I got a 1984 monte carlo ss with the stock 305 with aftermarket headers. The car was running rough so I took it to the mechanic and he said my spark plugs were fouled because it was running to rich. After the spark plugs were changed its been running great. I was told to add a 02 sensor to make it run better I read I could add a 3 wire 02 sensor welded to the exhaust were do the sensor get connected to? What wires go were and can I just use a universal o2 sensor ?
O2 sensor
- Thread starter SSmooth84
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If you're running the CCC carb and distributor on it without an O2 sensor, you're just pi$$ing in the wind. You need ALL your CCC stuff operational for it to work correctly. Without the O2 sensor, it may idle fine in OPEN loop conditions, but when it goes to closed loop, the carburetor has NO IDEA what fuel ratio is needed to adjust the carburetor tuning. Pi$$ing in the wind.
If you've changed all that junk to non-CCC stuff, then you need someone who knows how to actually tune a carburetor and vacuum advance distributor. If you did NOT change out anything else other than the headers and kept the CCC stuff, you will need to add preferably a heated O2 sensor that would go in the collector, at 3:00, 9:00 or 12:00 position is considered the best locations by people that do this, whichever can fit. Just no bottom feeder locations. Then get an adapter plug in harness for it. I believe the O2 sensor stock wiring is on the driver side on the 305??? I can't recall. Anyway, if it is, just put your bung on the collector on whichever side the factory one was on so the wiring will be within easy reach.
Heated O2 sensor (GM/Delco AFS74):
Adapter harness (red wire to an ignition ON 12v source, black wire to ground, and plug the plastic connector into the factory single wire harness):
Good luck.
If you've changed all that junk to non-CCC stuff, then you need someone who knows how to actually tune a carburetor and vacuum advance distributor. If you did NOT change out anything else other than the headers and kept the CCC stuff, you will need to add preferably a heated O2 sensor that would go in the collector, at 3:00, 9:00 or 12:00 position is considered the best locations by people that do this, whichever can fit. Just no bottom feeder locations. Then get an adapter plug in harness for it. I believe the O2 sensor stock wiring is on the driver side on the 305??? I can't recall. Anyway, if it is, just put your bung on the collector on whichever side the factory one was on so the wiring will be within easy reach.
Heated O2 sensor (GM/Delco AFS74):
Amazon.com: GM Genuine Parts AFS74 Heated Oxygen Sensor : Automotive
Buy GM Genuine Parts AFS74 Heated Oxygen Sensor: Oxygen - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
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Adapter harness (red wire to an ignition ON 12v source, black wire to ground, and plug the plastic connector into the factory single wire harness):
TPI TBI 3 Wire Heated Oxygen O2 Sensor Wire Harness Adapter Camaro Corvette 4ft | eBay
For TPI TBI and Many other Chevy/GM Cars. With this you can install a heated 3 O2 sensor in place a of a 1 wire O2 sensor. Wiring plugs into your factory connector. Very easy to install. To be used with AC Delco part number AFS74 or an equivalent O2 sensor(WALKER makes one for a little cheaper).
www.ebay.com
Good luck.
I am still running the stock carburetor with the stock distributor and still have the computer i haven't remove that. It runs fine and gas milage is not too bad can someone post a pic of were the signal wire hooks up i can do the ground and ignition just no sure were the main signal connects to .
Rhetorical question- if it runs so fine, why do you foul plugs or need a heated O2 sensor? There should be a single wire with a tubular style black plastic connector on the end somewhere near the rear of the engine coming out of the engine wiring harness that makes its way over to the underneath of the HVAC housing going to the ECM. Probably a purple wire?
There's a reason it's there, and if you're not in closed loop, which a hot O2 sensor gives you, your overall gas mileage and performance suffers. The car basically stays in open loop, which is fine if you're waiting for a Big Mac in the McDonald's drive through, but not cruising down the highway. Are you not throwing codes?
There's a reason it's there, and if you're not in closed loop, which a hot O2 sensor gives you, your overall gas mileage and performance suffers. The car basically stays in open loop, which is fine if you're waiting for a Big Mac in the McDonald's drive through, but not cruising down the highway. Are you not throwing codes?
Being an 84, what he has is not a computer such as what cars run now. it is a first generation controller, an ECM or EEE and everything in it is a preset that responds to input from the sensors. Generationally it is termed an OBD I. There is a plug in for it located under the dash on the driver's side but you need an OBD I class reader to make any kind of use of it. I have an OBD II reader made by Bosch from OTC that has the series one software also on board but it is so primitive that even if you try to read an old type I you are lucky to get anything useful. I don't recall finding or seeing an O-2 bung on the original pipes that I found in my 85. The ECM was there, but it was a corpse, DOA and disconnected from the wiring harness down at the starter. The post mortem found major corrosion internally from salt invasion, probably off the boots of the various passengers that rode shotgun during the winter years.
