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Tim's Auto Repair
Tim's Auto Repair, Mechanic
Category: Car
Satisfied Customers: 12744
Experience:  Have owned a repair shop for 25 yrs.
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Isuzu Rodeo: Hi , I still have p0300 did coil packs, coil

Customer Question

Hi ,
I still have p0300
did coil packs, coil boots, and plugs. sprayed either all over motor, no signs of leak. what next?
Submitted: 1 year ago.
Category: Car
Expert:  Tim's Auto Repair replied 1 year ago.

tims auto repair :

ok

tims auto repair :

you still get the 300 code?...does the engine run any better at all?

Customer:

yes. motor runs great, but when the check engine light comes on and blinks it runs rich.

Customer:

it smells rich and sluggish.

tims auto repair :

and,,still gives only the 300 code after you clear it?

Customer:

every time reset light runs great, until light comes on.

Customer:

yep

tims auto repair :

ok

tims auto repair :

clean the maf sensor with maf or carb cleaner

tims auto repair :

sometimes these will do this

tims auto repair :

stand buy,,

tims auto repair :

i will give you tests and checks you can do for this 300 code

Customer:

great, i have to go buy another can.

Customer:

okay

tims auto repair :

note: sometimes when the engine light flashes like this,,it is a clogged catalyst converter

tims auto repair :

stand by

Customer:

well, one cat was replaced

tims auto repair :

i see

tims auto repair :

hmmm

tims auto repair :

with an aftermarket?

Customer:

and when the exhaust person put his pressure gauge on it read little back pressure

Customer:

yes

Customer:

after market

tims auto repair :

you may want to have that checked again

tims auto repair :

P0300.........
















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Steps 1 - 4










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Steps 5 - 8










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Steps 9 - 14










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Steps 15 - 18










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Steps 19 - 20



DTC P0300 Engine Misfire Detected

DTC P0300 Engine Misfire Detected Circuit Description
The powertrain control module (PCM) is able to detect a misfire by monitoring the 58X reference and the camshaft position input signals. If the PCM detects crankshaft speed variations that indicate 1% or more of cylinder firing events are misfires, the PCM will disable the torque converter clutch (TCC). If the RPM variation detected indicate a true misfire condition, DTC P0300 will be set.

Conditions for Setting the DTC
- None of the following DTCs occur: TP sensor, MAF sensor, CMP sensor, VSS, ECT sensor, ABS Rough Road sensor, CKP sensor.
- The engine speed is between 600 and 6250 RPM.
- The system voltage is between 11 and 16 volts.
- The engine temperature sensor (ECT) indicates an engine temperature between -7 °C (20 °F) and 120 °C (248 °F).
- Throttle angle is steady and throttle changes less than 3% per 125 milliseconds.
- The PCM detects a crankshaft RPM variation indicating a misfire that is sufficient to cause catalytic converter damage or emissions levels to exceed the mandated standard.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) the first time the fault is detected.
- If the misfire is severe enough to cause possible catalyst damage, the PCM will flash the MIL for as long as the misfire remains at catalyst damaging levels.
- The PCM will disable the TCC operation.
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle in which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0300 will clear after 40 consecutive warm-up cycles occur without a fault.
- DTC P0300 can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids
The scan tool display Misfire Cur. #1 through #6 can be useful to determine whether the misfire is isolated to a single cylinder.
- Damaged or faulty ignition coil - Check for cracks or other damage.
- Substitute a known good coil - Swap the ignition coils and retest. If the misfire follows the coil, replace the ignition coil.
If the misfire is random, check for the following conditions:
- System grounds - Ensure all connections are clean and properly tightened.
- MAF - A mass air flow (MAF) sensor output that causes the PCM to sense a lower than normal air flow will cause a lean condition.
- Air induction system - Air leaks into the induction system which bypass the MAF sensor will cause a lean condition. Check for disconnected or damaged vacuum hoses, incorrectly installed or faulty PCV valve, or for vacuum leaks at the throttle body, EGR valve, and intake manifold mounting surfaces.
- Fuel pressure - Perform a fuel system pressure test. A faulty fuel pump, plugged filter, or faulty fuel system pressure regulator will contribute to a lean condition.
- Injector(s) - Perform an injector coil/balance test to locate faulty injector(s) contributing to a lean or flooding condition. In addition to the above test, check the condition of the injector O-ring.
- EGR - Check for a leaking valve, adapter, or feed pipes which will contribute to a lean condition or excessive EGR flow.
- Fuel quality - Using fuel with the wrong octane rating for the vehicle may cause driveability problems.
Although alcohol-enhanced fuels may raise the octane rating, the fuel's ability to turn into vapor in cold temperatures deteriorates. This may affect the cold driveability of the engine. The Reid Vapor Pressure of the fuel can also create problems in the fuel system, especially during the spring and fall when changes by the refineries may not coincide with changes in the weather.
- Vehicle marshalling - The transportation of new vehicles from the assembly plant to the dealership can involve as many as 60 key cycles within 2 to 3 miles of driving. This type of operation contributes to the fuel fouling of the spark plugs and will turn on the MIL with a P0300 Misfire DTC.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Customer:

Perform an injector coil/balance test to locate faulty injector(s) contributing to a lean or flooding condition. In addition to the above test, check the condition of the injector O-ring

Customer:

how do i do this?

tims auto repair :

one moment

tims auto repair :

 
















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Fuel Injector Coil Test Procedure and Fuel Injector Balance Test Procedure










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Steps 1 - 2










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Step 9










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Steps 10 - 11



Fuel Injector Coil Test Procedure and Fuel Injector Balance Test Procedure








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Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:

2. Relieve the fuel pressure by connecting the J 34730-1 Fuel Pressure Gauge to the fuel pressure connection on the fuel rail.

CAUTION: In order to reduce the risk of fire and personal injury, wrap a shop towel around the fuel pressure connection. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gauge. Place the towel in an approved container when the connection of the fuel pressure gauge is complete.

Place the fuel pressure gauge bleed hose in an approved gasoline container. With the ignition switch OFF, open the valve on the fuel pressure gauge.








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3. Record the lowest voltage displayed by the DVM after the first second of the test. (During the first second, voltage displayed by the DVM may be inaccurate due to the initial current surge.)


- The voltage displayed by the DVM should be within the specified range.
- The voltage displayed by the DVM may increase throughout the test as the fuel injector windings warm and the resistance of the fuel injector windings changes.
- An erratic voltage reading (large fluctuations in voltage that do not stabilize) indicates an intermittent connection within the fuel injector.








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5. Injector Specifications:
7. The Fuel Injector Balance Test portion of this chart (Step 7 through Step 11) checks the mechanical (fuel delivery) portion of the fuel injector. An engine cool-down period of 10 minutes is necessary in order to avoid irregular fuel pressure readings due to Hot Soak fuel boiling.

Customer:

ill try these.

Customer:

thanks tim

tims auto repair :

you are very welcome

Tim's Auto Repair, Mechanic
Category: Car
Satisfied Customers: 12744
Experience: Have owned a repair shop for 25 yrs.
Tim's Auto Repair and 13 other Car Specialists are ready to help you

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