Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - View Single Post - Hydrocarbon emissions too high need help tried everything.

94_240sx · 08-22-2006, 03:07 PM

I have base model 95 MX-3 which is a daily driver and had exact same problem last week. At 15mph, 141 is max in Texas. I had 199. Did full tune up since it was due anyway. New plugs, wires, rotor, cap, timing belt, water pump, trans mount, engine mounts. intake tube(cracked), oil change whole nine yard. It went down to 152. Still couldn't pass. My car was running slightly rich. So adjusted the timing and we heard knocking noise, so put it back the way it was. Finally, installed new cat and guess what? I got 11. In your case, adjust the timing. I think it'll fix it. BTW, intake cleaning with Seafoam should help too. I'm not sure if this is true or not, but someone said adding alcohol or water will clean up O2 sensor and decrease HC reading little bit... People say MX-3 O2 sensor should last forever, so I didn't bother to replace it.

08-22-2006, 03:07 PM	#9
94_240sx Zilvia Addict Join Date: Aug 2006 Location: TX Posts: 686 Trader Rating: (7)	Similar experience I have base model 95 MX-3 which is a daily driver and had exact same problem last week. At 15mph, 141 is max in Texas. I had 199. Did full tune up since it was due anyway. New plugs, wires, rotor, cap, timing belt, water pump, trans mount, engine mounts. intake tube(cracked), oil change whole nine yard. It went down to 152. Still couldn't pass. My car was running slightly rich. So adjusted the timing and we heard knocking noise, so put it back the way it was. Finally, installed new cat and guess what? I got 11. In your case, adjust the timing. I think it'll fix it. BTW, intake cleaning with Seafoam should help too. I'm not sure if this is true or not, but someone said adding alcohol or water will clean up O2 sensor and decrease HC reading little bit... People say MX-3 O2 sensor should last forever, so I didn't bother to replace it.