Help with P0304 piston misfire?
07-05-2004, 08:26 AM
#1
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Car Info: 2005 Legacy GT Ltd, 2001 Outback LL Bean
Help with P0304 piston misfire?
Greetin's. 
Well I've tried this on NASIOC, and gotten lots of suggestions from them, and lots of struggling from dealerships. Here's the skinny:
I have a P0304 piston misfire CEL. It's been happening for 6-7k now, since I'd say this past January or so. (My car has just over 106k miles on it, right now.) Initially, the dealership (Exeter Subaru in Stratham, NH--I lived near there up until Feb. of this year, I'm in PA now) thought it was old plugs and/or wires. I hadn't changed those in about 30k, so I bought them and went to do the swap. Pulled the wire off plug #1 and found oil in the chamber. Brought it to the dealership.
Exeter did the plug/wire change there, and replaced the gaskets/seals that were leaking. Cleared the CEL, but it came back. They cleared it a couple more times, agonized over the possible cause, and sent me home with the car. Light kept coming back. It would stay on steadily sometimes for days, sometimes would go away after 2-3 trips, and return similarly.
Eventually they suggested replacing the ignition coil, so I permitted them to. That didn't work. They suggested a compression and leakdown test, so I did that as well. They came back clean, no problems. I had them also do a full fuel injection cleaning service.
Long story short(er), while I appreciated what help they offered, it was more of a "anxious to arbitrarily suggest expensive fixes" rather than make an effort to figure out possible causes first, THEN start replacing things. I opened a case with SoA, but got very little help. I do know they called Exeter and asked for faxed copies of all the service records, which ticked off the service manager. (Exeter's Parts Department and actual technicians have a great reputation. The Sales and Service Counter guys were positively awful, however. Unfortunately, they're who you deal with.)
At that point I got fed up with giving them money, receiving no help from neither them nor SoA in the way of intelligent ideas as to what causes this thing. My wife and I moved to PA in February, and the problem still exists. The car runs fine, it always has. No symptoms. I'm at a standstill, right now. I REALLY need ideas.
I took home a copy of a recent "The End Wrench" magazine, where in the end it suggests that phase II EJ25 powerplants sometimes have slight piston misfires if the fuel filter was recently replaced. Along the same thinking, I figured maybe an old filter might cause it. So I ordered one and replaced it a few days ago. Sadly, the light still exists. One person suggested a valve adjustment, but I've heard from others (including one dealership) that you don't NEED to adjust the valves on this car. That any dealership who does it, is ripping you off. (My original dealer did it on my 30k service, but I don't remember if I did it on my 60k. I think the latter involved the dealership who said "you don't need it.")
I've heard several ideas, but nothing definitive. I know it's a trial-and-error thing sometimes, but I can't be the only one who hasn't been able to figure this out.
One other idea is stuck valve sliders and/or a failing head. But then most people say it's usually an electrical thing, which is why the coilpacks are replaced. I just don't know.
Please give me some ideas.
I refuse to pay a dealership a couple/few hundred more dollars just to tinker. I need some intelligence, here! SoA hasn't even answered calls or Emails in over three months; all I asked from them was the same thing. Tech advice on what components may be contributing. All I got was a generic "We'll help pay for the next diagnosis." What's that mean? Pulling the code? Great, well, AutoZone does that for free.
*sigh*
Thanks-
=S2=
2000 Impreza 2.5RS (manual)
Well I've tried this on NASIOC, and gotten lots of suggestions from them, and lots of struggling from dealerships. Here's the skinny:
I have a P0304 piston misfire CEL. It's been happening for 6-7k now, since I'd say this past January or so. (My car has just over 106k miles on it, right now.) Initially, the dealership (Exeter Subaru in Stratham, NH--I lived near there up until Feb. of this year, I'm in PA now) thought it was old plugs and/or wires. I hadn't changed those in about 30k, so I bought them and went to do the swap. Pulled the wire off plug #1 and found oil in the chamber. Brought it to the dealership.
