My stock 94 Accord is failing for high CO, the car was putting out .93 and the max allowed is like .62. I can't really figure out why it would be so high.

I think it could be my cat, but it's only 1 year old, so I'm doubting that. I don't see any reason for the motor to be running rich, other then maybe a lazying 02 sensor. I really don't have a money to dump out for a new cat and new o2.

I tried Guarenteed To Pass and it knocked my reading down from .95 to .93, but that was also three days after it was all out of the car. I might try it again to and go to testing with it in my tank.

Any suggestions?

 

High CO is usually caused by air obstruction. Check and replace your air filter.

 

A dirty air filter is not going to cause a fuel injected engine to run rich.

 

I have a SRI, I don't think that it would cause it to run rich, maybe a tad bit leaner if anything.

I was thinking of going back to stock intake for now, but the filter was ruined and my local supply store was out. Would it make that much of a difference? I'm stumped

 

Do you know how to monitor O2 voltage with a voltmeter? If your O2 voltage toggles at cruise or wherever it fails then your feedback system is working properly and you likely have a bad cat.

 

I'm not sure how. I'm gonna take a guess and say have somebody bring it to 2500RPM in park, I put the voltmeter to the power wire and see if it jumps?

 

No, you need to put one lead of the voltmeter on the O2 signal wire and the other to ground. The reading should toggle between 0 and 1 volts pretty rapidly. At what RPM did it fail and what were the readings?

 

2500rpm on the rollers. My car blew a .92, max is .73

 

Does your car have mods?

 

Generic SRI and new NGK G-Power plugs.

Bone stock otherwise

 

Neither of those will cause it to run rich. Obviously I can't know how your car runs and what direction to go in but I would be suspecting the cat assuming the car runs well. If it came into my shop the first thing I would check was to make sure the feedback system is working as designed and then I would check the cat with my infrared pyrometer. The inlet to the cat should be cooler than the outlet. In most cases a 100 degree F difference indicates that the cat is working properly.

 

yeah make sure the cat is warm too, they gotta be at operating temp for catalyst to be efficient.

 

Warmed up the car, and it's a 20 minute drive to the inspection station, plus I left my car running while I waited 10 minutes in line. The thing is the cat is 1yr old, the only way I could see it being bad is if I've been running rich since it's been replaced, and it ate the catalyst away.

Tomorrow in school I'm gonna take it to the shop and look at it under the lift. I'll see if maybe the bolts are loose or something, which might make a big temperature difference as stated. Also gonna do the voltmeter testing.

 

What school are you going to?

 

I'm still in high school...lol.

Pemberton Township in NJ

 

Usually High CO indicates a rich mixture. what was your HC and NOX at? what was your CO2% at?

usually high CO would be caused by a dirty/plugged air filter, plugged pcv valve, or dirty oil.

 

yes a bad air filter will cause high CO. Checking voltage on an O2 with a voltmeter is not gonna help you at all, if u want to check you readings on a 02 sensor you will need a oscilloscope or a snap on vantage scanner to check your readings. Voltmeter wont give u an actual reading.

 

When testing the O2 to determine if feedback is working you do not need an actual reading. You are checking to see whether the fuel mixture is toggling between rich and lean. You can use a digital volt meter. The reading on the O2 sensor signal wire should toggle between 0 and 1 volts (in actuality you will see about .1v to about .9). As long as the voltage reading is toggling quickly you know that the computer is reacting to the signal it sees from the O2 sensor. A low voltage, say .1v, indicates a lean fuel mixture and a high voltage, say .9v, indicates that the mixture is rich. If the O2 voltage is stuck high, anywhere above about .5v, you know the mixture is rich. If it is stuck low, below .5v, you know the mixture is lean (assuming the O2 sensor works). If you were to remove the cat from a perfectly running car it would not be unusual to see .9% CO. The cat cleans it up enough to bring it within limits. An air filter would have to be really, really dirty on a fuel injected car for it to cause the mixture to change enough to cause it to fail. On a carbureted car, however, a dirty air filter can 'choke' the carb and cause it to be rich.

Like I said, if I saw that feedback was working properly the first thing I would do is check catalyst efficiency.

 

My car passed lol. Didn't do another thing to it. Motor vehicle said the car just might not have like the cold.

In response though, oil was changed, and the filter was clean. HC + NOX were wayy below MAX limits. I took it back for the third try, and it went with flying colors haha

 

Good, problem solved for now.