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hi i am new to the fourm and also new to owning a 88 jeep comanche. i went to try and pass emissions and no luck. first time i went i got pass on hc fail co 26.45 actual, 25 limit. and pass on nox. second time after adding special additive to the fuel (which has always help my vehicles pass with flying colors) i failed again this time 25.51co. i really need to regester this truck and every thing that i look at seems to be fine.

i checked:


iat or mat as jeep refers to it



fuel injectors




changed oil

checked valve springs

when i preformed a vacuum test i found that it jwas bouncing between 17-19 at idle which is an indication of valve guide wear, no other signs are evident; i.e. smoke or fouled plugs.


it also has an intermittent miss that i can't pin to a cylinder.


truck has 150+ miles on it. i am really at a loss. any ideas would be great.

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