Exeter did the plug/wire change there, and replaced the gaskets/seals that were leaking. Cleared the CEL, but it came back. They cleared it a couple more times, agonized over the possible cause, and sent me home with the car. Light kept coming back. It would stay on steadily sometimes for days, sometimes would go away after 2-3 trips, and return similarly.
Eventually they suggested replacing the ignition coil, so I permitted them to. That didn't work. They suggested a compression and leakdown test, so I did that as well. They came back clean, no problems. I had them also do a full fuel injection cleaning service.
Long story short(er), while I appreciated what help they offered, it was more of a "anxious to arbitrarily suggest expensive fixes" rather than make an effort to figure out possible causes first, THEN start replacing things. I opened a case with SoA, but got very little help. I do know they called Exeter and asked for faxed copies of all the service records, which ticked off the service manager. (Exeter's Parts Department and actual technicians have a great reputation. The Sales and Service Counter guys were positively awful, however. Unfortunately, they're who you deal with.)
At that point I got fed up with giving them money, receiving no help from neither them nor SoA in the way of intelligent ideas as to what causes this thing. My wife and I moved to PA in February, and the problem still exists. The car runs fine, it always has. No symptoms. I'm at a standstill, right now. I REALLY need ideas.
I took home a copy of a recent "The End Wrench" magazine, where in the end it suggests that phase II EJ25 powerplants sometimes have slight piston misfires if the fuel filter was recently replaced. Along the same thinking, I figured maybe an old filter might cause it. So I ordered one and replaced it a few days ago. Sadly, the light still exists. One person suggested a valve adjustment, but I've heard from others (including one dealership) that you don't NEED to adjust the valves on this car. That any dealership who does it, is ripping you off. (My original dealer did it on my 30k service, but I don't remember if I did it on my 60k. I think the latter involved the dealership who said "you don't need it.")
I've heard several ideas, but nothing definitive. I know it's a trial-and-error thing sometimes, but I can't be the only one who hasn't been able to figure this out.
One other idea is stuck valve sliders and/or a failing head. But then most people say it's usually an electrical thing, which is why the coilpacks are replaced. I just don't know.
Please give me some ideas.
I refuse to pay a dealership a couple/few hundred more dollars just to tinker. I need some intelligence, here! SoA hasn't even answered calls or Emails in over three months; all I asked from them was the same thing. Tech advice on what components may be contributing. All I got was a generic "We'll help pay for the next diagnosis." What's that mean? Pulling the code? Great, well, AutoZone does that for free.*sigh*
Thanks-
=S2=
2000 Impreza 2.5RS (manual)
Last edited by Siper2; 07-05-2004 at 08:30 AM.
07-05-2004, 08:36 AM
#2
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Location: Dillsburg, PA
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Car Info: 2005 Legacy GT Ltd, 2001 Outback LL Bean
Ecu & CAI
I just read this:
https://www.i-club.com/forums/suby-shopping-maintenance-warranty-92/02-wrx-cylinder-misfire-p0304-56966/
(At the bottom of my thread as a "suggested" similar topic.)
One fellow did indeed suggest that the code might be bad. I'd had the ECU reprogrammed by SoA a couple of years ago, after they'd paid to replace five blown O2 sensors on my car, as a result of the Parts Recall #WXW80.
My car wasn't in the original VIN range for the reflash, but I guess they thought it was a better, proactive approach, rather than paying for a bunch of O2 sensors every 10k miles. To date, I haven't blown another one.
However, there was at least a year in between the reflash and the first occurrence of the P0304. So, would that make sense as a coincidence?
Also, I read the "denial of warrantee" thread as well (https://www.i-club.com/forums/suby-shopping-maintenance-warranty-92/misfire-errors-denial-warranty-54942/). I do have a PDM-Racing CAI, which utilizes the stock airbox (similar to GanzFlow). After the plug/wire swap but before the coilpack I believe, the tech came and asked me to replace it with the OEM one, just as a troubleshooting step. (That one tech was very helpful.)
I did, and needless to say it didn't work. CAI is now back on the car, I put it back on about a month ago.
=S2=
https://www.i-club.com/forums/suby-shopping-maintenance-warranty-92/02-wrx-cylinder-misfire-p0304-56966/
(At the bottom of my thread as a "suggested" similar topic.)
