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Old 10-05-2009, 04:10 PM   #1
joejoe3
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Default 2004 STI misfire in cylinder 4. New to Subaru, please advise...

Hi all,

I just recently purchased a 2004 Subaru WRX STi. There’s currently a misfire in cyclinder 4. I was a Honda guy before, so really green with how the Subaru engines work. After doing some research it seems like these are the following things to try.

1) Spark plugs (*Replaced but no luck, currently running one step colder. What is the gap size for our engine?)
2) Injectors, how do you clean these, check for o-rings?
3) Coil pack? How to I test them, do i swap it with cylinder 2?
4) Compression test... if so, what's the normal pressure in a cylinder for this engine?

Am I missing anything else? The idle is a little rough and also the previous owner told me that I need to top up the oil after awhile. Is it normal (*The oil part)?

Performance Modification:
Blitz Recirculating BOV
Rocket Rally Tune (Cobb AP V1)
720cc nismo injectors
JIC Titanium Catback matched to Cobb DP
Crucial Racing Exhaust Manifold (coated and thermal treated) matched w/ Grimspeed Crosspipe (coated and thermal treated)
DC Sport Up-pipe


Comment from Previous Owner:
Quote:
There is one problem though, the car idles a bit rough. This happened after all makes changed my spark plugs (about 3000KM after they changed it), so I brought it back to them. They said they checked it and think its an injector that's dirty. I put a OBD2 reader to it and it says its a misfire in cylinder #4. I have not had this fixed yet, but the car still drives fine without any signs of detonation, misfire or loss of power/performance (or any different then before the change) when driven.


Any inputs to this will be greatly appreciated!
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Old 10-05-2009, 04:16 PM   #2
Dan707
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My recommendation for you is to do a compression test ASAP. If comp. on cyl nr.4 really lower than the others you might have a broken ring land.
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Old 10-05-2009, 04:41 PM   #3
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Do the swap with the coil pack and install a new spark plug in #4. If good you are done. If #2 is now missing get a coil pack.
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Old 10-05-2009, 05:19 PM   #4
joejoe3
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do you just pull the coil pack accordingly from 2 to 4 on both ends?

Also, friend is recommanding me to start the car... while the car is running and unplug and replug the coilpack one by one. if i pull the #4 one and it makes no difference then it's the coil pack? But if i already know it's cylinder 4 then his method is not needed?

Broken ring land... how much is that to fix?
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Old 10-05-2009, 05:38 PM   #5
joejoe3
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Guys, would this work to determine if coil pack is bad?

From what my friend told me, if you unplug the coil pack connection while the car is at idle, when you pull a good coil pack the idle gets rough, but when you pull a bad one the idle will remain the same.

So if i swap the coilpack with 2 and 4, when i pull the coilpack from #2 and idle stays the same, did i just confirm the coil pack is the reason for the misfire?
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Old 10-05-2009, 06:31 PM   #6
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No #2 might be missing now or #4 still is.
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Old 10-05-2009, 07:00 PM   #7
joejoe3
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Quote:
Originally Posted by falcon_view View Post
No #2 might be missing now or #4 still is.
well, i will clear the CEL code first and then swap the coil pack. that way if the cel comes on and shows the misfire is at 2, then it's the coilpack?

i also notice the car oil level drops too... any relationship?
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Old 10-05-2009, 07:26 PM   #8
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Loss of oil can be three things not including turbo, oil leaking, you would see spots on the pavement, oil going past the valves and guides, and oil past the pistons. When and if you pull the spark plugs and find one or more are oily black that is the cylinder. If it were a V8 engine and it belched smoke at start up it would most likely be valve guides but on this type of engine not sure it would do the same.
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Old 10-05-2009, 09:13 PM   #9
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Losing oil and misfire on #4 suggests broken motor.

I'd do the compression test.


