Nissan Repair: 1988 Nissan Pathfinder: Not passing smog at idle, smog place, nissan pathfinder

Question
This is a tricky one...

I have a 1988 Nissan Pathfinder (v6, 4wd)with 160k miles and in
very good overall condition.  I live in California and it has not
passed smog, simply because the CO(%) failes at idle and idle
only.  All the other readings are excellent.  The CO(%) reading is
1.98 and max for California is 1:00

I have just replaced the O2 sensor, spark plugs, and Catalytic
converter.

The only other thing I can think of is the fuel injectors.

Can you offer any suggestions or advice.

Thanks!

Answer
Bill,

Double the CO is not good and usually caused by incorrect timing and too much fuel.  I would first check and adjust timing and make sure the idle is set correctly and install a fuel filter.

Now fill her up with premium and a bottle of CD2 and run the vehicle on the highway, with the air on and then go back to the SMOG place and you should pass.  Remember, that the hotter the engine is the less pollution it puts out.  Also, if you have not changed the oil change it before you go in for the test.  And, never take a cold engine in for SMOG.  Run it on the highway with all accessories going to get it nice and hot to burn all the crud out of the system before they put it on the machine.