FiveSeventyZee Posted February 8, 2010 Share Posted February 8, 2010 I got my truck smog tested today, its a 1980 720 4x4. I know it's not a z but I have gotten help on my z from this site so I'm sticking to it. Anyways, I got a high count on HC, I passed, but barely. The measures were: HC meas: 209/127, max: 211/128 CO meas: 0.09/0.09, max: 1.53/1.33 NO meas: 277/241, max:1507/1367 My car does idle high, I'm not sure what these numbers suggest. Any ideas? Quote Link to comment Share on other sites More sharing options...
pat1 Posted February 8, 2010 Share Posted February 8, 2010 hc is unburnt fuel, your running a bit rich. Lean that carb out a bit. Quote Link to comment Share on other sites More sharing options...
FiveSeventyZee Posted February 8, 2010 Author Share Posted February 8, 2010 ok, I'll give that a try next time I get a chance. I've got school tomorrow so we'll see. Thank you Quote Link to comment Share on other sites More sharing options...
Apex944 Posted February 8, 2010 Share Posted February 8, 2010 Definately running rich, you can tell by how low the NOx reading is. The extra fuel is cooling off the cylinder creating less NOx which is good for less NOx but bad because your wasting alot of fuel. Leaning out the carb/carb's should clean it up. Quote Link to comment Share on other sites More sharing options...
FiveSeventyZee Posted February 8, 2010 Author Share Posted February 8, 2010 ok. I'll definitely lean out my mixture. how can I tell if it's better though? I'm not re smogging it for a while so I won't know. will it run smoother? Quote Link to comment Share on other sites More sharing options...
Dtsnlvrs Posted February 8, 2010 Share Posted February 8, 2010 DONT DO ANYTHING TO THE CARBS...check your ignition timing first...chances are it is advanced too far. Always set the ignition timing to the stock setting prior to running a smog check....an over advanced ignition will cause the HC levels to be too high Quote Link to comment Share on other sites More sharing options...
Apex944 Posted February 8, 2010 Share Posted February 8, 2010 Good call Dtsnlvrs, definately check your ignition timing before tweaking on your carb. Overly retarded ignition timing can cause high HC and CO as well. I haven't had do do any hard thinking on 5 gas readings in over a year, should pull out my books and read over it all again The only way you can tell if it's improved is if you run it on a 5 gas machine (smog test) again and see if it improved. Quote Link to comment Share on other sites More sharing options...
pat1 Posted February 8, 2010 Share Posted February 8, 2010 DONT DO ANYTHING TO THE CARBS...check your ignition timing first...chances are it is advanced too far. Always set the ignition timing to the stock setting prior to running a smog check....an over advanced ignition will cause the HC levels to be too high The timing to far advanced will cause the nox to be High. It will be hight because when you advance timing the cylinder temp goes up. It's a good idea to check the timing though. Quote Link to comment Share on other sites More sharing options...
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