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P0304: Issue solved!


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38 replies to this topic

#1 211

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Posted 04 June 2009 - 08:05 PM

2000 OBW 111k. front O2 sensor at 80k, Timing Belt, pulleys, WP, etc. 103K along w/ new plugs (NGK of course).

This originally started as a Knock Sensor CEL code thread titled High-pitched whine, jerky acceleration, rough idle, check engine light
I've since replaced the knock sensor but when I went to clear the code there was a second code; P0304- Misfire Cylinder 4.
Wires look great (OEM Subaru) and I believe they were changed at 60k but just to double check, I swapped the cylinder 4 wire with cyl. 2 and cleared the code. Code came back about 5 miles later as cyl 4 misfire (P0304).

I do tune ups regularly and plugs look mint (just checked)!

I need some advice as to what to check next? I've read that there's a pretty simple technique to checking the ignition coil but I don't have a manual. Can someone give some steps for coil diagnosis?

Also, what else should I be looking for?

Worst case is it's the valves from what I've read :eek:

EDIT~
Just talked on the phone w/ a buddy who has a manual. My coil appears to check out OK. Here's what we did: Measure resistance between the 1-2 coil terminals @ 13.6Kohm and 13.9Kohm between terminals 3-4. Spec is IIRC between 10-15k. Also Ohm'd out all the wires and they're within spec.

Edited by 211, 16 June 2009 - 07:39 PM.
resolved issue- updating


#2 nipper

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Posted 04 June 2009 - 11:21 PM

Your too high tech.

First inspect the spark plug boots for any sighns of oil. Leaking spark plug gromits will degrade the wires and cause a miss.

secondly get out the water. In the evening soak the wires with water and the coil and look for sparklies. A meter wont show hairline cracks in the coil towers.

How old are the plugs?


nipper

#3 grossgary

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Posted 05 June 2009 - 07:25 AM

look carefully like nipper said.

i had a spark plug go bad last year. brand new, ended up cracking shortly after install causing cylinder misfire on a friends car.

i have seen things test within factory spec's before but still cause CEL's, so while they are extremely reliable almost all of the time, don't put all your eggs in that basket either.

good luck, these kind are annoying.

#4 Bmm001

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Posted 05 June 2009 - 07:59 AM

A few weeks ago, my '03 outback started missing/stumbling when it was cold. Interestingly, it didn't throw any codes. Turned out the #4 spark plug boot was torn, and the valve cover gaskets were leaking a bit. New wires/plugs, spark plug grommets and VC gaskets, and now it runs beautifully!

Brian

Edited by Bmm001, 05 June 2009 - 07:59 AM.
spelling


#5 211

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Posted 05 June 2009 - 09:35 AM

First inspect the spark plug boots for any sighns of oil. Leaking spark plug gromits will degrade the wires and cause a miss.

secondly get out the water. In the evening soak the wires with water and the coil and look for sparklies. A meter wont show hairline cracks in the coil towers.

How old are the plugs?
nipper


Plugs were replaced at 103k when I did the timing belt (now at 111k) so 8,000 miles ago. No oil at all on any of the boots.
I will try the water method tonight and give an update.



One other thing I might add. The car idles rough, has a noticeable lack of power under acceleration. I'm not sure if this misfire code is happening all the time or just once in a while, but as mentioned, the car runs rough ALL the time.
Also, while driving around yesterday after swapping #2 & #4 wires the CEL started blinking.
A Subaru buddy of mine says a blinking CEL means the engine is "CURRENTLY" misfiring.
Any truth to that?

Thanks for the help guys- I'll be back...

#6 nipper

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Posted 05 June 2009 - 09:57 AM

Blinking means an active misfire and you can be potentially damaging your cat.

It sounds like you may have a bad wire.

Also remove the plugs and check them. Even the best mechanics on occasion crack a plug on install and dont realize it.

nipper

#7 211

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Posted 06 June 2009 - 10:10 PM

Okay, replaced the air filter, and plugs (no dealers open on Saturday to buy wires).
I'm scared now because I pulled #1 & 3 plugs and there's unburned fuel on the ends.

The first time I checked the plugs back in the beginning of all this, it had been sitting for a few hours so the plugs looked normal. This time I had to start the car and back it out from under the carport so I could get some light. Ran for maybe 1 minute, and shut it off to change plugs. When I got to the passenger side plugs, they were BOTH wet with raw gas!

Started up after the plug change and still runs poorly, CEL flashes madly.

OMG what is happening to my car!?!

#8 nipper

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Posted 06 June 2009 - 10:20 PM

Is there a new timing belt tensioner in the car?

nipper

#9 211

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Posted 06 June 2009 - 10:25 PM

Yeah, 103k miles. All new belt, idlers and tensioner.
Car's at 111k now...