Quote:
here is one problem though, the car idles a bit rough. This happened after all makes changed my spark plugs (about 3000KM after they changed it), so I brought it back to them. They said they checked it and think its an injector that's dirty. I put a OBD2 reader to it and it says its a misfire in cylinder #4. I have not had this fixed yet, but the car still drives fine without any signs of detonation, misfire or loss of power/performance (or any different then before the change) when driven.
A "goober" modded subaru is kind of like a time bomb. Unlike a Civic, it's EASY to mess up a subaru. Idiot mounts a manual boost controller, turns it up and you get a damaged motor. Are you sure the current tune matches the injectors and other parts?
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Old 10-05-2009, 10:21 PM   #10
falcon_view
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Now that I have more time to post.

As MasterKwan suggests, using oil and misfiring is not a good sign. The engine will use some between oil changes under normal driving. If it uses more than a quart between changes it is going south. High rpms can cause it to use more oil than it normally would. If you clear up the misfire with a plug or coil change, to be safe do a compression check on all cylinders. If one or more are low more needs to be done, if not, keep you foot out of it and keep an eye on oil level and try to determine if it is a leak or using oil. Check for leaking oil get under the car and look signs of leaking oil.
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Old 10-05-2009, 11:05 PM   #11
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Quote:
Originally Posted by joejoe3 View Post
Hi all,

I just recently purchased a 2004 Subaru WRX STi. There’s currently a misfire in cyclinder 4. I was a Honda guy before, so really green with how the Subaru engines work. After doing some research it seems like these are the following things to try.

1) Spark plugs (*Replaced but no luck, currently running one step colder. What is the gap size for our engine?)
2) Injectors, how do you clean these, check for o-rings?
3) Coil pack? How to I test them, do i swap it with cylinder 2?
4) Compression test... if so, what's the normal pressure in a cylinder for this engine?

Am I missing anything else? The idle is a little rough and also the previous owner told me that I need to top up the oil after awhile. Is it normal (*The oil part)?

Performance Modification:
Blitz Recirculating BOV
Rocket Rally Tune (Cobb AP V1)
720cc nismo injectors
JIC Titanium Catback matched to Cobb DP
Crucial Racing Exhaust Manifold (coated and thermal treated) matched w/ Grimspeed Crosspipe (coated and thermal treated)
DC Sport Up-pipe


Comment from Previous Owner:


Any inputs to this will be greatly appreciated!
small vac leak (maybe a bov leak) happens to me sometimes
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Old 10-05-2009, 11:26 PM   #12
joejoe3
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you guys have been very helpful so far!

yes, the car was professionally tuned at a respectable shop. I was planning to revert the car back to stock down the road anything, so i'm in the process of finding stock parts on the for sale forum.

Aside from that, i'll take a look in my garage to check for any signs of oil leaks, and i'll top off the oil and see how much it actually consumes. Should i top it off just a bit under the "H" on the dipstick?
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Old 10-05-2009, 11:33 PM   #13
noonagon
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Quote:
Originally Posted by joejoe3 View Post
you guys have been very helpful so far!

yes, the car was professionally tuned at a respectable shop. I was planning to revert the car back to stock down the road anything, so i'm in the process of finding stock parts on the for sale forum.

Aside from that, i'll take a look in my garage to check for any signs of oil leaks, and i'll top off the oil and see how much it actually consumes. Should i top it off just a bit under the "H" on the dipstick?
do not switch coil packs, it will mess up the firing order and blow something up wont it?
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Old 10-05-2009, 11:35 PM   #14
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Hmm, you're just avoiding the whole messy "compression" issue then? If you have good compression, then it's probably a tune/injector/spark issue. If you have bad compression the motor needs to come out. It's very binary.

I'd want to know that first before I went any further.


