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Discussion Starter #1
Been diagnosing misfire codes 1301, 0300, 0301 and 0302 and want to rule out a mechanical problem.









Except for #3, all cylinders are under 10% and number 3 has a new piston and rings that are not broken in yet which explains the higher, yet I would think, still satisfactory reading.
 

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1 and 2 look good, 3 bad and 4 borderline O.K. But, to meaningfully answer your question one would need more info. Was the motor up to temp when you did the test? If not, redo after getting up to temp. Did you listen to the intake tract and exhaust pipe to determine whether the primary source of leakage is intake valve(s) or exhaust valve(s) or if no air noise in intake or exhaust then rings as you postulate for #3 cylinder. How many miles on motor?
 

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Discussion Starter #3
I ran it 5 minutes before testing and only 200 miles since replacing #3 piston and rings.
 

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I ran it 5 minutes before testing and only 200 miles since replacing #3 piston and rings.
Leakdown tests need to be done at normal operating temp.

When you replaced the piston and rings in number three did you hone the cylinder? 200 miles doesn't sound like enough to get new rings set. If you didn't hone the cylinder it could take even longer.
 

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Discussion Starter #5
The block on these engines can't be honed so no I didn't. I guess if the other cylinders are OK, it was warm enough. You're not supposed to remove spark plugs from an aluminum head until it's cooled down which is why I only ran it 5 minutes.
 

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Elise newb
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The block on these engines can't be honed so no I didn't. I guess if the other cylinders are OK, it was warm enough. You're not supposed to remove spark plugs from an aluminum head until it's cooled down which is why I only ran it 5 minutes.
Hmm. Learn something new everyday. I would never have thought to avoid honing the engine.
 
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