O2 sensor eliminator — why?

[ChipBeck_imp]

I also would recommend checking the TPS sensor position as someone else suggested. It is a 3 wire potentionometer which has a 5 volt reference signal provided by the ECU. It's function is to let the ECU know what type of load the engine is under along with the MAP sensor. Under conditions of light load and high manifold vacuum ignition timing is advanced as the flame front travels slower. On both my bandit 1200 and Bonneville the TPS was out of adjustment. Not sure on the CB but on those bikes just losen 2 screws and rotate the TPS. Made a nice improvement in off idle response.
O2 sensors today seldom go bad. It is a long shot but an exhaust leak can cause what is called a false lean reading. As the exhaust pulses pass the exhaust leak the resulting low pressure zone will pull in fresh air. The O2 sensor will see this and send a low voltage signal to the ECU. To check hook up a multimeter to the O2 sensor and use propane to see if the voltage signal consistently stays above or below .5 volts. This is the shade tree method but I never could justify the 5 grand for a 5 gas analyzer. You want to use the pre cat O2 sensor for this.
Good luck. Drivability issues can be maddening but it is fascinating I think to try and figure out the issue and very satisfying when fixed.

Gentlemen,

I was going to write this exact same thing but Toro beat me to it. Darn!!

Chip

[Toro5xi_imp]

I would really like to hear the result when Guth gets this corrected. Most of the drivability work I have done has been with cars and without the factory information it would have been tough to know what to correct. I would think if these issues have been reported before Honda would have a fix such as a new fuel map or timing chart to down load.
I agree with Guth that eliminating the O2 sensor may not be the best long term correction. in closed loop operation the O2 sensor provides important information to the ECU so that it can maintain the proper air/fuel ratio. In the old days we would mask these problems by dumping more fuel into the motor by putting a hole in the MAP sensor tube so the ECU saw less vacuum and thought the throttle was open more than it was thus the injector pulse width was increased. This worked for a while but resulted in higher levels of pollution and I often failed emission testing.
If it was not raining in Cleveland Ohio all day I would be riding instead of rambling on. Sorry

[Chapomis_imp]

ACK, you following this ???

[ChipBeck_imp]

I would really like to hear the result when Guth gets this corrected. Most of the drivability work I have done has been with cars and without the factory information it would have been tough to know what to correct. I would think if these issues have been reported before Honda would have a fix such as a new fuel map or timing chart to down load.
I agree with Guth that eliminating the O2 sensor may not be the best long term correction. in closed loop operation the O2 sensor provides important information to the ECU so that it can maintain the proper air/fuel ratio. In the old days we would mask these problems by dumping more fuel into the motor by putting a hole in the MAP sensor tube so the ECU saw less vacuum and thought the throttle was open more than it was thus the injector pulse width was increased. This worked for a while but resulted in higher levels of pollution and I often failed emission testing.
If it was not raining in Cleveland Ohio all day I would be riding instead of rambling on. Sorry

Toro,

Joking aside, your posts are really good stuff though a bit beyond my comprehension. I have one question. If it is the throttle position sensor, why would eliminating the 02 sensor fix Guth's drivability problem? Why would getting rid of that sensor fix any other problem?

Chip

[Toro5xi_imp]

I am speculating but I think that with the O2 sensor eliminated the computer is operating in open loop. In open loop the computer uses predetermined fuel maps which are slightly rich. The 2 main systems are speed density or mass air flow. With speed density the main inputs are RPM and Manifold Absolute Pressure. Mass Air flow uses a meter to actually try and measure the mass of air entering the engine. When the O2 sensor reaches 600 degrees the system goes into closed loop and primarily uses the voltage from the O2 sensor to adjust what is called the fuel trim to achieve 14.7 to 1. I am going off memory and I am sure it has advanced since I worked on this stuff. In open loop the fuel tables are slightly rich which is why the auto companies try to get the car into closed loop as soon as possible. This drove the need for O2 sensors with heaters in them. Rich can mask a lot of issues but creates more pollution. It could be that in closed loop one of the sensors like the engine coolant sensor is faulty.
I am still leaning towards the Throttle Position Sensor but it is hard to know. On my Bandit 1200 the TPS effected ignition timing only. I do not know if Honda is also using it to effect injector pulse width.
This is where I think the dealer would be the most help. There may be a technical service bulletin but at the very least they have flow charts which will guide the technician in his diagnostic process.
I just looked at the Power Commander site and it does state the Sensor eliminator prevents the ECU from going into closed loop operation. Hope this helps. I think some of the earlier posts did a great job explaining closed loop operation as well.

