Mechanics

I HAVE A 01 WITH PO300 AND PO307 CODES I HAVE CHANGED PLUGS AND PLUG WIRES IT IS STILL MISSFIRING PLEASE HELP

2001 Chevrolet Camaro • 123,000 miles

Missfiring at idle light stumble upon acceleration in higher gears
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Joey robinson
January 3, 2012.




What engine?
ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 5.7L -2001 Chevrolet Camaro
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DTC P0300: ENGINE MISFIRE DETECTED

NOTE: For circuit reference, see WIRING DIAGRAMS article.
Description

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Tip: DTC P0300
Crankshaft Position (CKP) sensor reluctor (4X) is located on side of engine block behind starter assembly. CKP sensor will send a pulse on every falling edge of 4X reluctor wheel. A misfire will cause
a change in crankshaft speed. Powertrain Control Module (PCM) times interval between each pulse and compares each new interval with previous one to determine when an excessive change in crankshaft
speed has occurred. A certain amount of acceleration/deceleration is expected between each firing stroke, but if crankshaft speed changes are more than expected amount, PCM will interpret this as a
misfire. PCM continuously calculates crankshaft position from low and high resolution signals. This information is used to determine which cylinder is misfiring so that PCM can increment appropriate
misfire counter.
Code Enable Criteria

For DTC to run, the following conditions must be met: ? DTCs P0101, P0102, P0103, P0117, P0118, P0121, P0122, P0123, P0125, P0335, P0336, P0341, P0342, P0343, P0500, P0502, P0503, and P1258 are not set.
? Engine speed is 450-3001 RPM. ? Ignition voltage is 10-18 volts.
? Engine coolant temperature is 19-266°F (-7 to 130°C). ? Fuel level is more than 10 percent.
? Throttle Position (TP) sensor angle is steady within 1 percent. ? ABS system and the Traction Control system are not active.
? Transmission is not changing gears.
? AIR diagnostic test is not in progress. ? A/C clutch is not changing states.
? PCM is not in fuel shutoff mode or decel fuel cut-off mode. ? ABS signals not exceeding rough road thresholds.
DTC will set when PCM determines an emissions-type misfire and/or a catalyst-damaging misfire is present.
Diagnostic Procedures

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ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 5.7L -2001 Chevrolet Camaro
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1.
If powertrain diagnostic system check was performed, go to next step. If powertrain diagnostic system check was not performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK
under DIAGNOSTIC SYSTEM TESTS. After performing powertrain diagnostic system check, go to next step.
CAUTION: Before performing this diagnostic test, CKP system variation
learn procedure must be completed. See CRANKSHAFT POSITION SENSOR VARIATION LEARN PROCEDURE under
PROGRAMMING.
NOTE: Ensure ABS and traction control system are operating properly
before beginning this diagnostic test. If any DTCs other than P0135 and P0155 are set, repair those DTCs first. See DIAGNOSTIC
TROUBLE CODE DEFINITIONS.
2.
Start and operate engine at idle. Using scan tool, select MISFIRE DATA LIST function and monitor MISFIRE CUR. COUNTERS (one counter per cylinder). If any misfire counter is
incrementing, go to step 4. If misfire counter is not incrementing, go to next step.
Turn ignition on, engine off. Review FREEZE FRAME and/or FAILURE RECORDS data for this DTC and observe parameters. Turn ignition off for at least 30 seconds. Start engine. Operate
vehicle within conditions required to set this DTC. Using scan tool select DTC option and SPECIFIC DTC option, then enter this DTC. If scan tool indicates that this DTC failed this
ignition, go to next step. If scan tool does not indicate that this DTC failed this ignition, see DIAGNOSTIC AIDS.
If only one cylinder is misfiring, go to step 6 next step.
Check if any of the following conditions exist: ? Using scan tool, check HO2S readings. If signal is fixed less than 200 mV go to DTC P0131: HO2S CIRCUIT VOLTAGE LOW - BANK 1, SENSOR 1; DTC P0151: HO2S
CIRCUIT LOW VOLTAGE DTC P0151: HO2S CIRCUIT LOW VOLTAGE - BANK 2, SENSOR 1. If signal is fixed greater than 900 mV go to DTC P0132: HO2S CIRCUIT
VOLTAGE HIGH - BANK 1, SENSOR 1; P0152: HO2S CIRCUIT HIGH VOLTAGE P0152: HO2S CIRCUIT HIGH VOLTAGE - BANK 2, SENSOR 1.
? Check that accessory drive pulleys are not misaligned.
? Check vacuum hoses for splits, kinks and proper routing. See Fig. 13.
? Check for leaks at throttle body, intake manifold, EGR valve or PCV system. ? Check PCM grounds for proper connection.
? Check that all injector harness connectors are connected to proper injector/cylinder. Check for blown INJ fuses.
? Test fuel pressure. See appropriate BASIC DIAGNOSTIC PROCEDURES article. ? Check for restricted exhaust system.
? Check for fuel contamination.
3.
4.
. If more than one of cylinders is misfiring, go to
5.
If any conditions are present, repair as necessary. After repairs, go to step 17. If conditions are not present and repair is not necessary, go to next step.

