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Old 06-24-2005, 07:12 PM   #1
hwy61
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Default OK hotshot mechanics, best guess.

'05 STI with 28,000 miles. Running rough again at idle. New coil and new plug on #2. Ran better for a short while, cel back on, back to Subaru, misfire on #2 again. Compression test, about 160 everywhere but #2 - 115.

Under warranty, Subaru will fix beginning first of next week. Anybody want to go down in history as best mechanic. What's your idea of the problem. Stock everything. Radiator check indicates oil to the full mark, blinker fluid is up to snuff, muffler bearings are in good shape and the tires have new factory air. Oh yea, color is black with little pink STI badges. a good weekend to everyone. hwy61
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Last edited by hwy61; 06-26-2005 at 06:07 PM.
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Old 06-24-2005, 08:18 PM   #2
Godmal
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Slightly bent valve, maybe?
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Old 06-24-2005, 08:21 PM   #3
8Complex

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Mod list would help. Probably a broken ring land.
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Old 06-24-2005, 09:03 PM   #4
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Recheck blinker fluid and reinspect muffler bearings haaa haaa.Did you follow proper break in on the motor.Anys mods?
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Old 06-24-2005, 09:51 PM   #5
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How does the oil look? Is there fuel in it? Is there coolant in it?

How does the coolant look? Is there oil in it?

Do a leakdown test on cyl #2. That will tell you exactly where your compression is going.
A leakdown test simply puts air into the cylinder so you can hear/feel where it's going.
If it comes out the exhaust, it's a bent or burnt exhaust valve.
If it's going into the intake, it's a bent or burnt intake valve.
If it's going into the crankcase, it could be blown rings or a burnt/broken piston, or a headgasket.

I'll take a wild random guess and say headgasket.

I also have a skip at idle. I'll check my compression tomorrow. I really hope it's just something to do with the AP.
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Old 06-24-2005, 10:25 PM   #6
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cel code would also help to find out the problem
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Old 06-25-2005, 12:10 AM   #7
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Over a 90% chance it is broken ring / rings and or ring lands on #2 due to detonation.

Larry
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Old 06-25-2005, 12:41 AM   #8
Wombat North
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Quote:
Originally Posted by hotrod
Over a 90% chance it is broken ring / rings and or ring lands on #2 due to detonation.

Larry
2nd that
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Old 06-25-2005, 02:34 AM   #9
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Let's see, No oil in radiator, no water in oil, cel code is "misfire #2 cyl", don't know the actual code # it's throwing, everyones diagnostic equipment says the same though. Car seems to run fine at high RPM, plenty of power, no unusual noises, no smoke, uses 1 qt Mobile 1 every 3000 miles, always has just like my previous modded '02 WRX. No fuel in oil, normal gas mileage, starts fine, idles rough.

Had a turboXS turbo back system on it, took it off for dealer work. Said he couldn't work on it under warranty until I made it stock. So I made it stock. Had a UTEC installed and factory harness was running through it although it was set to base mode waiting for me to get to Atlanta for tuning which is where I'm going after I get this problem fixed. Took that off also, might have accidentally failed to tell em about that one. Engine has never hit rev limiter or had a fuel cut. most boost ever about 15.5. Boost increaes with the tbx exhaust installed. No boost creep.

Engine was driven at various speeds when new. Left original oil in for 4,000 miles per dealer recommendations, changed oil/filter then using a high quality regular 10w30. At 7000 miles changed oil/filter installed mobile one and it's been mobile 1 since with a change every 3000 mi including Subaru OEM filters. Air filter has been changed twice. No boost control installed increasing boost.

