1991 Toyota Tercel Failed smog

JOHNCHI

MEMBER
1991 TOYOTA TERCEL
4 CYL
FWD
MANUAL
18,303 MILES

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:(

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

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.