He is lucky to have scored a car that still has the stock system intact and operational. For myself I would say leave well enough alone in terms of the system and maybe, just maybe, go up one number from stock in the plugs; e.g. from an AC R44TS to an AC R45TS or, if his plugs are suffixed TX, from the recessed electrode to an exposed one, suffix TS, to obtain a more complete air/fuel burn. He doesn't have to be using the AC's, they are simply what I have on the bench by way of example and whIch I used to use with an old motor that did lots of short runs and idled a lot. The hotter plug with the longer electrode might help reduce the fouling if a lot of the driving he is doing is short distance with lots of idling and stop and go included; like a morning commute to work!
One caveat here. If it turns out that the fouling is due to other issues such as an oil control problem, then nothing short of new rings or valve seals/knurled or replaced guides can help that.
He is lucky to have scored a car that still has the stock system intact and operational. For myself I would say leave well enough alone in terms of the system and maybe, just maybe, go up one number from stock in the plugs; e.g. from an AC R44TS to an AC R45TS or, if his plugs are suffixed TX, from the recessed electrode to an exposed one, suffix TS, to obtain a more complete air/fuel burn. He doesn't have to be using the AC's, they are simply what I have on the bench by way of example and whIch I used to use with an old motor that did lots of short runs and idled a lot. The hotter plug with the longer electrode might help reduce the fouling if a lot of the driving he is doing is short distance with lots of idling and stop and go included; like a morning commute to work!
One caveat here. If it turns out that the fouling is due to other issues such as an oil control problem, then nothing short of new rings or valve seals/knurled or replaced guides can help that.
The car runs good and I did the paper clip to check for codes and that was coming up since it don't have a o2 sensor. The mechanic said because its running rich without the o2 it will keep fouling up the spark plugs. I'm looking for a a pic of that purple wire thats in the engine bay from were it runs from the harness.
The O2 sensor was in the drivers side exhaust manifold. See red dot in picture, there is a plug in the O2 sensor hole in the pic. Wire if still there will be in that area.
Since you installed headers you need to see if the headers have a hole for the O2 sensor and if not you need to make one and weld a bung onto it as 69 hurstolds outlines above.
. Likely have to lengthen the wire to it too.
Since you installed headers you need to see if the headers have a hole for the O2 sensor and if not you need to make one and weld a bung onto it as 69 hurstolds outlines above.
. Likely have to lengthen the wire to it too.
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You are right I'm going to have to get a bung welded on the exhaust. I read the 3 wire was better than the single wire and needs to have power, signal, and ground. I'll be checking the car for the purple signal wire tomorrow.
The band-aid of changing plugs will just be an oft-performed ritual without that O2 sensor. And I can't disagree with you more on the fact that the OBD1 ECM is just a complete preset box of parameters. Plus, without the O2 sensor, it isn't intact and operational. If you try to run your car without changing out the parts that input/are controlled by the ECM, then your car will overall run like crap. Period. If you fix it, you'll be surprised how much better your car runs with everything working in harmony. You can't change fuel mixtures as fast as the slowest OBD1 ECM if it's working correctly. This is one area where many people, still to this day, don't understand why you must use an O2 sensor in your exhaust system if you continue to use the rest of the CCC system.
And yes, there's a few things you can do that won't wack out the CCC system. Like the removal of that A.I.R. system. While you don't absolutely have to have it, it's there for a reason. Lower tailpipe emissions by injecting air into the exhaust to complete the burn as it were. Note too, it pumps air to the second half of the catalytic converter. If you do remove it, then plug every vacuum line. With headers, you're likely to be tossing the cat as well anyway, so that's no longer a factor.
At minimum, to bypass the ECM, you would need to change out your m/c solenoid controlled carburetor, and your electronically controlled distributor to non-CCC types if you're tossing the O2 sensor. Otherwise, you're stuck with an open loop CCC where vacuum and temperature only are controlling fuel mixture. Which isn't optimal, as you can see by your plugs. You're making the computer guess.
The connector part number listed above has 4 ft wiring on it that should give you plenty of wire to be able to hook it up.
If you're looking for the end of the wire that connects to the O2 sensor under the hood, look for a single round pin that has that light green, rubber weatherpack connector seal on it. It also will have a clip on the side that clips over the tang on the O2 sensor wire. It may be a brown wire, not purple as I originally was thinking. I think the purple is on the O2 sensor side of the connection. It is for Delco O2 sensors, anyway. Which is the only brand I'll ever use on my G-bodies.
And I still, and always will, stand by my statement of pi$$ing in the wind if you don't do an all or nothing on the CCC system concerning the carb/distributor/O2 sensor on a G-body.
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