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Old 03-09-2011, 10:19 AM
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Default ls1 running terrible

Hello all. Recently, my 3rd gear starting going out in my transmission. I knew it was inevitable to need to yank it, which I plan on doing, but figured I'd change out the fluid just in case. Car is running fine. I take it out back, prop it up, change out the fluid, finish my business, put the car back on the ground, go to test drive it, and the car is running like absolute dogpiss. At idle, it is very rough, very very rich (richer than usual, usually it is pretty rich at idle, but the FI adjusts and takes fuel out after about 10 seconds or so), and it does not go away until about 15-20 mins of regular driving.

It has a cam (234/240 @.05), intake, headers and a Borla catback exhaust on it, but it was running JUST fine before I changed the fluid in the t56. There are no 02 sims after the cats, and I know I need them, but they are not there.

I am at a loss. I am not into this FI electronic bullshit. Did I rub an o2 sensor the wrong way? What can cause the FI to take so long to take enough fuel out?
Old 03-09-2011, 10:39 AM
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How do you know it is taking 10+ seconds to adjust the fuel? What software/monitor are you using to watch the fuel trims? What wideband are you using to monitor the Air/Fuel ratio? What A/F ratio are you seeing at idle?
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Old 03-09-2011, 10:44 AM
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Originally Posted by Matt@Texas-Speed
How do you know it is taking 10+ seconds to adjust the fuel? What software/monitor are you using to watch the fuel trims? What wideband are you using to monitor the Air/Fuel ratio? What A/F ratio are you seeing at idle?
No widebands, just watching the idle and gauging how rough it is running/car shaking. I don't have any software. It is popping through the exhaust sitting at idle, when it decelerates...it is very strange. Let's say I'm going down the road around 45mph, I let out the clutch, the car will A) for around the first 10 mins of driving, it will nearly die, idle down to around 500 RPM, just keep around there, and after about 10-20 mins of driving, B) once I let the clutch out going 45mph, it will idle ridiculously high, around 1500 - 2000 RPM's. It's ******* insane, and pissing me off. It will NOT idle back down unless I am sitting at a dead stop, and even then, it is not completely right.

I hope this makes some kind of sense.
Old 03-09-2011, 10:54 AM
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Any chance you pinched or otherwise damaged the wires going to the O2 sensors (or any other wires) when re-installing the tranny?
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Old 03-09-2011, 10:57 AM
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Originally Posted by Matt@Texas-Speed
Any chance you pinched or otherwise damaged the wires going to the O2 sensors (or any other wires) when re-installing the tranny?
I haven't take it out yet, just changed the fluid out in it. There is only one o2 sensor, and it's in the passenger side collector. Would it throw any codes on an OBDII scan?
Old 03-09-2011, 11:01 AM
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It's neither here nor there, but you really should have two O2 sensors up front in the end of the headers (collector). I'd suggest getting a friend or shop with HPtuners or similar to log it and see what's going on. It is very strange that is started doing this with no other changes aside from the fluid!
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Old 03-09-2011, 11:10 AM
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Originally Posted by Matt@Texas-Speed
It's neither here nor there, but you really should have two O2 sensors up front in the end of the headers (collector). I'd suggest getting a friend or shop with HPtuners or similar to log it and see what's going on. It is very strange that is started doing this with no other changes aside from the fluid!
Ah, yes. I do have two up front, and one at the end of the passenger collector. Should I have another in the drivers side collector as well?
Old 03-09-2011, 11:15 AM
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Location of the front sensors will change depending on what headers you run, custom exhaust work, etc....but yes, the PCM "watches" 2 O2 sensors on the front channel. The rear sensors don't have any affect on A/F ratio, but rather just monitor catalytic converter performance. Even when you delete them completely without tuning, only an SES light is thrown, but that has NO effect on A/F.
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Old 03-09-2011, 11:23 AM
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Originally Posted by Matt@Texas-Speed
Location of the front sensors will change depending on what headers you run, custom exhaust work, etc....but yes, the PCM "watches" 2 O2 sensors on the front channel. The rear sensors don't have any affect on A/F ratio, but rather just monitor catalytic converter performance. Even when you delete them completely without tuning, only an SES light is thrown, but that has NO effect on A/F.
So, the o2 sensor at the collector does not affect A/F readings? I know the ones after the cats just tell if the cats are working or not, but the one at the passenger collector, what's that one for?

