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I have a 95 Isuzu Rodeo with 3.2. the HC readings are 63 @15mph & 44@ 25mph. I did an oil change, replaced the plugs, wires, 02 sensor, and put in different fuel additives with each gas fill-up.
I noticed an increase in fuel economy. This was the fourth check for this go-around. Incidently I replaced the cat & O2 sensor the last smog 2yrs ago. I want to throw in the towel but I got a ton invested now. Please help.
Check for a leak in your exhaust before the 02 sensors. If air is getting in this can make the O2 sensor see a weak mixture which will cause the ECU to make he mixture rich.
I had a similar issue on my daughter's car which turned out to be a cracked exhaust manifold - http://www.handyhowie.co.uk/handyhowie/Colt_Exhaust_Leak.html