#10 nipper

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Posted 06 June 2009 - 10:30 PM

Unburnt gas on two cylinders on the same bank. I would start with a compression check and or a vaume gauge. With it being on cylinders 1 and 3 you can rule out the coil, and its just a longshot to have two bad fuel injectors. Maybe a vac leak on the intake manifold on that side of the engine?

When you use a vac gauige, tell us exactly what the needle is reading.

Did you use OE parts?

#11 211

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Posted 06 June 2009 - 10:40 PM

Not sure what a vacuum gauge looks like or what it's supposed to do? I assume you hook it to a point in your vacuum system (plug the other end?) draw a vacuum and notice if the pressure drops off?

The timing belt kit was an ebay kit (PCI if I recall). I did a lot of searching and they seemed pretty solid.

Compression test will be next. I don't have one though...

#12 nipper

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Posted 06 June 2009 - 10:42 PM

http://www.classictr...cts/vac/uum.htm

#13 211

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Posted 06 June 2009 - 11:34 PM

Did a bit more digging here on the forums. Tried the "dollar bill" test and the exhaust wants to suck the bill in momentarily a couple times per revolution.

There's a definite unsteady exhaust sound, like "put-put-p-put-p-p-put-put-p-put...

What are the chances that the belt could've skipped a tooth on the RH side cam?
From what I understand the dollar bill trick helps determine a bad valve. But does the valve HAVE to be bad? If it jumped a tooth, wouldn't the engine exhibit the same symptoms?

#14 nipper

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Posted 07 June 2009 - 08:01 AM

I think it ihas ju,ped a tooth or two. A compression test or a vac gauge can tell that (the compression test moreso). Then they next question would be why did it jump a tooth? Were all the idlers and tensioner replaced? Is there a bad sprocket?


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#15 211

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Posted 07 June 2009 - 10:40 AM

I think it ihas ju,ped a tooth or two. A compression test or a vac gauge can tell that (the compression test moreso). Then they next question would be why did it jump a tooth? Were all the idlers and tensioner replaced? Is there a bad sprocket?


nipper


Yes all idlers and tensioners were replaced at 103,000 miles (2k miles early) with new parts from a PCI kit. I did not reuse anything timing related.

I don't have a vac or compression gauge. Today I'll pull the covers and see what I can find.
Sprockets looked fine when I had it apart during the timing change. In fact the whole engine looked incredibly clean and "new".

#16 211

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Posted 07 June 2009 - 01:30 PM

I just pulled the timing covers and all marks line up. There's 47 teeth on the passenger side and 43.5 teeth on the drivers side.

I started another thread regarding a more serious concern! Why the threads of the crankshaft bolts are wet with what smells like fuel and oil!!!

#17 211

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Posted 07 June 2009 - 07:39 PM

Kay, update.
I've got a neighbor that has the same y/m/m as my 02 outback. I talked him into letting me swap out some parts so I could help isolate this issue.

I swapped out my coil pack with his and still misses (you can hear it in the exhaust).
Swapped out my spark plug wires with his and still misses. My plugs are totally new. Bought a set of NGK's yesterday just for this issue.

Here's the weird part...
I dusted off the old timing light and connected it to all 4 wires one at a time to get an understanding of what the spark is doing. Only one cylinder (#1 cyl) flashes with any real steady pattern. All the others (especially #4) are very erratic, #3 flashes erratic and at times really slow; even my neighbor said, it looks like its wanting to stop all together.
...and I did make sure to seperate the wires as much as possible to avoid any stray inductance from the adjacent wire.

Maybe I'll post a video...

#18 johnceggleston

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Posted 07 June 2009 - 07:55 PM

the it has to be the igniter??? maybe.

#19 211

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Posted 07 June 2009 - 09:09 PM

the it has to be the igniter??? maybe.

Isn't the igniter internal to the coil? If not where is it located? Remember I swapped out the coil pack with one out of my neighbors OB.

#20 nipper

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Posted 07 June 2009 - 10:31 PM

I just pulled the timing covers and all marks line up. There's 47 teeth on the passenger side and 43.5 teeth on the drivers side.

I started another thread regarding a more serious concern! Why the threads of the crankshaft bolts are wet with what smells like fuel and oil!!!



What are you calling crankshaft bolts and how are you getting to them?

Counting teeth means as much as a 3.00 bill in a candy store. You have to check the alignment marks on the cams and crank.

Untill you stop freaking out and start properly diagnosing your not going to get any answers. I dont trust any parts but subaru when it comes to the timing belt but thats just me.

