1983 Toyota Tercel

NOTE: This check is used only to determine whether or not the idle HC/CO complies with the state or city regulations.
PRECHECK
Initial conditions

• Normal engine operating temperature
• Choke fully open
• Air cleaner installed
• All accessories switched off
• All vacuum lines properly connected
  NOTE: All vacuum hoses for EGR systems, etc. should be properly connected.
• Ignition timing set correctly
• Transmission in N range
• Carburetor float level even with the correct level in the slight glass
• Tachometer and HC/CO meter at hand and calibrated

1. INSERT TESTING PROBE OF HC/CO METER INTO TAILPIPE AT LEAST 60 cm (2 ft.)
2. MEASURE HC/CO CONCENTRATION AT IDLE
   Wait at least one minute before measuring to allow the concentration to stabilize.
   Complete the measuring within three minutes.
   If the HC/CO concentration does not conform to regulations, see the table below for possible causes.

HC	CO	Problems	Causes
High	Normal	Rough idle	Faulty ignition: Incorrect timing Fouled, shorted or improperly gapped plugs Open or crossed ignition wires Cracked distributor cap Incorrect valve clearance Leaky EGR valve Leaky exhaust valves Leaky cylinder
High	Low	Rough idle Fluctuating HC reading	Vacuum leak: Vacuum hose Intake manifold PCV line Carburetor base
High	High	Rough idle Black smoke from exhaust	Restricted air filter Plugged PCV valve AS system problem Faulty carburetor: Faulty choke action Incorrect float setting Leaking needle or seat

NOTE: If the HC/CO concentration cannot be corrected in accordance with this troubleshooting table, adjust the idle mixture.