[SanPete_imp]

Here I was thinking I am an accomplished mechanic by doing my own oil change. What did he say?

[Toro5xi_imp]

Without the schematics and scan tools I think it is very tough to work on the electronics anymore. The dealer technicians also work with it everyday and stay up to speed with the latest advancements and information. I happily leave electronic trouble shooting to those guys now.

[ChipBeck_imp]

I am speculating but I think that with the O2 sensor eliminated the computer is operating in open loop. In open loop the computer uses predetermined fuel maps which are slightly rich. The 2 main systems are speed density or mass air flow. With speed density the main inputs are RPM and Manifold Absolute Pressure. Mass Air flow uses a meter to actually try and measure the mass of air entering the engine. When the O2 sensor reaches 600 degrees the system goes into closed loop and primarily uses the voltage from the O2 sensor to adjust what is called the fuel trim to achieve 14.7 to 1. I am going off memory and I am sure it has advanced since I worked on this stuff. In open loop the fuel tables are slightly rich which is why the auto companies try to get the car into closed loop as soon as possible. This drove the need for O2 sensors with heaters in them. Rich can mask a lot of issues but creates more pollution. It could be that in closed loop one of the sensors like the engine coolant sensor is faulty.
I am still leaning towards the Throttle Position Sensor but it is hard to know. On my Bandit 1200 the TPS effected ignition timing only. I do not know if Honda is also using it to effect injector pulse width.
This is where I think the dealer would be the most help. There may be a technical service bulletin but at the very least they have flow charts which will guide the technician in his diagnostic process.
I just looked at the Power Commander site and it does state the Sensor eliminator prevents the ECU from going into closed loop operation. Hope this helps. I think some of the earlier posts did a great job explaining closed loop operation as well.

Toro,

3 more questions.

1. So the CB11 should get slightly better mileage with the 02 sensor working right?

2. Is it the 02 sensor that leans out fuel to keep the bike at 14.7 to 1 in the thinner air at high altitude?

3. Would a CB11 ever run poorer with the 02 eliminator or would it just run slightly rich sometimes?

Thanks.

Chip

[Toro5xi_imp]

The absolute best performance occurs at a slightly richer mixture than 14.7 to 1 but this will result in higher levels of carbon monoxide in the exhaust stream as there will not be enough oxygen atoms to combine with all the carbon and CO readings will be elevated as seen by the 5 gas analyzer.
"immgunn" said it well in his earlier post. As fuel pumps weaken or air leaks occur the O2 sensor reads the amount of oxygen in the exhaust and is constantly trying to alter the fuel ratio to eliminate Hydro Carbons and NOX. This makes the EPA happy but weakens performance but only slightly.
Engineers spend a lot of time creating fuel maps but it is a compromise and their primary objective is to satisfy the EPA. After market tuners are more concerned with performance and want to provide a margin of error as well. Lean conditions are dangerous as they lead to higher combustion temperatures. After market tuners richen up the fuel maps and turn off the O2 sensor as they do not want the ECU to take control and try to achieve the 14.7 to 1 ratio again. This would ruin all the time they spent creating the fuel maps.
If anyone is interested JD Halderman has some great books on drivability and electronics.

[Guth_imp]

My family probably wouldn't be too thrilled with me if I were to start spending my nights at a Holiday Inn Express, but clearly it's been paying off for Toro.

Toro all joking aside, you're contributions to this thread are truly appreciated. I've got enough wrenches and such that I can get myself into plenty of trouble, but I don't have anything like the complex scan tools that you made mention of. In all honesty don't find working with electrical issues to be nearly as fascinating or as rewarding as I do simply working on the mechanical side of things. But I do like to be informed about what is happening with the inner workings of my bikes and that is where posts made by yourself and others come in so handy.

As I don't have the tools to take this any further, I'll update this thread after I've had a chance to get things looked at by the guys at my local shop.