And change only one thing at a time when trying to diagnose something, otherwise you are digging a deep hole we cant help you out of.

Lets do a poor mans compression test. Pull plug wires one at a time, is there any change in the way the engine runs?

nipper

#21 nipper

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Posted 07 June 2009 - 10:34 PM

Isn't the igniter internal to the coil? If not where is it located? Remember I swapped out the coil pack with one out of my neighbors OB.



Its not the "ignitor" if it was it would be random cylinders. Soobys fire 1-2 and 3-4 together. If it was a bad coil you would have a 1-2 or a 3-4 misfire, not a 1,3 misfire. a 1,3 issue is usually a timing belt issueor a cam issue.


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#22 211

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Posted 08 June 2009 - 12:09 AM

What are you calling crankshaft bolts and how are you getting to them?

Crankshaft pulley bolt. I'm not even ready to go there yet. I'm just hoping when I did the timing belt at 103 I followed the book by putting oil on the threads and that's what it was.

Counting teeth means as much as a 3.00 bill in a candy store. You have to check the alignment marks on the cams and crank.

Of course I had the marks lined up when I counted the teeth


And change only one thing at a time when trying to diagnose something, otherwise you are digging a deep hole we cant help you out of.

I have been; plugs, double check timing, swap coil, swap plugs etc. I didn't do all those things at the same time. I start the motor after each configuration. Of course I had to give my neighbor his coil and wires back.

Lets do a poor mans compression test. Pull plug wires one at a time, is there any change in the way the engine runs?

nipper


I'll pull the plug wires one at a time tomorrow. I did today but I can't recall exactly which ones made the engine run 'worse'. I know one plug didn't seem to make a difference.

...and I apologize for "freaking out" but yeah, I am a little bit. This is my family/go to work vehicle and I really can't afford to put my kids on a Ramen noodle diet so I can have the heads rebuilt. This is just not a good time.
...of course- I'm thinking worse-case at this point.


Go figure too... we JUST paid this car off less than a month ago :banghead:

Edited by 211, 08 June 2009 - 12:18 AM.


#23 unibrook

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Posted 08 June 2009 - 01:33 PM

Listen carefully. Does it misfire ALL the time? or only when warm? If only when warm, and mostly under load, then humor me and replace your front 02 sensor (yes, do it again). My 2001 Forester needs a new front 02 sensor every 40k miles. Then report back here.

#24 211

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Posted 08 June 2009 - 05:41 PM

@ unibrook.
Misfires ALL the time. From the second I start it up, through the warm-up.

UPDATE:
I managed to get my hands on a compression and vacuum gauge; also went out and purchased a Chilton manual. :rolleyes: ...never had problems, never needed one, till now.

Did a vacuum check per manual; readings were rock solid at 20" fully warmed up at idle. However, as soon as I touched the throttle to increase rpms it would flick back and forth +/- 3-5". But I could also hear and feel the engine 'missing' while increasing the rpms. Once I dropped to idle it stabilized at 20".

Also did a compression test per manual instructions. All four cylinders exhibit the same results and had the same end pressure readings of between 200-220psi. Each cylinder took approx 4 cranks to reach maximum compression. Within the 4 cranks these were the results per cylinder (did each cylinder twice just for an average):

1= 145, 175, 200, 215
3= 140, 175, 200, 210
2= 140-ish, 160, 210, 220
4= 145, 170, 200, 215

So based on the vacuum and compression readings being within normal (other than the vacuum fluctuation during throttle) I started double checking the ignition again. The book says to expect a primary resistance of 0.6-1.3 ohms between pins 1/2 and 2/4 (if you're looking at the coil's 4-pin connector from the passenger side, pinout is right to left; pin 1 being closest to the radiator, pin 4 being closest to the airbox). My coil reads 'open' (oL) at both these connections!?!
But now I'm ultra confused because my neighbor's coil had the same readings and my engine ran the same with his coil swapped in.

I also did what Nipper suggested which was disconnect each plug wire one at a time and note any fluctuation in idle. Cylinders 1, 2, 3, when pulled made the engine run rough(er) than normal. Cylinder 4 made no change in engine idle. Also, the spark coming from the boot of the other three wires was MUCH stronger. I'm talkin' a 1" spark though air between the boot and a ground. Cylinder 4, in order to see the spark I had to physically touch the tip of the boot to ground, even then it was weak. Also, the spark would miss every few revolutions.

...coil?

Edited by 211, 08 June 2009 - 06:18 PM.


#25 subsince77

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Posted 08 June 2009 - 08:42 PM

:popcorn::popcorn::popcorn:




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