NOX emission failure-'94 Jeep grand Cherokee

Old 02-02-07, 08:52 AM
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NOX emission failure-'94 Jeep grand Cherokee

I have excessive nox emmissions which caused a failure on the state safety sticker test. What could be the problem, Cat. converter or Oxygen sensor.
Old 02-02-07, 09:25 AM
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Neither. I'd look into things like EGR valve, cooling system and or what type of fuel being use.
Old 02-02-07, 12:12 PM
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It coiuld be the EGR like New Guy said, but, it can be many other things as well. Like the O2 sensor or cat. The 02 sensors are more likely then the cat. If there were a 02 sensor problem, the check engine light "should" have gone on though. I don't think a EGR valve on a OBD1 vehicle car like yours would throw a CEL, so, change that EGR valve out, which is usually pretty cheap and easy. Make sure you have good, clean oil, fill the car up with 93 octane, or 91, drive vehicle for about 20 mins before you bring it back to get inspected.
Old 02-02-07, 05:32 PM
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would probably look at the egr first you should be able to test it with a hand held vacum pump with the engine running open the valve the engine should run very rough or may even die then check all the vacum lines going to the valve.
would suspect an o2 sensor would cause most all vehicles to have excessive carbon monoxide or hydrocarbons also and not just fail on nox only.

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