 AM
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The EGR has been removed and yes I ghettoed my own o2 extensions
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Old Jul 24, 2009 | 09:23 AM
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How did you wire them..maybe you have a wire crossed. Are the back ones completely gone..the ones that would be behind the Cats if they were still there?
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Old Jul 24, 2009 | 12:13 PM
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Check the wires and connections to your drivers side front o2 sensor. If it all checks out, I would pick up a new pair of sensors and a pair of o2 extenstions.

The other codes, don't worry about them. You can tune them out later.
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Old Jul 24, 2009 | 12:49 PM
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They were wired correctly and there is no rear o2 on this car, just the front 2 in the headers.

I'll check out the wires. Last time I was under my car i noticed that the plastic wire loom I wrapped my o2 extensions in was completely melted and the wires were exposed so thats probably whats going on. Thanks for your help. I'll check it out and post up.
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Old Jul 24, 2009 | 01:49 PM
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Yea maybe one crossed.
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Old Jul 24, 2009 | 01:58 PM
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Originally Posted by the_merv
Yea maybe one crossed.
i thought my fault code list helped quite well haha, I was thinking that he crossed a wire/02 sensor was reading bad.
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