1993 LT1 Idle surging
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On The Tree
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I think the problem lies somewhere with the work you did on it during the tune up.
Are you 100% certain that the opti is indexed correctly? If I'm not mistaken, you have a spline drive and those are easy to get wrong.
Do you still have the old components you took off the car when putting the new stuff on it?
Are you 100% certain that the opti is indexed correctly? If I'm not mistaken, you have a spline drive and those are easy to get wrong.
Do you still have the old components you took off the car when putting the new stuff on it?
I'll unplug the O2's and run another log, I'll reset the fuel trims right when the log will start.
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On The Tree
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Did another data log, this time once the engine went into closed loop, I jumped under it, unplugged both O2's and reset the fuel trims. Smoothed out a bit, but still idling with a hiccup. Thoughts on this one? Fuel trims did stay equal after the O2's were unplugged.
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Did another data log, this time once the engine went into closed loop, I jumped under it, unplugged both O2's and reset the fuel trims. Smoothed out a bit, but still idling with a hiccup. Thoughts on this one? Fuel trims did stay equal after the O2's were unplugged.
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From: Maricopa, AZ
Looked over the log. Something is causing the O2's to fluctuate (ever so slightly) even though they are disconnected. That shouldn't happen. I wonder if maybe you have a loose ground for the PCM?
The BLMs did reset to 128 though and the idle showed smooth and steady. I'm not sure what you mean by hiccup. Can you elaborate? Maybe post a video?
The BLMs did reset to 128 though and the idle showed smooth and steady. I'm not sure what you mean by hiccup. Can you elaborate? Maybe post a video?
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On The Tree
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Ran another log with the O2's disconnected the entire time. Fuel trims stayed at 128, but the idle was still fluctuating, when warmed up it smoothed out better, but still somewhat sputtering out the left tail pipe (the hiccup I mentioned). Is it strange that the engine didn't throw any codes, no CEL. I noticed power to the O2 wires as well, not much, but .453 something near there. Check out the log.
Thread Starter
On The Tree
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Ran another log with the O2's disconnected the entire time. Fuel trims stayed at 128, but the idle was still fluctuating, when warmed up it smoothed out better, but still somewhat sputtering out the left tail pipe (the hiccup I mentioned). Is it strange that the engine didn't throw any codes, no CEL. I noticed power to the O2 wires as well, not much, but .453 something near there. Check out the log.
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Nominal voltage for the O2's is 450mV. With them disconnected, you should see .450v on both O2's in the datalog with zero fluctuations. They are fluctuating, so something is wrong. Bad connection or ground from the O2 maybe, not sure. But, that can cause issues.
The sputtering is unreleated. And it seems the IAC adjustments are too.... ish. The fluctuations did get better, but they are still there. At 330 seconds you have a logged RPM jump to 3437 with no throttle input (not possible) for less than a 10th of a second (also not possible). After that, the rpm fluctuates a little more aggressively a couple times, then the idle get's very smooth. I would have to assume that there is a heat soak issue that improves something on the engine. Usually a gasket in that case. Since the O2's have no influence, it would have to be on the intake side of things.
Do you still have the EGR? I don't remember if you said you did or not. A signature of your vehicle and mods would help us with helping you.
Also, just wondering, are you at a high elevation? You can google search your location and elevation to find out what it is if you don't know it. 90.8kPa (the baro in your log) and 55°F points to at least 3000 ft. I've always gotten Baro's higher than that when at 3K feet elevation and higher temps, so I'd lean to you being at that elevation or higher. If you aren't, the MAP is reading low (this will make the engine fuel lean - actual- and the O2's will tell it to add fuel). That's the reason I ask.
A video of the sputtering would be nice if you could post one.
The sputtering is unreleated. And it seems the IAC adjustments are too.... ish. The fluctuations did get better, but they are still there. At 330 seconds you have a logged RPM jump to 3437 with no throttle input (not possible) for less than a 10th of a second (also not possible). After that, the rpm fluctuates a little more aggressively a couple times, then the idle get's very smooth. I would have to assume that there is a heat soak issue that improves something on the engine. Usually a gasket in that case. Since the O2's have no influence, it would have to be on the intake side of things.
Do you still have the EGR? I don't remember if you said you did or not. A signature of your vehicle and mods would help us with helping you.
Also, just wondering, are you at a high elevation? You can google search your location and elevation to find out what it is if you don't know it. 90.8kPa (the baro in your log) and 55°F points to at least 3000 ft. I've always gotten Baro's higher than that when at 3K feet elevation and higher temps, so I'd lean to you being at that elevation or higher. If you aren't, the MAP is reading low (this will make the engine fuel lean - actual- and the O2's will tell it to add fuel). That's the reason I ask.
A video of the sputtering would be nice if you could post one.
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On The Tree
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Nominal voltage for the O2's is 450mV. With them disconnected, you should see .450v on both O2's in the datalog with zero fluctuations. They are fluctuating, so something is wrong. Bad connection or ground from the O2 maybe, not sure. But, that can cause issues.
Elevation here is 3330ft. You nailed it. As for the O2 ground, I traced the wire, and about 16" from the connector to the O2, there is another wire spliced into the O2 wire, is this the ground? Where are they grounded, by the coil possibly? Do you think a new MAP sensor might be a good idea? It's about the only sensor I haven't replaced.
The sputtering is unreleated. And it seems the IAC adjustments are too.... ish. The fluctuations did get better, but they are still there. At 330 seconds you have a logged RPM jump to 3437 with no throttle input (not possible) for less than a 10th of a second (also not possible). After that, the rpm fluctuates a little more aggressively a couple times, then the idle get's very smooth. I would have to assume that there is a heat soak issue that improves something on the engine. Usually a gasket in that case. Since the O2's have no influence, it would have to be on the intake side of things.