One fellow did indeed suggest that the code might be bad. I'd had the ECU reprogrammed by SoA a couple of years ago, after they'd paid to replace five blown O2 sensors on my car, as a result of the Parts Recall #WXW80.
My car wasn't in the original VIN range for the reflash, but I guess they thought it was a better, proactive approach, rather than paying for a bunch of O2 sensors every 10k miles. To date, I haven't blown another one.
However, there was at least a year in between the reflash and the first occurrence of the P0304. So, would that make sense as a coincidence?
Also, I read the "denial of warrantee" thread as well (https://www.i-club.com/forums/suby-shopping-maintenance-warranty-92/misfire-errors-denial-warranty-54942/). I do have a PDM-Racing CAI, which utilizes the stock airbox (similar to GanzFlow). After the plug/wire swap but before the coilpack I believe, the tech came and asked me to replace it with the OEM one, just as a troubleshooting step. (That one tech was very helpful.)
I did, and needless to say it didn't work. CAI is now back on the car, I put it back on about a month ago.
=S2=
Last edited by Siper2; 07-05-2004 at 08:43 AM.
07-14-2004, 02:38 PM
#4
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Originally Posted by Siper2
ttt
Please help!
Please help!
And the o2 sensors should have been replaced by now anyways.
Btw the code indicates cylinder #4 as the problem.
07-14-2004, 02:43 PM
#5
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Is that a question?
Yes, it's #4. The P030x just designates the misfire. The last digit (in my case, a P0304) states it's cylinder 4.
Plugs were replaced, as you read, and the O2 sensor several times (under Parts Recall #WXW80, followed by the ECU reflash).
Yes, it's #4. The P030x just designates the misfire. The last digit (in my case, a P0304) states it's cylinder 4.
Plugs were replaced, as you read, and the O2 sensor several times (under Parts Recall #WXW80, followed by the ECU reflash).
07-14-2004, 03:12 PM
#6
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Car Info: Mazda Protege '02 (Wishing protege has AWD and a H6 twin turbo)
Originally Posted by Siper2
Is that a question?
Yes, it's #4. The P030x just designates the misfire. The last digit (in my case, a P0304) states it's cylinder 4.
Plugs were replaced, as you read, and the O2 sensor several times (under Parts Recall #WXW80, followed by the ECU reflash).
Yes, it's #4. The P030x just designates the misfire. The last digit (in my case, a P0304) states it's cylinder 4.
Plugs were replaced, as you read, and the O2 sensor several times (under Parts Recall #WXW80, followed by the ECU reflash).
I guess a couple things could happen. You could be running a lil too lean and creating the problem. Perhaps a fuel system cleaner?
And if you could get it done a compression test
07-14-2004, 05:16 PM
#7
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Car Info: 95 Impreza coup, green, 5speed 1.8l awd
just to let you know the 97 and newer cars all have solid valve lifters unlike all subys before 97 that had hydrolic lifters what this means is that at 100k miles solid lifter do need to be adjusted and hydrolic lifters are self adjusting
does the car seem down on power? because if not i bet that there is nothing physicly wrong with the car and a sensor malfunction is the cause
does the car seem down on power? because if not i bet that there is nothing physicly wrong with the car and a sensor malfunction is the cause
07-14-2004, 06:13 PM
#8
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Well, how much "down on power" would it be? If it's just a little, I might not notice. Really I haven't noticed anything different, so that's why I ask.
I will definitely schedule a valve adjustment if it needs it, though.
RoadSpike,
Had the compression test done. I mentioned that in my first post, too.
(Or if I didn't, I meant to. Compression and leakdown tests were both done, as well as a full fuel injection cleaner service. This was all about, enh, 10k miles ago, maybe less. The tests came back clean/good/whatever. No problems with those, essentially.)
I will definitely schedule a valve adjustment if it needs it, though.
RoadSpike,
Had the compression test done. I mentioned that in my first post, too.
(Or if I didn't, I meant to. Compression and leakdown tests were both done, as well as a full fuel injection cleaner service. This was all about, enh, 10k miles ago, maybe less. The tests came back clean/good/whatever. No problems with those, essentially.)
