The car runs smoothly, starts immediately, gets 20-22 mpg around town, doesn’t smoke or use oil. It flunked a smog test because the spark advance is at 25 Degrees not 5 Degrees. How is the #of degrees advance really a smog problem when all of the other indicators show an efficient fuel use vehicle?
What part of the smog test did the vehicle fail?
Tester
My '87 passes easily. I don’t know that they’ve ever tested my spark advance.
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Did it fall, then they checked the timing? Could be the distributor advance mechanism (vacuum and or centrifugal) is frozen, and the timing has been set to compensate.
What exactly is on the paperwork from the test?
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Did you thoroughly warm up the vehicle? Many tests fail when the car is running cold.
It’s been many years but I believe that overly advanced timing causes NOx problems. And it also causes cracked pistons and broken starters.
The truck failed the visual inspection, the ignition timing is off.
Warming up the vehicle or engine will have no affect on the visual inspection, the ignition timing must be within specifications.
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He must be in CA. He failed the part of the test where they inspect to see if the idle speed and ignition timing are set to manufacturer specs.
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You have to get the timing set right and get back to the test. Test the vacuum advance with a vacuum tester; the cheap plastic one. You could have a mechanic do it.
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Great thought @pleasedodgevan2. The entire problem could be an improper vacuum connection. If that’s the cause @RobertB.Gray, your truck will have a really bad hesitation and loss or power until you get to cruising speed.