a rich condition means that the O2 sensor is detecting that you have a lot more "raw" fuel coming out of the engine than you should. If you have a weak spark it's only going to partially burn or fail to ignite at all (a missfire) that results in the blowby.... and partially burned gas can be from the injector leaking a bit and dumping in to much OR a weak spark, or both.

Both: Your injector starts leaking a bit, fouls the plug, now the plug isn't igniting properly and you're blowing out a lot more unused fuel...

 

The o2 sensor does one thing: It detects oxygen. No matter what else comes though the exhaust system, all it sees is the oxygen.

 

if it recodes start with checking fuel pressure.

 

Thanks for the replys. I will try to find a way to test the fuel pressure on it, but that adapter on the fuel rail isn't the standard schrader (sp?) valve.

I remember reading that you can fabricate one by drilling a hole through a bolt with the proper thread pitch and basically attach a hose/gauge on the other end. I would rather buy the proper adapter, but I'm not sure where I can buy one?

 

sorry, i didn't realize you were a difference poster from the op(rough day, [8D]). 43 = o2 sensor 95% of the time. so if it recodes slap a new one in there if you don't have a dmm and can't test it. if it recodes again, check fuel pressure.

 

The O2 sensor is about a month old, so I can recheck the resistance with my DMM. When the O2 sensor went out, the code as 41 (O2 sensor circuit).

I was curious to the cause of a code 43 the other 5% of the time.

I understand where a weak spark or leaking fuel injectors would cause the car to run rich, and those are easy to correct. Testing the fuel pressure seems pretty straightforward, I just don't have an adapter that will hook on to that goofy valve on the fuel rail.

 

resistance check? did you mean voltage check?

 

His earlier code 41 is the sensor heater, that would be a resistance check. Code 43 is a different failure mode for the sensor.

 

Around christmas, I got a code 41 and the resistance was way off. I replaced the O2 sensor. A couple of days ago, the CEL came on and got a code 43. Cleared ECU and it hasn't returned. Since the O2 sensor is new, it "should" be ok. The test procedure for a code 43 requires a test harness that I do not have to figure out the problem with the O2 sensor.

I was asking what problems on the fuel supply side of the code could cause the problem. I can test the fuel pressure, but I need to either buy or rig an adapter for the M12x1.25 threaded hole on the fuel rail.

 

I have a 1991 Honda Accord EX with 200K miles and had been getting code 43 for the past 10 months on and off. I would experience generally at highway speeds a moderate loss of power for maybe 10 seconds and would clear up right when the Check Engine light came on. This would happen about 40% of the time the CEL came on. Replaced O2 sensor in Feb 2014 and again in April 2014. Both times code was cleared and had no check engine light for 3K miles. Came on again recently after another 3K and mechanic found oil had been running down the line and into the O2 connector. He bent the wire a bit so that the oil will not run directly into connector until the leak is fixed. Car runs fine now. Will check in in another 3K to say if it was a permanent fix.