Isuzu 4JH1 - Diagnosis

TROUBLESHOOTING 6 – 5
2. Unstable Idling
Step Action Value(s) Yes No
1 Was the fuel line air bled completely? — Go to Step 3 Bleed the air
2 Was the fuel line leakage or blockage found? — Repair or
replace relation
parts. Go to Step 4
3 Was the water contained in the fuel? — Replace the
fuel Go to Step 5
4 Was the fuel filter element clogged? — Replace the
fuel filter
element Go to Step 6
5 Was the injection starting pressure or the injection
spray condition OK?
(See below)
Go to Step 7
Replace the
injection nozzle
6 Was the injection nozzle sticking? See Step 6 Replace the
injection nozzle Go to Step 8
7 Check the throttle valve condition.
Was the idling port clogged in the throttle valve?
— Repair or
replace the
throttle valve Go to Step 9
8 Was the valve clearance improper adjusted? 0.4 mm
(0.016 in)
both intake
and exhaust
valves
Adjust the
valve clearance Go to Step 10
9 Was the compression pressure OK? 3.0MPa (31.0
kg/cm
2
, 441
psi) at
200rpm
Go to Step 11
Readjust the
valve clearance
or replace the
cylinder head
gasket or
cylinder liner or
piston or piston
ring or valve
and valve seat
10 Are any DTC stored? — Go to indicated
DTC Solved
Injection nozzle opening pressure
1st = 19.5 MPa (199 kg/cm
2
, 2828 psi)