08-06-2004, 07:24 AM
#9
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I've had the some problem for a few months now, same P0304 code. I have serious misfires going on, and it is really evident at in 1st and 2nd gears shortly after starting the car. I get a lot of hesitation and can definately feel the misfire. Sometimes though the CEL goes away for a few days, and then on my way to work I'll pull away from a stop sign or stop light, and feel severe hesitation and the CEL will pop on.
The dealer doesn't know what to do, they looked at my plugs and coil packs and said there was nothing wrong there. I am not spending money for someone to trial and error troubleshoot my car, so any info here would be most helpful.
The dealer doesn't know what to do, they looked at my plugs and coil packs and said there was nothing wrong there. I am not spending money for someone to trial and error troubleshoot my car, so any info here would be most helpful.
08-06-2004, 09:57 AM
#10
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Originally Posted by Siper2
RoadSpike,
Had the compression test done. I mentioned that in my first post, too.
(Or if I didn't, I meant to. Compression and leakdown tests were both done, as well as a full fuel injection cleaner service. This was all about, enh, 10k miles ago, maybe less. The tests came back clean/good/whatever. No problems with those, essentially.)
Had the compression test done. I mentioned that in my first post, too.
(Or if I didn't, I meant to. Compression and leakdown tests were both done, as well as a full fuel injection cleaner service. This was all about, enh, 10k miles ago, maybe less. The tests came back clean/good/whatever. No problems with those, essentially.)
Ok yeah i'm a dufus and speed read everything.
Looks like you've taken alot of trouble shooting steps to insure that your car runs nominally.
The only thing i could think of was the fuel itself, such as small bits of water in the system or just bad fuel.
Do you run different gas?
08-09-2004, 12:37 AM
#11
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though unlikely(although you seem to have explored most if not all of your options) I've heard of cars (not subarus in particular, but nonetheless) with major carbon buildup, or depostis on the cylinders having hot-spots which could possibly cause a misfire. I am, of course, just guessing as you seem to have done alot to try to correct the problem, not to mention troubleshooting is always easier with access to the car...
10-05-2004, 03:41 PM
#12
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Bump.
Serious bump.
I'd forgotten about this thread. Sorry, guys....
Here's the deal. SoA has still been entirely useless. No exaggeration.
Long story short, I had the code pulled at a local dealership, and it was evident that the P0304 code was gone, now replaced by a "bad knock sensor" code. (I forget which, specifically.) That diagnostic was claimed to be reimbursed by SoA, but they've yet to even do that for me. I'm ready to go to Cherry Hill, NJ with a shovel and a smile, pretty soon...
Anyway, their price estimate for part + labor was absurd. So, I had Exeter Subaru in NH send me the part, and I installed it myself in about four minutes. (Some repair prices are reasonable; others make you want to strangle someone.....)
Guess what???
That was in like early August. I have YET to see the CEL return.
So here's what makes me curious: could it have been a failing knock sensor all along?!?!?!
Not sure how closely-tied "knock" and "misfire" can be, but it sort of makes sense....
Only sort of.
Serious bump.
I'd forgotten about this thread. Sorry, guys....
Here's the deal. SoA has still been entirely useless. No exaggeration.
Long story short, I had the code pulled at a local dealership, and it was evident that the P0304 code was gone, now replaced by a "bad knock sensor" code. (I forget which, specifically.) That diagnostic was claimed to be reimbursed by SoA, but they've yet to even do that for me. I'm ready to go to Cherry Hill, NJ with a shovel and a smile, pretty soon...
Anyway, their price estimate for part + labor was absurd. So, I had Exeter Subaru in NH send me the part, and I installed it myself in about four minutes. (Some repair prices are reasonable; others make you want to strangle someone.....)
Guess what???
That was in like early August. I have YET to see the CEL return.
So here's what makes me curious: could it have been a failing knock sensor all along?!?!?!
Not sure how closely-tied "knock" and "misfire" can be, but it sort of makes sense....
Only sort of.
10-05-2004, 04:04 PM
#13
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I forgot about this thread also.
