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-   -   Troubleshooting fuel mixture (http://www.focusfanatics.com/forum/showthread.php?t=301717)

Farking_farkus 11-07-2012 06:44 PM

Troubleshooting fuel mixture
 
I have a P0420 code (insufficient cat efficiency) and am trying to isolate the problem. Car idles, drives fine. I do hear very slight emission backfire at 40-50 mph, but hardly can hear it over the radio. I replaced wires, plugs, coil pack recently, and I'm gonna check the injectors tomorrow (with ohmmeter). I think the fuel mix may be a tad rich. Any other suggestions? From what I've read, the O2 sensor is usually not an issue.

http://www.obd-codes.com/p0420

6SPD_soul 11-07-2012 07:19 PM

It might be more likely that your cat is just no longer doing it's job. You saw from that site you listed that the front sensor should fluctuate fairly quickly between 0-1V (actually more like .2ish-.8ish) DC and the rear should have a pretty steady and consistent reading of .5V DC. This can be pretty easily checked with a voltmeter/multimeter, but you'd need a wiring diagram to tell which wires to backprobe at the o2 sensor connectors. Two will have to do with the heater circuit and the other 2 will have to do with the signal the PCM is looking at.

I think this would be best way for the average guy to look at what the o2 sensors are doing. There're probably youtube videos that'd show you how to do this.

zetecDon 11-08-2012 06:46 AM

Moved to "General Technical Chat".


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