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ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 5.7L -2001 Chevrolet Camaro
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6.
Turn ignition off. Disconnect suspect injector connector corresponding to misfire counter that was incrementing. Connect Injector Test Light (J-34730-2C) to connector of suspect injector. Start
engine. If injector test light if flashing, go to next step. If injector test light is not flashing, go to DTC P0200: INJECTOR CONTROL CIRCUIT.
Turn ignition off. Reconnect suspect injector connector. Disconnect suspect ignition wire to spark plug that corresponds to misfire current counter that was incrementing. Install Spark Plug Tester
(J-26792) to spark plug wire. Start engine. If spark is present at spark plug tester, go to step 9. If spark is not present, go to next step.
Disconnect suspect ignition wire from ignition coil. Using DVOM, measure resistance of suspect spark plug wire. If resistance is less than 700 ohms, replace ignition wire. If resistance is not less
than 700 ohms, go to step 16.
Remove and check spark plug from suspect cylinder. If spark plug is okay, go to next step. If spark plug is faulty, go to step 11.
Swap spark plug to another cylinder that is operating properly. Operate vehicle under same conditions that misfire occurred. If misfire moved with spark plug, go to step 15. If misfire is still
present at original cylinder, perform fuel injector coil test. See appropriate SYSTEM & COMPONENT TESTING article. If injector coil test does not isolate condition, diagnose engine
mechanical condition and repair as necessary.
If spark plug is fouled with oil or coolant, diagnose mechanical engine problem and repair as necessary. If spark plug is not fouled with oil or coolant, go to next step.
Check if spark plug is fouled with gasoline. If spark plug is not gasoline fouled, go to next step. If spark plug is gasoline fouled, diagnose fuel system. See appropriate SYSTEM & COMPONENT
TESTING article. If fuel system diagnosis does not isolate condition, diagnose engine mechanical condition and repair as necessary.
Check spark plug for signs of cracks, wear or improper gap. If spark plug is faulty, go to next step. If spark plug is okay, perform fuel injector coil test. See appropriate SYSTEM & COMPONENT
TESTING article. If injector coil test does not isolate condition, diagnose engine mechanical condition and repair as necessary.
Replace or re-gap spark plug. After replacing or re-gapping spark plug, go to step 17
15. Replace faulty spark plug(s). After replacing spark plug(s), go to step 17.
16. 17.
7.
8.
9.
10.
11.
12.
13.
.
14.
Replace faulty spark plug wire. After replacing spark plug wire, go to next step.
If complaint is due to MIL flashing, perform DTC P0420: CATALYST SYSTEM LOW EFFICIENCY - BANK 1; P0430: CATALYST SYSTEM LOW EFFICIENCY - BANK 2. If
MIL is not flashing, go to next step.
Using scan tool, clear DTCs. Turn ignition off for at least 30 seconds. Start engine and allow it to reach normal operating temperature. Operate vehicle within conditions for setting this DTC. If
scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step 2.
19. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS.
If no undiagnosed DTCs are displayed, system is okay.
18.
Diagnostic Aids

If vehicle is ran out of fuel, misfire DTC will set possibly along with DTC P0461. Check for restricted fuel filter. Misfire may not be detectable at idle. Road test vehicle and monitor misfire counters for

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ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 5.7L -2001 Chevrolet Camaro
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misfire condition under load. Misfire DTC may also be set by excessive vibrations from warped brake rotors, drive shaft out of balance or certain road conditions.
If more than one cylinder is misfiring, only one cylinder may be displayed on misfire counter. After first cylinder is repaired, additional cylinders will display. If ignition coil or module ground circuit is open
for one side of engine, scan tool may only display 2 or 3 cylinders misfiring for that bank. Check and repair ground connections for that bank of cylinders.
If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.
Fig. 13: Identifying Underhood Vacuum Hoses Courtesy of GENERAL MOTORS CORP.

Rivermikerat
Jan 4, 2012.


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