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possible misfire? when car is cold?


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This issue has been so hard to pinpoint...

 

I thought maybe it was the drivers side valve breather hose was not connected to the intake.. then i went to change the PCV valve which did nothing ( needed to be replaced)

 

I'm still baffled.. it only happens when the car is cold and has been sitting 3+ hours.. you start up the car and give the car a little throttle and it seems like it's got a misfire.

 

No CEL is on.. I have not did a seafoam yet because I just changed the oil, the plugs and wires are said to be new but not sure what plugs are in the car so I will have to check on that but I do have a sound file.

 

I was told could be the IAC needs to be cleaned but what part of the IAC do I clean with the cleaner?

Edited by 1-3-2-4
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Misfire not a product of a dirty IAC. Inconsistent idle speed more common failure. PCV flow not likely either...

 

I would remove and check the spark plugs, verify the wires are the correct fit to the plug, no carbon tracking on the plugs through the wire. Proper gap on the plug. (I would not recommend platinum, Iridium, or split-fire type plugs. Champion, Autolite are brands I would steer clear from as well)

 

USE NGK BKR6E-11 stock #2756 spark plug (any parts house that carries them, or Subaru dealer). Subaru wires are the best (fit, performance, longevity) SOA430Q115 (dealer)

 

I would suspect a fuel injector next, perhaps an O2 sensor.

 

Some folks use the NGK copper plug in your application, they just require more frequent changes...

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I would check to make sure there is no water in the spark plug holes. If there is, get the engine up to running temp, remove the wires and blow out the holes and wire ends with compressed air, let stand for a few minutes for the remaining to evaporate, re-assemble. If you can run the car in a dark environment, it is very easy to check for fouled wires and or coil by seeing the spark escape...

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