Quote:
do not switch coil packs, it will mess up the firing order and blow something up wont it?
No switching the coil packs is a viable test. The coilpack doesn't know what cylinder it's plugged into, its the connector that plugs INTO the coilpack that determines this. Imagine a little thought experiment. If the coilpack mattered to the cylinder, subaru'd have to sell 4 different kind of coilpacks for each engine.
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Old 10-05-2009, 11:41 PM   #15
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Quote:
Originally Posted by joejoe3 View Post
well, i will clear the CEL code first and then swap the coil pack. that way if the cel comes on and shows the misfire is at 2, then it's the coilpack?

i also notice the car oil level drops too... any relationship?
its blowed up
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Old 10-05-2009, 11:50 PM   #16
noonagon
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Quote:
Originally Posted by MasterKwan View Post
Hmm, you're just avoiding the whole messy "compression" issue then? If you have good compression, then it's probably a tune/injector/spark issue. If you have bad compression the motor needs to come out. It's very binary.

I'd want to know that first before I went any further.




No switching the coil packs is a viable test. The coilpack doesn't know what cylinder it's plugged into, its the connector that plugs INTO the coilpack that determines this. Imagine a little thought experiment. If the coilpack mattered to the cylinder, subaru'd have to sell 4 different kind of coilpacks for each engine.
You show'd me lol, i guess i thought he was just going to take the whole thing off and switch them, wires and all and not unplug coils, sorry about that, thanks for the heads up
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Old 10-06-2009, 12:06 AM   #17
joejoe3
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The car has been driving fine so that's why I was going to try the no-cost trial and error before getting a compression test done. I was quoted 135 to have one done.

Yes, if i swap the coil pack between 2 and 4, BOTH ends needs to be swapped or it'll mess up the firing order.

Obviously i try not to think about the internals are the cause of it, but if all the testing with spark plugs, injectors or coil pack doesn't get rid of the CEL, a compression test would be done (*within this week).

I'm so new to the engine, I need to locate where the injectors and coilpack is. the engine bay is so tight, do I have to take out anything to access injector 2 & 4? I think someone said battery when I was researching. how about the other end of the coil pack?
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Old 10-06-2009, 12:20 AM   #18
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Do you know what a spark plug boot is? If so the coilpack and boot are one of the same part. It is bolted to the head with a 12mm head on the bolt. It is very close to the frame down there!!! #2 will come out easer than #4. Once you unplug the wires from the coilpack by pressing the retainer you my have to pry the black plastic tab out of the valve cover that holds the plug wires for clearance to drop the #4 coilpack/plug boot to the back and down and out. I did on my forester and #2 should come up and out.
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Old 10-06-2009, 12:31 AM   #19
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Thansk buddy, i'll take the free one!
Damn you're helpful.
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Old 10-06-2009, 01:46 AM   #20
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Google is my best friend.
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Old 10-06-2009, 02:13 AM   #21
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ok, car was parked in the garage for the past 3 nights, no oil puddles so that's good news.

Engine bay is so tight, i could just touch the injectors... i could only imagine swapping the coil pack what i need to remove just to access it.
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Old 10-06-2009, 07:18 AM   #22
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Quote:
Originally Posted by joejoe3 View Post
ok, car was parked in the garage for the past 3 nights, no oil puddles so that's good news.

Engine bay is so tight, i could just touch the injectors... i could only imagine swapping the coil pack what i need to remove just to access it.
I'll bet $5 that the motor is blowed up...#4 piston is done

with the engine running...take the oil filler cap off and

raw exhaust blowing outa the filler = blowed up

try it
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Old 10-06-2009, 09:28 AM   #23
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Also take good notice if the coil connectors clip (lock) are good if not means loose connections & eventually will give you also mis fire on cyl.
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Old 10-06-2009, 09:46 AM   #24
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listen to the Uncle....
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Old 10-06-2009, 10:13 AM   #25
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I agree that it's likely a blown motor. I had identical symptoms when my #4 was cracked.


As Scotty said, with the motor running, pull the dipstick and look for exhaust puffing out.
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