innerware Posted October 1, 2003 Share Posted October 1, 2003 What causes a car to have too high a CO level when trying to pass smog? I have a 78 280z that is now a gross polluter. I failed my CO test by about double. Everything is bassically stock. Any ideas are good. I am bringing it to my shop Friday anyway but I don't trust even the most trusted shop, and I trust my shop. Just thought I would get some input. Thanks as always, Kyle Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted October 1, 2003 Share Posted October 1, 2003 I sent you a reply to your email, but I will post the infos here too for others... Basically; HC come from buildup and carbon deposits CO comes from incomplete burn. (There are other factors such as EGR that come into play under higher levels of test failure) To remedy CO, get new spark plugs, new air cleaner, and possibly new CAT. Any muffler shop should be able to temp check a CAT before, at, and after the CAT to see how well it is working. Run the car down the highway at a nice high, maintainable RPM to get it nice and warm to burn stuff completely and then take it in for your test. As a note, to anyone who needs to remedy HC, make sure you are not running too rich, get new plugs, air cleaner, and make sure your exhaust is flowing good. Run fuel system cleaners for a couple weeks religiously and try testing again after a hot highway run. BTW, in any case, changing your fuel mixture to lean before the test also is a nice way to "cheat" Quote Link to comment Share on other sites More sharing options...
Guest bluex_v1 Posted October 1, 2003 Share Posted October 1, 2003 ...and as for NOx emissions, make sure you aren't too lean, because NOx emissions will result from higher than normal combustion temps. Carbon deposits can lead to their increase as well. -- This is where EGR is employed if you have it. Quote Link to comment Share on other sites More sharing options...
buzzsawbaby Posted June 18, 2009 Share Posted June 18, 2009 I have a similar problem but my levels are a lot higher. The first test failed with new plugs, coil, leads. I replaced the cat and I was getting 351 HC and 8.20 (limit is 214 and 1.36). After changing the oil I got the HC down to 150ish but the CO is still up there at about 6. Any ideas? Quote Link to comment Share on other sites More sharing options...
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