Idle Hc/Co Concentration Check Method - Toyota 4-Runner 1985 Repair Manual

EM-10 ENGINE MECHANICAL -
Idle HC/CO Concentration Check Method
IDLE HC/CO CONCENTRATION CHECK METHOD
NOTE: This check method is used only to
determine whether or not the idle HC/CO com-
plies with regulations.
PRECHECK
INITIAL CONDITIONS
(a) Normal engine operating temperature
(b) Choke fully open (with carburetor)
(c) Air cleaner installed
(d) All pipe and hoses of air intake system
connected (with EFI)
(e) All accessories switched off
(f) All vacuum lines properly connected
(g) EFI system wiring connectors fully
plugged.
(h) Idle speed set correctly
TROUBLESHOOTING
HC CO Problems
High Normal Rough idle
High Low Rough idle
Fluctuating HC reading
High High Rough idle
Black smoke from exhaust
(i)
Carburetor fuel level about even with
~.
correct level in the sight glass
(j) Tachometer and HC/CO meter calibrated
and at hand
MEASUREMENT
1 . INSERT TESTING PROBE OF HC/CO METER
INTO TAILPIPE AT LEAST 40
em
(1.3
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 regulation, see the table below for possi-
ble causes.
Causes
1. Faulty ignition:
• Incorrect timing
• Fouled, shorted or improperly gapped plugs
• Open or crossed ignition wires
• Cracked distributor cap
2. Incorrect valve clearance
3. Leaky EGR valve
4. Leaky exhaust valves
5. Leaky cylinder
1. Vacuum leak:
• Vacuum hose
• Intake manifold
• Air chamber (with EFI)
• PCV line
• Carburetor base (with carburetor)
• Throttle body (with EFI)
• CMH (with carburetor)
2. Leaky MC valve (with carburetor)
1. Restricted air filter
2. Plugged PCV valve
3. AS system problem (with carburetor)
4. Faulty carburetion: (with carburetor)
• Faulty choke action
• Incorrect float setting
• Leaking needle or seat
• Leaking power valve
5. Faulty EFI system: (with EFI)
• Faulty pressure regulator
• Clogged fuel return line
• Faulty air flow meter
• Defective water thermo sensor
• Defective air thermo sensor
• Faulty EFI computer
• Faulty injector
• Faulty cold start injector