Siper2, your dealership is correct. I had the same misfiring on cyl 3. Changed my plugs a few months ago but the CEL came back on and the plugs on 3 and 4 were corroded again. Ended up being a bad knock sensor. If the sensor detects a knock or goes bad, it changes timing. Apparently a bad sensor changes timing so much that it will seriously corrode the hell out of one bank, mine being the right bank. They replaced it for $230 parts and labor. I was kind of pissed because I specifically told them to call me before any parts were to be added but they didn't. The knock sensor is easy to replace, and the part only cost $125 according to them. I didn't say anything about it but I'm simply not going back there again at $51/hour labor. 2 hours to replace knock sensor? No way.
My car has run like a champ ever since. The engine feels and sounds completely different.
Siper2, your dealership is correct. I had the same misfiring on cyl 3. Changed my plugs a few months ago but the CEL came back on and the plugs on 3 and 4 were corroded again. Ended up being a bad knock sensor. If the sensor detects a knock or goes bad, it changes timing. Apparently a bad sensor changes timing so much that it will seriously corrode the hell out of one bank, mine being the right bank. They replaced it for $230 parts and labor. I was kind of pissed because I specifically told them to call me before any parts were to be added but they didn't. The knock sensor is easy to replace, and the part only cost $125 according to them. I didn't say anything about it but I'm simply not going back there again at $51/hour labor. 2 hours to replace knock sensor? No way.
My car has run like a champ ever since. The engine feels and sounds completely different.
10-06-2004, 03:45 PM
#14
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Well, my engine never felt or sounded funny at all.... which is what was weird.
I now have no doubt that that is what was causing the problem, all along. But for Exeter Subaru in NH to give me that runaround and never even consider the knock sensor? C'mon... I know shop manuals exist. I know they've got smart techs, I've met a couple of them.
They hosed me, plain and simple, and SoA probably doesn't care.
You definitely got ripped off on the install. The dealer here in PA wanted a shade over $100 for the sensor, and quoted $180ish total for parts plus labor. One thing Exeter's good for is Parts (North Ursalia is the counter guy there ), so I called them. They sell them for around $84, plus I got a NESIC discount, and no sales tax since it's NH.
Two hours labor??? MAKE ME LAUGH!!! I'm a total mechanical buffoon (though maybe I'm slowly climbing up the talent ladder... perhaps I'm to the second rung by now...) and did the whole thing in literally five minutes, once I'd researched the location and instructions on Scoobymods.
*sigh* Some labor rates really are acceptable. Others, like this, just ..... Damn.
I now have no doubt that that is what was causing the problem, all along. But for Exeter Subaru in NH to give me that runaround and never even consider the knock sensor? C'mon... I know shop manuals exist. I know they've got smart techs, I've met a couple of them.
They hosed me, plain and simple, and SoA probably doesn't care.
You definitely got ripped off on the install. The dealer here in PA wanted a shade over $100 for the sensor, and quoted $180ish total for parts plus labor. One thing Exeter's good for is Parts (North Ursalia is the counter guy there
), so I called them. They sell them for around $84, plus I got a NESIC discount, and no sales tax since it's NH. Two hours labor??? MAKE ME LAUGH!!!
I'm a total mechanical buffoon (though maybe I'm slowly climbing up the talent ladder... perhaps I'm to the second rung by now...) and did the whole thing in literally five minutes, once I'd researched the location and instructions on Scoobymods.*sigh* Some labor rates really are acceptable. Others, like this, just ..... Damn.
10-06-2004, 03:50 PM
#15
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I'm surprised your engine didn't feel funny. I had some serious stumbling and hesitation. I could definately feel the misfiring. I know I got completely ripped off. But I'm more upset that they didn't tell me they were doing it. I would have bought the part from them and did it myself.
Luckily, I found a shop locally here that was opened by an ex Subaru tech from that same dealership, and they charge $32/hr. I'm going to him from now on.
Dillsburg eh? Good friend of mine grew up there. You go to Northern? What graduating class?
Luckily, I found a shop locally here that was opened by an ex Subaru tech from that same dealership, and they charge $32/hr. I'm going to him from now on.
Dillsburg eh? Good friend of mine grew up there. You go to Northern? What graduating class?