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Old 08-30-2021, 03:04 PM   #1
mava1395
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Default Misfire at idle, have done some things but still at a loss

I have a 2007 STI and I have been having an issue of misfiring at idle. I cant seem to pinpoint the problem. I am getting a p0304 or a misfire in cylinder 4. The car is only misfiring lower than about 1000 rpm and does it intermittently. So it will misfire for a few seconds then clear up for another few. Then misfire for a few more then clear up again. I checked the injector on cylinder 4 and even replaced it with another brand new stock injector and the issue is still there. I changed coils around and the misfire is still on cylinder 4. I even changed out the plugs and it's still having the same issue. I checked for vacuum leaks, fuel leaks, anything leaking but everything checks out. My fuel pump when priming is very loud. It's a walbro 255. I wanted to see if a bad fuel pump could possibly cause a misfire in cylinder 4 because I know it already runs lean as it is. Please help!!!
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Old 08-30-2021, 03:25 PM   #2
JSR84
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Compression and leak down test.
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Old 08-30-2021, 06:35 PM   #3
mava1395
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Quote:
Originally Posted by JSR84 View Post
Compression and leak down test.
Should I get all 4 checked? Or just the one?
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Old 09-04-2021, 01:17 PM   #4
13WRXGrey
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Quote:
Originally Posted by JSR84 View Post
Compression and leak down test.
2nd this

Might as well do all 4. I would for peace of mind.
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Old 09-04-2021, 03:54 PM   #5
JSR84
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Quote:
Originally Posted by mava1395 View Post
Should I get all 4 checked? Or just the one?
Might as well, but do 1 first, if it shows a bad result, itíll save you from having to do the rest
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Old 09-05-2021, 08:46 AM   #6
Jp925
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Howís your oil consumption? How many miles on the motor?

For what itís worth I had this exact issue on my 06, car would throw misfire codes under 1200, as long as I was above that I was ok. a leak down test confirmed 2 toasted exhaust valve seals. I pulled the motor and the heads, and ended up doing a complete rebuild for the piece of mind.


Quote:
Originally Posted by mava1395 View Post
I have a 2007 STI and I have been having an issue of misfiring at idle. I cant seem to pinpoint the problem. I am getting a p0304 or a misfire in cylinder 4. The car is only misfiring lower than about 1000 rpm and does it intermittently. So it will misfire for a few seconds then clear up for another few. Then misfire for a few more then clear up again. I checked the injector on cylinder 4 and even replaced it with another brand new stock injector and the issue is still there. I changed coils around and the misfire is still on cylinder 4. I even changed out the plugs and it's still having the same issue. I checked for vacuum leaks, fuel leaks, anything leaking but everything checks out. My fuel pump when priming is very loud. It's a walbro 255. I wanted to see if a bad fuel pump could possibly cause a misfire in cylinder 4 because I know it already runs lean as it is. Please help!!!
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