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Discussion Starter · #1 ·
Just wondering which fuse controls the O2 sensor on a 92 LT1, and will the car run if this fuse is removed, and/or, if it will run, will it cause any harm to the engine?

That's it. Thanks.
 

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not 100 but.... if you remove the fuse it will be inoperable. you can damage cats after. its odb1 so check engine light most likely wont come on after you do this. i have a feeling the ECU though will run the car but fuel to air ratio wont be in parameters hence damaging the cat. is there a cheater box for this? just curios of why you are wanting to do this?
 

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Discussion Starter · #3 ·
not 100 but.... if you remove the fuse it will be inoperable. you can damage cats after. its odb1 so check engine light most likely wont come on after you do this. i have a feeling the ECU though will run the car but fuel to air ratio wont be in parameters hence damaging the cat. is there a cheater box for this? just curios of why you are wanting to do this?
Thanks for replying. The reason I want to try this is because there is a possibility I have a bad O2 sensor because when the car gets warm it misfires. I figured if I took it out of the loop, and the car runs OK, then I could narrow it down.
 

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try it for a short period to test.

misfire - is has the Opti spark been soaked or leaked on?
my 93 did from weep hole - strong coolant smell as well. replaced optispark whole thing with MSD, MSD ignitor, wires and new plugs. fixed no more issues.

but lets get to basics

check plug connections on block and opti.
how old is ignition on car? has ever been replaced?

could be something simple that's why i say start basic. if it is 02 sensor look up a good replacement, do not buy a 19.99 special
 

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Discussion Starter · #5 ·
try it for a short period to test.

misfire - is has the Opti spark been soaked or leaked on?
my 93 did from weep hole - strong coolant smell as well. replaced optispark whole thing with MSD, MSD ignitor, wires and new plugs. fixed no more issues.

but lets get to basics

check plug connections on block and opti.
how old is ignition on car? has ever been replaced?

could be something simple that's why i say start basic. if it is 02 sensor look up a good replacement, do not buy a 19.99 special
When you replaced your optispark, what were the symptoms? Did it have anything to do with engine temperature?
 

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car temps were ok a little high, i forgot to mention that i also replaced the paper thin radiator with a 4 row aluminum and all new hoses, temps dropped significantly.
my car was misfiring from coolant leaking onto it, opti didn't look great so replaced it along with ignition.
 

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So let's discuss o2 sensors and their operation. 02 sensors do not read the amount of fuel but rather they read the amount of oxygen in the exhaust system. o2 sensors operate in a range of mv from 0v(lean) to 1v(rich) with the midline being stoich or the point where all the fuel/air charge was completely burnt. In your OBD1 vehicle the o2 sensor is affecting Integrators(INT) and Block Learn Multipliers(BLM). The precursors of STFT and LTFT respectively. The o2 sensor can only trim up to 25% from the base programming one way or the other and only when the ecu is in closed loop. And it's adjustments will affect either 4 or 8 cylinders at a time. No factory application has the resolution to make changes to one cylinder alone based on a o2 sensor reading. Even today. For that control we either need a dedicated o2 sensor in each exhaust primary or we need to use an exotic solution like ionic sensing which has the resolution to measure per cylinder per combustion event fueling and also knock detection but requires an incredible control system. Ionic sensing works by running current across the spark plug on the exhaust stroke in a way that measures the level of ions in the exhaust as it leaves the cylinder. Ion sensing is so cool but not widespread. More can be seen on this here: Making sense of ion sense technology | Vehicle Service Pros

Your 1992 o2 sensor has just one wire. This one pin in the ecu for the o2 sensor is latched to a pullup resistor that shows voltage on that pin devoid of any ground. And the sensor itself gets ground from the exhaust it is screwed into. This is the same exhaust sensor that EFI started with in 1982. These o2 sensors have no fuse or 12v anywhere feeding them. If you wanted to take this o2 out of the loop for a diagnostic step you will simply unplug the 1p connector at the sensor itself and the car will run in base programming only and should stay in open loop.

Later on as we trend towards the standards of OBD2 o2 sensors will have 4 wires. These will be a dedicated feed and sense wire directly from the PCM for measuring the mv of the o2 sensor and there will be 2 wires that drive a heater circuit. The heater circuit is to help get the sensor up to temp faster so it reads accurately and can make the car start blowing clean smog sooner as per OBD2 spec. These heater circutis are fed by ignition power through fuses in the underhood fuse block and they get ground from the PCM so the controller can control o2 temp. OBD2 will also demand up and downstream o2 sensors for catalyst monitoring. When a fuse blows for a heater circuit on one of these vehicles the o2 sensor just takes longer to warm up but still works. And the biggest symptom of these problems is the check engine light that wont go out.

If your car runs ok when it is cold and develops a misfire when it is warm the first thing you should be scrutinizing is your ignition system. As spark plug boots get warm they might release tension on the spark plug and let the spark energy leak to ground from there rather than jump the air gap with a dense fuel mixture. This is easy enough to check for. Pull all your spark plug wires off the plugs and look for the white arcing evidence at the tips. Also the wires love to arc to ground or each other wherever they are close. Are there a lot of signs of arcing along your ignition wires? Are all of your ignition wires routed properly and away from the exhaust heat?

