Just did my smog test, I wonder if anyone can tell me why my HC is high. Any help would be appreciated. Thanks in advance. 1994 2.3L man trans.

 

Replace upstream O2 sensor, they are the only sensors that wear out at 100k miles or 12 years old
These cause the engine to run Richer than it should which cost you money in wasted fuel, so they pay for themselves over the next 100k or 12 years

Oil burning
Check spark plug tips, look for signs of oil in the cylinders

High HC means too much fuel or oil is not being burned up all the way, incomplete combustion
1994 doesn't have adjustable spark timing, which is another reason for higher HC, out of time spark on older vehicles

Low compression
If timing belt is older then compression may be lower, another reason for higher HC

 

Thanks Ron.

 

Hi Ron. Just replaced my O2 sensor. I replaced with a BOSCH one, hopefully it would last the next 100K if the truck can make it that far. Lol.

BTW, I have a quick question. To fit my tool on the O2 sensor, I had to loosen one bolt (bottom) at the exhaust pipe that connects to the exhaust manifold. I re-tightened that bolt after replacing the O2 sensor. It was kind of hard to tell if the joint was seal good or not? Any tips to confirm this.

 

You will hear a repeating noise like a "pssst" if it's not sealed

 

Tightened the bolt and noise went away. Thanks.