I have 1997 Ford F-150 V6 with a rebuilt engine. Mileage is unknown. I changed the spark plugs & wires, & air filter cause I haven’t done in about a year. I took it to get a smog check and it failed. The HC failed @ 25mph and just passed @ 15 mph. The NO failed @ 15 mph & just barely passed @ 25 mph. The CO passed @ both speeds.
Any advice on what I could do to figure out what the problem is and/or to fix my truck so it will pass smog would be much appreciated. Thanks in advance for any help.