XJ XJ8 / XJR ( X308 ) 1997 - 2003

Code P0300 Random/multiple cylinder misfire detected..and others

Old Feb 14, 2023 | 11:37 AM
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Default Code P0300 Random/multiple cylinder misfire detected..and others

Getting all of these codes at one time. Any ideals. Thanks

Code P)300 Random/multiple cylinder misfire detected..
also getting code p0357 ignition coil G, P0 356 ignition coil F, and P0 351 ignition coil A.
 
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Old Feb 14, 2023 | 12:30 PM
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Helpful to know the kilometres/miles on the vehicle.

What is the battery voltage across the terminals with the ignition in the OFF position when measured with a voltmeter?

What is the fuel pressure?

Are the cam cover seals leaking?

Have the spark plugs been replaced?
 

Last edited by NBCat; Feb 14, 2023 at 12:30 PM. Reason: Add missing words
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Old Feb 16, 2023 | 04:20 PM
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Originally Posted by NBCat
Helpful to know the kilometres/miles on the vehicle.

What is the battery voltage across the terminals with the ignition in the OFF position when measured with a voltmeter?

What is the fuel pressure?

Are the cam cover seals leaking?

Have the spark plugs been replaced?
battery voltage 14.5 running , fuel pressure 41.1 fuel pump replaced 10k miles ago l
75k miles on car
spark plugs and coils replaced about 20k miles ago
cam cover seals not leaking
 
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Old Feb 16, 2023 | 04:50 PM
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I would replace the coils and plugs on the noted cylinders, and realize the other coils are
not far behind.
 
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Old Feb 16, 2023 | 05:04 PM
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Originally Posted by RandyS
I would replace the coils and plugs on the noted cylinders, and realize the other coils are
not far behind.
seams so odd 3 coils
or plugs would go out at same time.
 
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Old Feb 17, 2023 | 10:10 AM
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Ebay ignition coil set
​​​​​​New copper spark plug set unless your plugs are new
vacuum leak if there's any then get silicone hose
Clean the maf
pour techron injector cleaner into the gas tank
​​​​​
 
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Old Feb 17, 2023 | 10:21 AM
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Originally Posted by leaddog11
battery voltage 14.5 running , fuel pressure 41.1 fuel pump replaced 10k miles ago l
75k miles on car
spark plugs and coils replaced about 20k miles ago
cam cover seals not leaking
Voltage needs to be checked with ignition OFF using a voltmeter. Minimum available voltage for all modules to correctly function is 12.6 volts across the terminals.

Remove the spark plugs from the cylinders indicating misfires and inspect for oil in the spark plug wells. Oil fouling is a major cause of ignition coil failures.
 
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Old Feb 17, 2023 | 11:19 AM
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Originally Posted by NBCat
Voltage needs to be checked with ignition OFF using a voltmeter. Minimum available voltage for all modules to correctly function is 12.6 volts across the terminals.

Remove the spark plugs from the cylinders indicating misfires and inspect for oil in the spark plug wells. Oil fouling is a major cause of ignition coil failures.
Thanks. voltage engine off 12.7 engine idle 14.5. sounds about right.
will check for oil.
odd when running and skipping and restricted performance and check engine light showing... When I clear the codes it runs perfect for about 4 seconds .
 
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Old Feb 20, 2023 | 07:47 PM
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You could swap some of those coils around and see if the fault follows to the other cylinders. Not and expert but it does sound like coils to me as well....
 
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Old Feb 21, 2023 | 06:35 AM
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Originally Posted by David N. Warner
You could swap some of those coils around and see if the fault follows to the other cylinders. Not and expert but it does sound like coils to me as well....
thanks
 
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Old Feb 23, 2023 | 11:18 AM
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I swapped coils around. same coil codes as before. A, F, G no oil in holes. Will try maf sensor next
 

Last edited by leaddog11; Feb 23, 2023 at 11:40 AM.
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Old Mar 17, 2023 | 11:33 AM
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UPDATE...hard to believe one bad coil could cause all these codes. But that is what it was. Runs great now.
 
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