1991 Toyota Tercel Failed smog

1991 TOYOTA TERCEL
18,303 MILES • 4 CYL • FWD • MANUAL
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JOHNCHI
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failed the 15 mph HC(PPM):
rpms=1630
CO2%=14.10
O2%=0.55
HC(PPM)=156 Avg. is 31 Max. is 142


after failing i purchased new plugs because the old ones were really rounded off..... so i was curious to see what trouble codes would show up on the diagnostics...it gave me a code 42 ( Vehicle Speed Sensor Signal ) trouble area says....

VEHICLE SPEED SENSOR CIRCUIT
VEHICLE SPEED SENSOR; ECU...???WHAT DO YOU RECOMMEND??? i have 3 days to fix the problem??
any suggestions?? oh i forgot to tell you the speedometer cable is broken..is that why, I didnt pass the smog test...point me in the right direction please..........:(
Oct 28, 2009 at 4:03 AM
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RASMATAZ
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Fix the speedo cable might just take care of the VSS code.

HC problems could mean unburned gasoline is passing through the engine and entering the exhaust. The three most common causes include ignition misfire, lean misfire and low compression (typically a burned exhaust valve). Ignition misfire can be caused by worn or fouled spark plugs, bad plug wires or a weak coil. Lean misfire results where there is too much air and not enough fuel, so check for vacuum leaks, dirty injectors or a fuel delivery problem. In addition to these, hydrocarbon failures can also be caused by oil burning due to worn valve guides, valve guide seals and/or rings.
Oct 28, 2009 at 4:38 AM