Toyota 3S-GE Repair Manual page 58

E644 ENGINE - ENGINE MECHANICAL
Troubleshooting
If the CO/HC concentration does not comply with
regulations, perform troubleshooting in the order
given below.
(a) Check oxygen sensor operation.
(See page EG—286)
5- (b) See the table below for possible causes, and then
inspect and correct the applicable causes if neces-
sary.
HC CO Problems Causes
High Normal Rough idle 1. Faulty ignitions:
0 Incorrect timing
e Fouled, shorted or improperly gapped plugs
0 Open or crossed high—tension cords
0 Cracked distributor cap
2. Incorrect valve clearance
3. Leaky intake and exhaust valves
4. Leaky cylinder
High Low Rough idle 1. Vacuum leaks:
(Fluctuating HC reading) 0 PCV hose
0 Intake manifold
0 Throttle body
0 ISC valve
0 Brake booster line
2. Lean mixture causing misfire
High High Rough idle 1. Restricted air filter
(Black smoke from exhaust) 2. Faulty EFI systems:
0 Faulty pressure regulator
0 Clogged fuel return line
0 Defective water temp. sensor
e Faulty ECU
0 Faulty injector
0 Faulty throttle position sensor
0 Faulty vacuum sensor
VO5444