Thanks for your help.
Old 03-09-2011, 11:37 AM
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The front sensors do control the A/F ratio. The rear ones do not. Sorry if I was not clear on that
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Old 03-09-2011, 12:20 PM
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Hmm, funny issue here. I dont have much advice.

You sure you didnt overfill it? Maybe the new fluid caused a part in the trans to act up. Do you have a stall?
Old 03-09-2011, 12:24 PM
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Originally Posted by 180ls1
Hmm, funny issue here. I dont have much advice.

You sure you didnt overfill it? Maybe the new fluid caused a part in the trans to act up. Do you have a stall?
Negative. This is a 6 speed.

The only thing I can think of with regard to the transmission/fluid is the speed reluctor/sensor? Could overfilling it cause it to act up? I put about 3.75 in there, not even 4 full quarts.
Old 03-09-2011, 02:44 PM
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Im pretty sure over filling the tranny has nothing to do with how the motor runs. A vacumn leak could explain the high idle. The low idle sounds like a miss if the motor its shaking. Is there any lights on?
Old 03-09-2011, 03:03 PM
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Originally Posted by parks450
Im pretty sure over filling the tranny has nothing to do with how the motor runs. A vacumn leak could explain the high idle. The low idle sounds like a miss if the motor its shaking. Is there any lights on?
SES light is on, but I'm almost 100% positive it is because the rear O2's aren't plugged in. I am stumped. I'm going to unplug the battery tonight and clear anything that may have happened since.
Old 03-09-2011, 03:22 PM
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I am almost positive that you may have pinched some o2 wires.
Old 03-09-2011, 03:30 PM
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Originally Posted by Greekey
I am almost positive that you may have pinched some o2 wires.
The one that goes in my passenger collector? I thought that O2 sensor had nothing to do with A/F. The front ones aren't anywhere near where I was working.
Old 03-09-2011, 11:17 PM
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So, did a bunch of things tonight. First, I went and got an OBDII scan. Error codes P0102, P0135 and P0155 showed up. P0102 is unexpected, the other two are the rear cat o2's, and is expected. The first one, P0102, says: 'MAF or VAF A circuit low input'. Could that be causing all my problems? Does that mean I need a new MAF sensor?

I also cleared out all codes from the PCM. After I did that, I turned on the car, it ran rich as ****, proceeded to make fireworks out the exhaust at regular intervals, but leaned up over a period of about 5 minutes, with no more popping out of the exhaust. I also took out my air filter, decided to clean it. It is a K&N come to find out, and they sell a cleaning kit for it. That is cleaning right now.

..any ideas?

EDIT: also, I was wrong earlier: there are two o2 sensors in the collectors, one on the passenger side and another on the drivers side. so, that makes 4 plugged in, and 2 missing (cat o2's).

Last edited by mrdreex; 03-09-2011 at 11:25 PM.
Old 03-09-2011, 11:26 PM
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Personally if your getting that code. I would spray the MAF with maf cleaner, the oil on filters can cause problems with the MAF. Also i would pop off the throttle body and clean the sensors associated with that. Should be a 20-30min process or so.
Old 03-09-2011, 11:33 PM
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Originally Posted by 180ls1
Personally if your getting that code. I would spray the MAF with maf cleaner, the oil on filters can cause problems with the MAF. Also i would pop off the throttle body and clean the sensors associated with that. Should be a 20-30min process or so.
I did take out the MAF, sprayed it with some carburetor cleaner, let it dry, put it back in, and still nothing changed. I also unhooked the wiring harness from it while the car was running, and the cars idle didn't change a single bit, or throttle response, mixture, etc.
Old 03-10-2011, 12:47 AM
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I just got done drying/oiling my filter, put it back in, turned the car on, and not 2 seconds after it started up and ran, the SES light came back on after resetting the codes earlier tonight...WTFFFFFFFFFFFFF...the car has ran a grand total less than 10 mins, probably a 1/4 mile distance driven..wtf gives!




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