6-12
ENGINE DIAGNOSIS
Condition
Possible Cause
Reference Item
Engine hesitates
(Momentary lack of
response as the
accelerator is
depressed.
Can occur at
all
vehicle speeds.
Usually most severe
when first trying to
make the vehicle
move, as from a
stop sign.)
Ignition system out of order.
D
Spark plug faulty or plug gap as out
of adjustment
Fuel system out of order.
D
Fuel pressure out of specification
– Clogged fuel filter
– Faulty fuel pressure regulator
D
Clogged fuel filter, hose or pipe
Engine overheating
Engine and emission control system out
of order.
D
Faulty injector
D
Faulty TP sensor, ECT sensor or MAP
sensor
D
Faulty ECM .
Low compression
Spark plugs in Section 6F.
Diag. Flow Table B-3 in Section 6E1.
Fuel pressure check in Section 6E1.
Refer to “Overheating” Section.
Fuel injector in Section 6E1.
TP sensor, ECT sensor or MAP
sensor in Section 6E1.
Inspection of ECM and its circuit in
Section 6E1.
Previously outlined.
Surges
(Engine power variation
under steady
throttle or cruise.
Feels like the vehicle
speeds up and down
with no change in
the accelerator
pedal.)
Ignition system out of order.
D
Defective spark plug (excess carbon
deposits, improper gap, and burned
electrodes, etc.)
Fuel system out of order.
D
Variable fuel pressure
– Clogged fuel filter
– Kinky or damaged fuel hose and line
– Faulty fuel pressure regulator
Engine and emission control system out
of order.
D
Faulty MAP sensor
D
Faulty injector
D
Faulty ECM
Spark plugs in Section 6F.
Diag. Flow Table B-3 in Section 6E1.
MAP sensor in Section 6E1.
Fuel injector in Section 6E1.
Inspection of ECM and its circuit in
Section 6E1.