Opti spark problems are very frequent. They happen a lot and are quite common. However, they will usually lead you to a stall. When there is a problem with the ignition system affecting one cylinder we get a miss. When there is an ignition system fault present that affects all cylinders the motor cuts out like you turned off the light switch. While you should be checking for low or high res pulse failure codes in the PCM, your description sounds more like a bad plug or ignition wire than the optispark unit itself.

I also have questions about your temp. What temp are you seeing? When are you seeing it? And is this a change or has the car always ran warm like this? In these years GM was worried about oil temp more than coolant temp and not keeping it cool. When we don't let the oil heat up to the boiling temp of water we end up with rusty internals. GM wanted the oil temp to heat up for this effort so with the car sitting still and the A/C off the C4 might hit 230 or over before the fan high speed comes on. While we do not do that today this is proper operation for an early C4.

Also Griffin is a not so popular radiator company today and has been this way for a long time now downstream of the realization of the relation to coolant flow vs. airlflow. For anybody that adds all this thickness to the radiator the static pressure of their fans should also be increased just to make sure they will still get good airflow across a more restrictive air inlet. When we make the core of the radiator 4 rows thick the fans just disturb air and when the car is moving more air just flows around it. And so we should also retune the ECU commanding the fans to stay on to a higher vehicle speed. 3 rows is as thick as the industry will use today with high efficiency 2 row being the best. Not for price guys, But for the relationship of airflow vs. coolant flow. We must care about both together and not just throw one of the two to the wind.

We should also care about airflow across the condenser in front of the radiator with a bigger restriction behind it. Or maybe that is just a Florida thing.

And on the subject of coolant capacity. I have a few thoughts I want to share with everybody. Average underhood temps can dwell anywhere from 125f to 220f usually being somewhere right around the middle of that no matter where you are. The coolant coming in from the engine to be cooled can be up to 225f. And the cold tank of the radiator after it is cooled and before it goes back to the engine is always the lowest temp we will see under a hood aside from an A/C suction line. The act of passing through the core of the radiator is the only thing that drops temps. But once these temps are dropped as the sit in the tank they get warmed by the hotter engine bay just waiting to be used. The hope of greater cooling capacity equating to lesser engine heat DOES KINDA rely on the hope of storing that extra capacity at the lower temp, doesn't it? I mean if we think about it? Why have all this extra hot coolant? And why cool this extra coolant down if it is subject to the hot temps outside the engine? And this is the watershed moment that drove all the automakers to the size of their coolant systems as we see them.
 

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My result from my cooling upgrade engine temp or rad temp where ever it is monitored is down from 210 degrees to 190 degrees. Trans temp down to 170 degrees from 190 degrees. That’s running interstate at 80 mph. Up grades include three row aluminum rad, PRW high volume water pump and 180 degree thermostat and evens coolant. B&M auxiliary trans cooler.

When thrashing on it up in the tail of the dragon it runs about 210 engine temp 180 trans temp. Before upgrade it was running about 240 engine 210 trans temps. By thrashing on it I mean 11 miles in third gear up hill pushing for everything the LS 2 is worth. Have done it in second gear but the car whines up to high in the revs but it a holy terror of the corners. Oh it’s an 07 C6 base convertible.
 

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That's aggressive.

You should put dielectric grease in the 3p connector at your fan shroud if you haven't already or cut it out and hardwire It to help keep the 2 big pins from expanding from spending time with the fan over 85% duty cycle.
 

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Will do. Guy in our group has a C5 Z06 his fan runs 100% all the time and still has trouble over heating in traffic.
On my '04Z if it get 95*+ (which it can and will happen here in KY) and I have to idle for more than 10 minutes or so, mine will creep up to 225*-230* which is still okay with the ls motors. If it started going higher, I'd probably re-radiator like you did
 

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Will do. Guy in our group has a C5 Z06 his fan runs 100% all the time and still has trouble over heating in traffic.
My first thought there is does this guy have his air dam under the nose? The car shuts off the fans at a low vehicle speed. I think somewhere around 30mph in the stock tune. if this air dam gets destroyed or removed the air just skates under C5 and it runs at 240f out on the street. But can sit in a parking lot all day idling.

If he has his air dam and he verifies that both of his fans are working and on high speed and he is full of coolant and oil and as he drives the car it packs on heat, then it might be a good idea to look under the radiator cap for the coffee colored cheese.

On an engine at or above proper engine temp as soon as the water hits the crankcase it is turned to steam and rises to the roof of the crankcase. And so under the oil cap or under the PCV valve itself are the first places we will see the evidence of a failed head gasket even before the oil turns milky.
 

