My car has passed emissions every year except this one. It has now failed 5 times. The problem is with hydrocarbons at idle & loaded. I have replaced the distributor cap & rotor, plug wires, plugs, & retarded the timing, which brought the readings way down - but still over the limit. The fuel plugs on the bottom of my quadrajet have been sealed with JB Weld. I am within 25 & 43 on each reading respectively, but the CO has jumped up too much for my liking, so I am leery of retarding the timing any more. The setup I am running is as follows: 350, stock heads, custom grind cam with about 475 lift (113 degrees separation on the lobes), Weiand intake, headers/duals, quadrajet carb, HEI w/ an MSD 6, & a Flamethrower coil. The ignition setup is about 2 years old & the engine only has about 30,000 miles on it. I get steady pulses of light when I check each individual plug wire with a timing light. I am wondering if maybe the coil is breaking down & throwing a much weaker spark. Since the MSD box throws multiple sparks below 3,000 RPM & the entire emissions test is done below that RPM level, I can't figure out why there would be unburned fuel. The exhaust pulse is as strong as it ever was, so I would not be inclined to think that there is a compression problem. I have checked all the vacuum hoses & also the intake/carb for leaks & found none. The alternator puts out 14.6 volts at idle, so the electrical end is covered as well. Any ideas? I guess it's time to get our bass ackwards Arizona legislature to exempt all cars when they turn 25 years old.
1971-Chevelle
Anythings possible especially with electrical equipment. Anything that has electricity going through it especially wires tend to break down over time and build up resistance. Are you getting a nice hot spark at idle or is it more of a orange color? A good spark should be a whitish/bluish color.
I had one that would not pass and I disconnected the modulator valve so it would stay in 1st gear without going to full throttle. With the RPM's up high enough it passed with flying colors. Of course with a 2.41 gear it did not rev too high. This was my 77 Buick Regal with a Chevy 350 installed. The guy that was testing the car said the car must be geared really low. 
I told him it had a 4.56 in it.
You might want run the timing farther back if possible just for the test. If car is running at 195 or better it will pass easier as well. Changing the oil will make it easier I have heard too, less gas in the oil. Hope this might have helped some.
I told him it had a 4.56 in it. You might want run the timing farther back if possible just for the test. If car is running at 195 or better it will pass easier as well. Changing the oil will make it easier I have heard too, less gas in the oil. Hope this might have helped some.
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