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Old 03-07-2006, 06:58 PM   #1
xclover
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Subaru Stars 2.5 DOHC Engine Problem (98 Forester)

I have a 1998 Subaru Forester. I have had problems getting a cylinder one misfire. I decided to get different heads and change them out thinking maybe I had a valve problem. I changed the heads and I'm still getting the same problem. I put '96 heads on my '98 block so that I have hydraulic lifters. When the engine idles it shakes slightly. After driving for about 300 miles the check engine light will blink for a little while and then continue to shine steadily. I do not have any problems with loss of oil, coolant, or any other fluids...in fact I put all new seals in the motor when I had it apart. The walls of the cylinders were in perfect shape, nice and smooth. You can actually hear it misfire through the exhaust. I even changed out the coil thinking that may have been the problem.

I do not know what else to try to fix this problem, PLEASE help me if you have any recommendations!!

Thank you in advance!!

-xclover
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Old 03-07-2006, 07:04 PM   #2
andys
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DUDE, check the check engine light code. Get an OBDII reader.
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Old 03-07-2006, 07:11 PM   #3
xclover
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I do have a code reader, that is how I know it is a cylinder one misfire.
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Old 03-07-2006, 07:14 PM   #4
yebokmj
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I'm assuming you did a compression check?
My MY97 DOHC was having this problem and it was because cyclinder #4 was down to like 45psi.
Joshua
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Old 03-07-2006, 07:42 PM   #5
xclover
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Yes, I did a compression check on all cylinders. They were all testing good. I will re-test again. What does it mean if the compression is low?
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Old 03-07-2006, 08:01 PM   #6
yebokmj
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Well if the compression is low it could be a few things but considering you changed heads it pretty much could only mean piston problems. Most likely a piston ring.
I also was assuming you checked your spark plugs and wires before going through the heads swap. A wire or a spark plug could also cause your problem.
Joshua
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Old 03-07-2006, 08:19 PM   #7
andys
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yup -When I was having a terrible time with misfireing some new properly gapped plugs did wonders.
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Old 03-07-2006, 08:20 PM   #8
xclover
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Ok, I will look over some things again. Wouldn't I be burning oil if the rings were bad? If you can think of anything else I should look at, I would really appreciate it!

Thank you!
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Old 03-09-2006, 08:59 AM   #9
xclover
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What are the spark plug gapping specs for this engine?
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Old 03-09-2006, 09:02 AM   #10
yebokmj
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off the top of my head I want to say 42-44 but a quick search of the NA forum or a look in your owners manual will give you the answer.
Why your starting to think that might be your problem?
Joshua
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Old 03-10-2006, 10:32 AM   #11
xclover
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Not sure if this is my problem...but I am really getting at the end of my rope trying to find out. The motor runs nice and strong, but that annoying check engine light and shake at idle is really annoying me!!! Have you heard of this piston slap that these engines have? I was told they "tap" since there are no skirts on the pistons.
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Old 03-10-2006, 10:53 AM   #12
yebokmj
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I'm assuming you've checked for vacume leaks as well? That can effect idle, might cause the missfires.
Joshua
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Old 03-10-2006, 11:27 AM   #13
Matt Monson
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BTW, this thread would get 3-4x as many replies over in the NA forum. Since this is a forum for swaps, most of the members here are turbo specialists.

My first question to you would be what octane fuel are you using? Do you realize the '96 heads had a smaller combustion chamber than your stock heads and that the '96's required premium gas because of their CR?
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