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PGM-FI System
Random Misfire
1T0-500
1 a nd Fo-30ittrrousFF0304-l
ThB scan tool indicates Diagnostic Trouble Code {DTC) P0300 and some of
P0301 - P0304: Random misfire.
Doscription
Misfir; detection is accomplished by monitoring the crankshaft speed with the crankshaft speed fluciuation
sensor which
is attached to the crankshsft.
lf misfiring strong enough to damage the catalyst is detected, the MIL will blink during iho time of its occurrence, and
DTC
p0300 and some of DTCS p0301 through P0304 will be stor€d. Then, after misfire has ceased, the MIL will come on.
lf misfiring that increases emissions is detected during two consecutive driving cycles, the MIL will come on, and
DTC
PO3O0 and some ot DTCS P0301 through P0304 will be stored
NOTE: lJ some of the DTCS listed below are stored at the same time as a misfire DTC, troubleshoot those DTCS
first. then
troubleshoot the misfire DTC.
P0171, P0172: Fuel metering
P0505: ldle Control SYstem
P1361, P1362: TDC sensor
P1381. P1382: CYP sensor
P1508: IAC valve
Possible Cause
. Fuel pump insufficient fuel pressure. amount of flow
.
Fuel line clogging, blockage, leakage
. Fuel {ilter clogging
a Fuel pressure regulator stuck open
.
Distributormallunction
o lgnition coil wire open, leakage
. lgnition control module malfunction
. Valves carbon deposit
a Compression low
.
IAC valve malfunction
.
Fast idle thermo valve malfunction
o Fuel does not meet Owner's Manual spec., lackotfu€l
. VTEC system malfunction
Troubleshooting
By test-driving, determine the conditions during which misfire occurs. Depending on these conditions, test in the order
described in the table below.
Fuel
pressure
Distributor
and lgnition
wires
tcM
IAC Valve
Valve
Clearance
wEc
System
11 1 1 8
section 23
section 23
1 1- 100
section 6
section 6
Only low rpm and
loao
@
o
@
@
Only accelerating
o
@
o
Only high rpm and
load
o
@
@
@
o
Not specification
o
@
@
@
@
NOTE: lf misfire doesn't recur, some possible causes arefuel that doesn't meet owner's manual spec, lackoffuel, carbon
deposits on spark plug, etc.
1 1 - 7 8
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Troubleshooting