Car driven fast and hard, couple of SCCA solo II days but everything well maintained. Problem occurred at appx 20,000 miles. No worse, no better, rough idle. hwy61
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Old 06-25-2005, 02:44 AM   #10
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choices would seem to be: burned valve, burned/cracked valve seat, head gasket, rings, crack in piston, cracked head, warped head, bent intake valve, what else??? Engine always had a tapping noise that people would ask me about. Sounded like a lifter needing adjustment type tapping. hwy61
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Old 06-25-2005, 02:53 AM   #11
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And another Subaru dealer told me it was the front wideband 02 sensor that was the problem and it was not under warranty as it had a modded exhaust I purchased and installed Subaru OEM 02 sensor and that didn't fix it. Waste of $180 except a club member had a new STI that was broken down needing this part and a fuse. Old one got him running and he now owes me all the beer I can drink for a year. hwy61
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Old 06-25-2005, 07:36 AM   #12
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Vry common problem. Search other Suby sites. You'll find problem with many different models. Cures range from TLC to complete motor teardown. I had this, never found out why. Took out motor 2x and rebuilt it. Wasted a EJ20, bought another, had heads rebuilt, and guess what, still had mis-fire codes. Changed everything (for other reasons) still there. Threw away stock ECM, problem gone.
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Old 06-25-2005, 11:37 AM   #13
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hydra and be done with it? I have had the same problems with my sti I do bi-weekly comp tests and never seen anything to raise a flag all 4 cyls with in 2-3 psi of each other. have yet to do a leakdown but soon. 28,000 on the clock. the thing with the hydra is I have no one even close to me to tune it. OKlahoma sux.
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Old 06-25-2005, 01:54 PM   #14
hwy61
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Would like to get rid of CEL but it's the rough idle that's buggin me. Low compression on #2 cyl + rough idle don't add up to something ECU can fix. hwy61
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Old 06-25-2005, 02:03 PM   #15
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Slingshot, you're right on track but they know something serious is wrong and i'ts going to have to come apart regardless so they figured no point is trying to pinpoint the exact problem at this point. I think I will try to get them to check the other head also to make sure there is no evil underway there. I think I'm about the only Subaru they see anymore as they have quit selling them. Good mechanic though, he is the Subaru mechanic, friendly and very cooperative. Doesn't ask any embarrasing questions. hwy61
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Old 06-25-2005, 04:07 PM   #16
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Befor you spent crazy money, search this, and other suby sites. i had two different wrxs, with three different motors, and different everything, and i had mis-fire codes. Your motor could be fine, and it probably is.
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Old 06-25-2005, 06:07 PM   #17
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Quote:
Originally Posted by turbo2ner
Befor you spent crazy money, search this, and other suby sites. i had two different wrxs, with three different motors, and different everything, and i had mis-fire codes. Your motor could be fine, and it probably is.

so what your saying is the stock ECU is the culprit even if a UTEC is involved. and a stand alone will correct this problem? am i reading this right.
Mav
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Old 06-26-2005, 12:23 AM   #18
hwy61
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Quote:
Originally Posted by turbo2ner
Befor you spent crazy money, search this, and other suby sites. i had two different wrxs, with three different motors, and different everything, and i had mis-fire codes. Your motor could be fine, and it probably is.
I'm not spending any money, under warranty, but HOW? can the ecu correct 115 psi in #2 when other cylinders are 160? Put you guess in. Will know the answer next week and I doubt the engine is ok. 115 psi on #2 doesn't sound like it's OK and the rough idle is really aggravating.
hwy61
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Old 06-26-2005, 01:59 AM   #19
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i have a similar rough idle. I have 19k miles on my 05 sti and the problem started about 2k miles ago and was mild. Couple days ago i was at an in-n-out drivethru and heard and felt two loud poping noises from my car like it misfired tr something. The car hesitated for a couple seconds and then idles back to place again. no CEL.
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Old 06-26-2005, 05:26 PM   #20
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Quote:
I'm not spending any money, under warranty, but HOW? can the ecu correct 115 psi in #2 when other cylinders are 160?
It can't, Low compression means you have a mechanical problem, blown head gasket, bad valves, or broken piston or piston rings, or loose spark plug. Low compression does not get better until you fix it.

Larry
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Old 06-26-2005, 05:58 PM   #21
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Because the new spark plug fixed the problem temporarily im going with broken ring/land/scarred cylinder wall. If it was an oil seal on a valve he would see smoke at start up.
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Old 06-26-2005, 06:03 PM   #22
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agree 100% Larry, we will know before the weeks over, this thread is for everyone that thinks they're a great mechanic to post their diagnosis.

Hye-Teck, that was a drive by at the drive in. hwy61

Last edited by hwy61; 06-27-2005 at 02:42 PM.
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Old 06-26-2005, 06:11 PM   #23
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I'll rule out a head gasket only because I haven't heard of one blowing on these motors (anything is possible though). Next, the valves on that head (#2) is more likely to be culprit than a head gasket but still not something you see everyday. However, I recently had a set of heads rebuilt and I received a call from the machine shop stating that when they went to turn the valves that 5 of them were bent. I really don't know how that happened. The most likely as was said several times is a cracked ringland, which seems to be something that you see nearly often around hear Also, the rough idle would give further attention to this. Many of these cracked/broken ringlands are a result of higher than stock power levels and a tune that left something to be desired.
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Old 06-27-2005, 10:54 AM   #24
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A broken ring land won't necessarily show itself on a compression test. Do a leakdown.

Frank
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Old 06-29-2005, 10:37 AM   #25
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Any info yet?
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