passed emissions test but hydrocarbon output was at the limit, so i want to fix that for next time,because it'll probably be worse by then...any ideas????360 magnum 176000miles

 

What's the condition of plenum gasket, cat and o2 sensors? Last tune-up? Any vacuum leaks?

 

plenum is fixed, engine runs good, did a complete tuneup not to long ago...cats fine and o2 is too... NO check engine light

 

How old is the cat?

 

probably original

 

Uh huh.

 

I'd put my money on you needing a cat and some ntk o2's...if you wanna get a better score on the E-test

 

the e test as u call it, tests for 3 diff chemical levels... which are hydrocarbons, carbon monoxide and nitrogen oxides... the hydrocarbon out put in my truck is higher than the last test the cat is as good as it was last time, the cat is just a band-aid that the gov put on vehicles... my original question was for possible reasons for high hydrocarbon output, meaning what could be wrong with my engine to be causing the high hydrocarbon levels...

and y the **** in 50% of these threads is there a post saying the problems the cat, its clogged, its to old

o and by the way its a 94, theirs only one o2

 

High HC means a lean running engine or a cat that doesn't do its job.
Which is why I asked about the plenum, ignition supply, and vacuum leaks. And the cat.

...Because these trucks have a known problem with plenum gasket failure which leads to cat failure among other things.

Idk I might be thinking irrationally here but bear with me. You had a plenum failure which is known to ruin cats and o2s. Then you fixed the plenum and not the cat and o2 sensors.

 

They dont last forever.
Plenum issues and original
Cat and O2 sensors being poluted
by a bad plenum plus 176000 miles.
Might be a good place to start.
There it's been said.