I have a '97 F150 4.6. I just finished replacing head gaskets with fel-pro gaskets.

My problem is: I can't get the HC down enough to pass a California smog. All obd II codes complete with a pass. I checked the cats with a infrared thermometer. They're running around 600 in the front and 450 in the rear.

I can smell it running rich when I start it cold. I put new plugs, plug wires, obviously fresh oil, cleaned the map sensor, vacuum tested the egr, ran a tank of gas with some fuel treatment and ran the truck up and down the freeway before testing.

Can anybody give me some advise that might help me pass the smog check?

 

Check the fuel rail pressure sensor. Pull the vacuum line and see if any fuel comes out.

 

check to see if it is throwing any codes, will tell you if you have a bad oxygen sensor and so on.

 

everything comes back complete and pass. That's what puzzles me!

 

My intuition is telling me that it could possibly be a fuel delivery or a compression problem. Compression check is a four hour labor rate job (that's what I was told), so I'll take your advise...

 

I'd take it to another smog ck shop just to see.

 

Try cleaning your MAF sensor.

 

High on HC means ignition problems.

 

Bill is right, Ignition or possible lean mixture. The pressure regulator would cause high CO. I've been away from it to long.

 

I have new autolite plugs gapped to .052 brand new, and brand new plug wires. I guess I can check the coil. Any other recommendations?