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Truck throwing rich code


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bob8619
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Apr 24, 2012, 8:28 PM

Post #1 of 8 (1113 views)
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1995 Ford F150, 5.0 V8 automatic. Been having the code 173 which is running rich. The check engine light doesnt come on for this code but when I run a test it is in the KOER results. The exhuast does NOT smell of gas, there is no black smoke, the spark plugs are very clean maybe even TOO clean. Is it possible that it runs rich without ANY of those things happening?


Discretesignals
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Apr 24, 2012, 9:09 PM

Post #2 of 8 (1098 views)
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On something like that you would have to watch the O2 sensor voltage. If the voltage stays above .450mV, the sensor isn't detecting much oxygen in the exhaust which the computer indicates as a rich fuel mixture condition. When this happens the engine computer takes fuel away from the engine in hopes of correcting the rich condition.

If the sensor is reporting rich, you can create a vacuum leak to see if the sensor swings lean. If it swings lean, you know the sensor is good. If the sensor stay rich even if you create a large vacuum leak, the sensor is stuck rich and needs replaced after verifying the intregrity of the O2 sensor wiring and the heater voltage.

Once you determine the sensor is reporting correctly, you need to determine why the sensor is reporting rich. Questions you would have to ask yourself are do I have excessive fuel pressure, leaking injectors, fuel tank vapor recovery system problems, MAP sensor reporting high manifold pressure, MAF sensor reporting more air going into the engine than there actually is, etc.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Apr 24, 2012, 9:14 PM)


bob8619
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Apr 24, 2012, 9:14 PM

Post #3 of 8 (1088 views)
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Oh I forgot to mention today based on how I believed the oxygen sensor was the original I replaced it, so thats new, the ECT sensor is new and I put a new air filter in today as well. I happened to break some vacuum tube while checking the plugs so what your saying is with that vacuum leak it should stop being rich? Is there ever a time when it can throw a code like that but be false?


zmame
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Apr 24, 2012, 9:26 PM

Post #4 of 8 (1077 views)
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Just out of curiosity you are doing the KOER test when it's at operating temp?


Discretesignals
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Apr 24, 2012, 9:28 PM

Post #5 of 8 (1076 views)
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You going to have to monitor the O2 sensor voltage on this one with a volt meter or oscilloscope to see what exactly is going on. Won't know what direction to take with this unless you monitor the voltage first. Not only should you monitor the voltage at idle with the engine warmed up, but also monitor the voltage with engine at 2500 rpm.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


bob8619
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Apr 24, 2012, 9:30 PM

Post #6 of 8 (1069 views)
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Yeah engine was hot when I do the test. After replacing the air filter it has been giving the rich code 173 OR a code 311. Never both at the same time either one or the other. And it kind of alternates back in forth like one test is one code next test is the other code.


bob8619
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Apr 24, 2012, 9:32 PM

Post #7 of 8 (1065 views)
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Oh and as far as testing the o2 sensor, can you point me in the direction of some place that has a how to on how to check that and what the proper readings should be?


Discretesignals
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Apr 24, 2012, 10:09 PM

Post #8 of 8 (1051 views)
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To tap into the O2 signal watch the video. The video gives you the idea of what the signal is going to look like on a good sensor and good running engine.

http://www.youtube.com/watch?v=uYMGnvtgi8w





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Apr 24, 2012, 10:10 PM)




Truck throwing rich code


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