I have a 2005 Explorer Sport Trac 4.0L V6 that fails emissions for high HC at idle. I have already replaced upstrem and downstream 02 sensors, air filter, gas cap, EGR module and PCV valve. OBD II reader shows no DTC's and green light shows indicating all emission systems are working. The initial test showed HC at 102 ppm, for which the Calif. standard is<100ppm. Also seems to have a smell of unburnt fuel. After all the repairs above HC actually went UP to 147. Anyone have any ideas?

 

have any idea where your fuel trims are at?

 

When were the plugs and wires last changed?

 

No idea where the fuel trim tabs are.

 

Last changed plugs and wires withnthe last 30K miles.

 

you need a scanner with live data to see the fuel trims.

the only other thing I could think of, is the car a CA car or bought elsewhere and taken to CA. The reason is I know mine could pass PA but probably not CA with their higher standards.

 

The catalytic converter might be worn out. Easiest test is temperature, using a non-contact pyrometer (aka laser thermometer). After running it at operating temperature for a while, check the temperature of the exhaust pipe before and after the converters. It should show a 100f rise after the converter.

 

What was your CO number? A bad cat will fail the CO, not just HC.

A California smog test checks to see if it's a CA or Federal vehicle, and tests to that standard. In 2005, they may have been the same.

Is there a slight miss at idle?

Have you ever had the intake gaskets replaced? A leaking intake gasket might give you a slight miss, and therefore some unburned fuel. Idle usually has the highest vacuum, making the problem show up there but not under the higer rpm test.

Why did you replace the gas cap? You passed the evap part of the test, right? Speaking of evap, do you overfill your tank when you fill up? That will flood the evap system, another possible here, although I think probably a long shot.