My 78 Trail Duster just failed the stringent CA smog test.
The truck is all factory correct with 94,000 miles. It is a Federal emissions truck with a GVWR of 6100 lbs. 440, thermoquad, dual exhaust and a 727. Because of the Full Time 4wd, the test consists of a standard sniffer test at idle and at 2500 rpms. The first test it ran well UNDER the allowable limits of HCs at 2500. 360 allowable with 36 showing. At idle it went waaaay over, 600 when 300 was allowable. The tech thought that there could be a vacuum leak or two, so I replaced 2 vac lines and the carb base gasket. I went back, and now it is actually worse! The idle #s went to 1003 and the 2500 rpm test was at 50. What the heck?
My experience with smog guys seems to be bad. Whenever I have had a problem, they say..."Uhh, it could be an oxygen sensor"...OR "Ahhh, maybe it is a vacuum leak, or a fouled plug, or a ficklesnort spring." EASY for them to just throw my money around with no regard for my wallet. Are these guys actually trained or do they just guess all of the time?
This engine runs smoothe and has no smoke. No unusual odors coming from the exhaust. It has new plugs and oil. It is no hot rod, but it runs well. Would aged plug wires cause a fail at idle but still allow an engine to run so clean at higher rpms? I'm interested in any pointers on what I can do to get this thing to pass. Would a pair of catalytic converters make any differnce in the HC numbers? Any other ideas that I can try?
Thanks, Greg