Do you still have the EGR? I don't remember if you said you did or not. A signature of your vehicle and mods would help us with helping you.
Also, just wondering, are you at a high elevation? You can google search your location and elevation to find out what it is if you don't know it. 90.8kPa (the baro in your log) and 55°F points to at least 3000 ft. I've always gotten Baro's higher than that when at 3K feet elevation and higher temps, so I'd lean to you being at that elevation or higher. If you aren't, the MAP is reading low (this will make the engine fuel lean - actual- and the O2's will tell it to add fuel). That's the reason I ask.
A video of the sputtering would be nice if you could post one.
Elevation here is 3330ft. You nailed it. As for the O2 ground, I traced the wire, and about 16" from the connector to the O2, there is another wire spliced into the O2 wire, is this the ground? Where are they grounded, by the coil possibly? Do you think a new MAP sensor might be a good idea? It's about the only sensor I haven't replaced.
The sputtering is unreleated. And it seems the IAC adjustments are too.... ish. The fluctuations did get better, but they are still there. At 330 seconds you have a logged RPM jump to 3437 with no throttle input (not possible) for less than a 10th of a second (also not possible). After that, the rpm fluctuates a little more aggressively a couple times, then the idle get's very smooth. I would have to assume that there is a heat soak issue that improves something on the engine. Usually a gasket in that case. Since the O2's have no influence, it would have to be on the intake side of things.
Do you still have the EGR? I don't remember if you said you did or not. A signature of your vehicle and mods would help us with helping you.
Also, just wondering, are you at a high elevation? You can google search your location and elevation to find out what it is if you don't know it. 90.8kPa (the baro in your log) and 55°F points to at least 3000 ft. I've always gotten Baro's higher than that when at 3K feet elevation and higher temps, so I'd lean to you being at that elevation or higher. If you aren't, the MAP is reading low (this will make the engine fuel lean - actual- and the O2's will tell it to add fuel). That's the reason I ask.
A video of the sputtering would be nice if you could post one.
Thread Starter
On The Tree
Joined: Feb 2011
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vation here is 3330ft. You nailed it. As for the O2 ground, I traced the wire, and about 16" from the connector to the O2, there is another wire spliced into the O2 wire, is this the ground? Where are they grounded, by the coil possibly? Do you think a new MAP sensor might be a good idea? It's about the only sensor I haven't replaced
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From: Maricopa, AZ
No need to replace the MAP, at your elevation with it's readings you are good to go on that.
The O2's should have 2 wires each IIRC for the 1993 LT1, one signal and one ground, I'll have to double check this though. Many go with 4 Wire preheated O2's. It's a simple upgrade that adds 2 wires for the heater in the O2, one is ground the other is 12V ignition power.
The O2's should have 2 wires each IIRC for the 1993 LT1, one signal and one ground, I'll have to double check this though. Many go with 4 Wire preheated O2's. It's a simple upgrade that adds 2 wires for the heater in the O2, one is ground the other is 12V ignition power.
Thread Starter
On The Tree
Joined: Feb 2011
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No need to replace the MAP, at your elevation with it's readings you are good to go on that.
The O2's should have 2 wires each IIRC for the 1993 LT1, one signal and one ground, I'll have to double check this though. Many go with 4 Wire preheated O2's. It's a simple upgrade that adds 2 wires for the heater in the O2, one is ground the other is 12V ignition power.
The O2's should have 2 wires each IIRC for the 1993 LT1, one signal and one ground, I'll have to double check this though. Many go with 4 Wire preheated O2's. It's a simple upgrade that adds 2 wires for the heater in the O2, one is ground the other is 12V ignition power.
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On The Tree
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It's seeming to me that I'm getting no where. The computer seems to be the issue to me. I'd of thought that the work I did on it had something to do with it, but I've went over everything 2 and 3 times and the issue stays. What's the deal with it not tripping the SEL with the O2'same unplugged? This issue is getting so old and disappoints me with every minute I work on it. Thoughts on trying to track down a new computer? Would I need the entire assembly, or just the small blue chip?
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On The Tree
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Thread Starter
On The Tree
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Update, I just replaced every ground on the engine, and messed a bit more with the msd opti timing screw (2 turns out), the surging has seemed to subsided. But the driverside exhaust is still making a (puff puff puff) sound, while the other side is steady. One side O2 is showing very, very little voltage...like 0.004 volts steady, they are both plugged in and the fuel trims haven't changed. Just ran it up till the fans kicked on and though it's not perfect, the idle is staying relatively steady. Also noticed it wasnt showing as going into closed loop. I'll check out the O2 connector after it cools down a bit.
I can't figure out how to post a picture of the exhaust "puffing"
I can't figure out how to post a picture of the exhaust "puffing"
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From: Maricopa, AZ
Low O2 voltage means lean, .004 means really lean. No signal at all should read .450. I'm going to assume that the O2 reading the .004V is on the side that's puffing? Is that a good assumption?
The puff puff puff sound, is it accompanied by smoke?
Also, what is your exhaust set up? Is it true duals with no balancing pipe (x or H pipe)? Long tubes or stock manifolds?
The puff puff puff sound, is it accompanied by smoke?
Also, what is your exhaust set up? Is it true duals with no balancing pipe (x or H pipe)? Long tubes or stock manifolds?
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From: Maricopa, AZ
Skip to 2 minutes in this video. If you listen closely to the Camaro, you'll hear a little miss/puff/whatever sound. It's consistent. That sound was caused by an arcing spark plug wire on the #5 cylinder that touched the exhaust manifold and melted. I replaced that wire and all was good. It ran A LOT better afterwords too.