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Help. Can not figure out what is wrong.


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I have a 2006 Outback with intermittant misfire on cyl 3 and sometimes on cyl 4. This is what we have done so far:

Changed spark plugs. 

Changed wires

Swapped fuel injectors 1 & 3    and 2 & 4

Replaced coil pack.

Replaced heads and head gaskets.

 

After doing everything up to replacing the heads, all indications were that vehicle was misfiring because it was ingesting coolant ( because of common head gasket failure in 2.5 engines) even though coolant loss was very small and took a month to drop. Compression was #1-100lbs, #2 80lbs, #3 55lbs, #4 50lbs. , Convinced that the head gaskets were the problem, we pulled the heads, and discovered minute cracks in combustion chambers. We replaced the heads and after working out initial bugs, vehicle idled like new, smooth and quiet. But when driven it seriously lacked power. Fearing we had gotten the timing belt marks wrong, we disassembled and checked, but marks were spot on. After checking for clogged convertor ( by removing upstream O2 sensor and checking for excessive back pressure) we needed to reset codes. We reset codes and let it idle for 20 minutes. Perfection. Shut it off. Eat dinner. Go to take vehicle and we have misfire on 3 & occasionally on 4. Car is undrivable. My son says it is exactly what was wrong before we did anything. He also says that in the morning, after carhas cooled down, it will probably start and run fine. I will check in the morning. Suggestions?

Edited by Charles D Scheiner
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Your compression numbers are far too low for a running engine, those only indicate the compression test may have been done incorrectly or the guage was faulty.

 

The engine you have doesn't typically leak coolant internally. That was a major failure mode on the 96-99 EJ25 engine, but 2000 and later tend to only leak externally.

 

Minute cracks in the combustion chambers are nothing more than casting marks from the sand or foam form used when the head is manufactured.

 

Is the misfire constant? A constant misfire will generally make the CEL flash. If you were to unplug the injector for cylinder 3 does it change the "shake" of the engine at all? How about for the other cylinders?

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some scanners can get "freezeframe" data like my old Innova. There are cable-connected laptop options and even cheap ($15) bluetooth adapters for smartphones running Torque or similar apps. They are able to read more data than just codes. Or maybe AutoZone can - or rent you a scanner that can.

 

Might not mean that info would be definitive, but it might give us some clues.

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