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Old 02-25-2011, 06:22 PM   #1
DrakeMK3
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Default misfire on cylinders 1 & 4

Hey everyone, I've done a search, but haven't found anything yet.

I have a 1999 outback limited with a EJ25D that I just rebuilt and I'm now having what seems to be a misfire occur on cylinders 1 & 4. I don't have any check engine codes, but I used a timing light to verify something was amiss (pardon the pun). The timing light I'm using is digital and I can read the engine rpm as well. This is where it get's confusing for me. When I check the timing, it is rock steady at 15 degrees (what it is supposed to be), but I notice an erratic light pattern when on cylinders 1 & 4. In addition, the car's tach reads 700 and I can confirm that with the timing light on cylinders 2 & 3, but when the timing light is clamped on 1 & 4, the tach speed is double on the timing light. In addition, the vacuum is reading low (15 inHg) which could be a result of the erratic firing issues.

I'm using new plugs, wires, cleaned IACV w/ new gasket. I'm not sure if it is timing related or not. I followed the diagram and even counted teeth to confirm I installed the timing belt correctly. Does anyone have any suggestions?

Any help is appreciated. Thanks!
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Old 02-25-2011, 11:45 PM   #2
kgeezy
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do a compression test
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Old 02-25-2011, 11:56 PM   #3
BAN SUVS
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I'm confused. Is there anything wrong when you're not trying to use the light?
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Old 02-26-2011, 01:12 PM   #4
DrakeMK3
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I figured someone would mention a compression test next. I'm going to do that and will post my results.

Regardless of using the light or not, it will still have a rough idle. I took the coil pack off and tested it, but I think the specs in my haynes manual are wrong because I tested a brand new coil pack and was getting the same results as the one I already have. ARGH!

In any case, when I have a timing light on it, the rpm's now read as they are supposed to. This is super confusing!
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Old 02-26-2011, 05:02 PM   #5
DrakeMK3
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Here's an update, after doing some more digging around, my timing might be off by a tooth. This could cause all the problems I've experienced so far. I'll update this thread when I can test my theory.
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Old 03-04-2011, 08:09 PM   #6
DrakeMK3
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Here's an update. I do not have a misfire on cylinder 4.

The compression on cylinder 1 is only 90 psi. Performing a leak down test revealed that I have a leak on the intake and exhaust side. This tells me that the valves need to be adjusted or they are bent. I don't think they're bent because I followed all proper procedures when installing the heads, timing belt, etc.

So, could the machining for new valve seats have thrown the valves off so much that they all need to be readjusted to get full compression? Thanks!
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Old 03-04-2011, 08:37 PM   #7
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any change to any part of the valve train would usually require a lash adj, but I don't know if the EJ25D has solid lifters or HLA's. if they are way too tight, then they might not close fully and cause a leak. a bad valve job could do the same even if adjusted correctly. Were the valves and seats lapped?
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Old 03-04-2011, 09:28 PM   #8
DrakeMK3
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Yes, I had them grind new valve seats and lap the valves.
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Old 03-04-2011, 10:21 PM   #9
DrakeMK3
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It's just the one cylinder though, so that's what makes it so weird.

I've got 160psi on 2 cylinders, 145 on one, and 90 on this one.
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Old 03-12-2011, 09:20 PM   #10
DrakeMK3
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Update:

Did a leak down test and cylinder 1 has 90% loss. So, I took the cylinder head off and the valves all look fine, but I've only removed one of the intake valves to check. I don't see any cracks, but I'm starting to wonder if the head has fissures beginning to form. I examined the piston and it physically looks fine.

I am at a complete loss on this one. I will probably take the head to a different machine shop and have it re-examined. Hopefully, they'll find something wrong so I can sleep at night.
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