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Discussion Starter · #16 ·
If your car runs ok when it is cold and develops a misfire when it is warm the first thing you should be scrutinizing is your ignition system. As spark plug boots get warm they might release tension on the spark plug and let the spark energy leak to ground from there rather than jump the air gap with a dense fuel mixture. This is easy enough to check for. Pull all your spark plug wires off the plugs and look for the white arcing evidence at the tips. Also the wires love to arc to ground or each other wherever they are close. Are there a lot of signs of arcing along your ignition wires? Are all of your ignition wires routed properly and away from the exhaust heat?
Good stuff Autowiz. One followup...IF the plugs are arcing, would it kick on the check engine light when it misfires? My check engine light and the ASR light comes on when this starts. And, BTW, it always starts at about 195 degrees. Car never runs hot, and runs great when cold..up until that 195-200 degree mark.
 

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Discussion Starter · #18 ·
Do you have a scantool capable of looking at a datastream? I can help you with this diagnostic if you have resolution to see your datastream.
I don't, but if you can recommend one that isn't too expensive, I can get it maybe and go from there. But can a scantool show me what's happening while I am driving?
 

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your 1992 should show you a data stream. Albeit a very basic data stream. But it should let you see your o2 sensor mV reading and also your BLM and INT values along with coolant temp and some other basic things we can look at.

For example you could look at your o2 sensor value as live data. This should be expressed as a 3 digit mV value. Anything over 500mV is rich and anything under 500mV is lean. This value should constantly be jumping back and forth over this threshold. If this value stays at a high or low number there is a problem. Maybe not with the sensor or maybe with sensor. But this value needs to be constantly going back and forth from <400mV to >600mV.

Once in closed loop and warm you can look at your INT and BLM values. these are short term and long term fuel trims. The midline is 128. The controller adds to these numbers when it needs to add fuel or subtracts from these numbers when it needs to remove fuel. So if your engine had a vacuum leak and the o2 was always reading a low number because of this you might see this expressed on your INT and BLM values as them maxed out at 25% over that 128 midline which is 160. Likewise for an engine with too much fuel or not enough air we will see the number trend down to 25% less than 128 which would be 92. I forget which years started the 2 bank o2 sensors but if you have BLM and INT for each bank then it becomes easier to track your problems.

If your coolant temp sensor were unplugged you would see this in your data stream as -40f for the coolant temp value. This would be an important thing to see as it would be the reason your car would run rich when warm because open loop speed density fueling cares about engine temp. And when a engine temp sensor stays at -40 the controller will never hit closed loop. This would be a powerful revelation to see if that were your problem. With a simple and cheap fix, I might add.

If your inlet air temp sensor were unplugged or failed the same exact thing would play out as fueling is also based off of IAT and that sensor can fail and read -40 as well.

And a scantool like this will let you look at any diagnostic trouble codes. I really like using my Snap On scantools. I swear by them and have owned every generation since the red brick I started with. But if I were to chase after a cheap way of looking at data on an OBD1 GM vehicle, I might try something like this:
Amazon.com: OBD2 to OBD1 GM Adapter,OBD1 12 Pins to OBD2 16 Pins Diagnostic Tool Connector Adapter Cable Replacement for GM : Automotive

And use that with a scantool like this:
Amazon.com: LAUNCH CRP123X Elite 2023 Newest Lifetime Free Online Update scan Tool, SAS Calibration/Throttle Reset/Oil Reset OBD Scanner Diagnostic Tool, ABS SRS Transmission Car Scanner, Battery Test, Auto VIN : Automotive

There is cheaper out there, believe me but the cheaper you go the less functionality you get and the more lag there is to that live data you want to be looking at. With that said it will be a very tiny data stream you will be looking at so it might be ok to save money there. But Launch is also a known name in automotive diagnostics. Cheap price but not no name junk by any measure. I don't think.
 

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Discussion Starter · #20 ·
And a scantool like this will let you look at any diagnostic trouble codes. I really like using my Snap On scantools. I swear by them and have owned every generation since the red brick I started with. But if I were to chase after a cheap way of looking at data on an OBD1 GM vehicle, I might try something like this:
Amazon.com: OBD2 to OBD1 GM Adapter,OBD1 12 Pins to OBD2 16 Pins Diagnostic Tool Connector Adapter Cable Replacement for GM : Automotive

And use that with a scantool like this:
Amazon.com: LAUNCH CRP123X Elite 2023 Newest Lifetime Free Online Update scan Tool, SAS Calibration/Throttle Reset/Oil Reset OBD Scanner Diagnostic Tool, ABS SRS Transmission Car Scanner, Battery Test, Auto VIN : Automotive

There is cheaper out there, believe me but the cheaper you go the less functionality you get and the more lag there is to that live data you want to be looking at. With that said it will be a very tiny data stream you will be looking at so it might be ok to save money there. But Launch is also a known name in automotive diagnostics. Cheap price but not no name junk by any measure. I don't think.
Cool. Just wondering if the cable which is advertised as "OBD1" is actually what they call on my car the ALDL connector? Also, the scanner says it has coverage from 1996-2022. Does it matter that mine is a 1992?
 
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