I have a 1994 Ford Ranger, 3.0l that fails NOx. The HC and CO look Good Numbers are as follows: HC 1.06 limit of 4.41 CO 22.03 limit of 71.17 NOx 4.02 limit of 3.94 My question is this vehicle does not have an EGR system at all, and Ford tells me that some of ... Login to read more.