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Cylinder misfire CEL


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Hello all. 2005 Legacy GT, 50k miles, no mods. I got a check engine light for cylinder misfires on 1, 3, and 4. I brought it to the dealer, and they said I had two bad ignition coil packs. I replaced all four coils, all four spark plugs (see pic), and got a new battery. The next day, I got a CEL for cylinder misfires on 1, 3, and 4. Any idea what else it could be?

 

Regarding the plugs - three are almost identical looking, and I don't remember where each was from. The black plug was from the driver's front cylinder (#1?).

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It's done it through more than one tank of gas (different brands) and a bottle of Lucas injector cleaner. No real noticeable symptoms. Just a slight, erratic tick in the idle, but I may be dreaming things. Overall the car drives fairly normal. The most consistent thing about when the light comes on is when its below 50*. The spark plugs I pulled out (in the pic) only have about 7k on them. I just replaced them last spring.
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It's done it through more than one tank of gas (different brands) and a bottle of Lucas injector cleaner. No real noticeable symptoms. Just a slight, erratic tick in the idle, but I may be dreaming things. Overall the car drives fairly normal. The most consistent thing about when the light comes on is when its below 50*. The spark plugs I pulled out (in the pic) only have about 7k on them. I just replaced them last spring.

 

Just check if the single spark plug is consistently getting extra soot or if it's a temporary problem. It may be temporary due to Murphy's law, but it may also indicate that there is a small oil leak or a faulty injector in that cylinder.

 

Just a curious question? Why so many different threads on the same subject?

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if it only does it when the engine is below 50 degrees, i would think that there is a problem with the coolant temperature sensor for the computer. but does it set the light immediately when ambient temp is under 50 and coolant temp is inder 50, or will it set the light if the engnie temperature is warm and the ambient temp is under 50? if it is the later there may be an issue wiht the ambient / intake air temperature sensor. then agian weak fuel pressure can cause issues with colder temperatures since it requires more fuel to run an engine in the cold.
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Well the car has been at the dealer for two days now. They can't figure it out, and have enlisted the help of the Subaru Tech Line.

 

The light does not immediately come on at a certain temperature. It will either come on after idling for a couple minutes, or in the middle of leisurely driving. In one case, the coolant is cold, in the other it's hot.

 

I will check the #1 cylinder plug when I get the car back. Regarding the multiple posts...when ever there is a noteworthy update (a new starting-off point, per se), it seems more convenient for others if I create a new post with a nice, short summary right up front summing up all the previous conclusions so that new observers and those (like yourself) offering assistance may get to the point quickly, without having to read through several back-and-forths.

 

Thanks again all!

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Errrrrr...Dealer has had car since Monday. No clue what's wrong. They've ordered an air/fuel ratio sensor to see what that does. They said they checked the injectors and the fuel line pressure. I suggested they probably checked the pressure when it was in the warm shop, so they're going to check it again outside early one cold morning next week. In the mean time, still no Subie for me!
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kinda amazed that they can't figure it out as the computer should be able to zero in on it rather easily. might suggest using a dual trace lab scope and have them check things that way. you will get yer money back, right?

 

george

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Dealer still has my car. After speaking with the tech line, they say it's the pre-cat air/fuel ratio sensor (O2 sensor), which they've ordered. If the car had a bad O2 sensor, isn't the computer sophisticated enough to say "you have a bad O2 sensor?"
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If the car had a bad O2 sensor, isn't the computer sophisticated enough to say "you have a bad O2 sensor?"

 

Not necessarily - it depends on HOW it is bad. It may be sending a signal that is within the acceptable limits and therefore the computer doesn't detect it as bad. The detection is usually a check if the sensor transmits a voltage outside the range.

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The plugs look fine at first glance but a higher resolution image may show something different. The cylinder the "black" plug came from is definitely too rich but it is not that bad. Hm, the other ones look like they may be running hot. Can you provide a picture with better focus and more detail?

 

strike

 

 

Hello all. 2005 Legacy GT, 50k miles, no mods. I got a check engine light for cylinder misfires on 1, 3, and 4. I brought it to the dealer, and they said I had two bad ignition coil packs. I replaced all four coils, all four spark plugs (see pic), and got a new battery. The next day, I got a CEL for cylinder misfires on 1, 3, and 4. Any idea what else it could be?

 

Regarding the plugs - three are almost identical looking, and I don't remember where each was from. The black plug was from the driver's front cylinder (#1?).

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Do you have, or know someone who has, a Tactrix cable? Seeing a data log would be invaluable. Are there any bright metallic specks on the plugs? Your picture is not good enough to verify.

 

strike

 

 

It's done it through more than one tank of gas (different brands) and a bottle of Lucas injector cleaner. No real noticeable symptoms. Just a slight, erratic tick in the idle, but I may be dreaming things. Overall the car drives fairly normal. The most consistent thing about when the light comes on is when its below 50*. The spark plugs I pulled out (in the pic) only have about 7k on them. I just replaced them last spring.
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The O2 sensor may be bad, however, your plugs should not look like that. I have seen thousands of plugs (most of them from my over-modded Talon) and they should all have the same (roughly) amount of carbon on them. For my Talon, Cylinder one has the most amount of carbon and cylinder 4 has the least but it is a smooth progression and they look roughly the same. Your engine is obviously different, but the same rules apply.

 

Tell me if I am correct with this: The plug with the most carbon is the one cylinder that has no misfires.

 

Yes? No?

 

If you have a friend with wideband (high quality, high accuracy AFR meter) have them do some datalogging with it. Also, as I said earlier, some data logs from the ECU would be invaluable.

 

strike

 

 

Dealer still has my car. After speaking with the tech line, they say it's the pre-cat air/fuel ratio sensor (O2 sensor), which they've ordered. If the car had a bad O2 sensor, isn't the computer sophisticated enough to say "you have a bad O2 sensor?"
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They've had my car for over two weeks now. They put in a new O2 sensor, but that was not the problem. There's three mechanics on it now, plus Tech Line, all scratching their heads. The next step is to order a new ECM, because the current one is telling cylinders 1 & 3 to run rich, and something is overcompensating for something else and blah blah blah. At least that part is covered under warranty. So I'm picking up the car, since it'll be another week before the ECM gets here.

 

The plug with the most carbon is the driver's side plug at the front of the car. Cylinder two has no misfires. I don't know if these are the same or not.

 

Don't know anyone with Tactrix cable or that can datalog. Don't have my car either :-(. I'll try to get a better pic of the plugs.

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Well they got the new ECM in yesterday. But the mechanic hadn't charged the battery of their Subaru laptop, and it was totally dead and couldn't complete the programming of the new ECM. So they had to get a new battery, which had to charge overnight. As of this morning, they said it's a bad new ECM (they can't get it to program), so they're having to order a new new one. They are sending a shuttle to get me and bring me to pick up a rental car (which they're paying for). I'm hoping now that it's costing them money to figure this out and get my car fixed, it'll speed up the process (which began over a month ago).
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Have any of them checked for cracked valves? I had exactly the same problem on my '00 at 90k...CEL while cold or while driving, black plug. I had a pie sliced valve (split from the outer edge inward). Even the dealer couldn't figure out why it wouldn't happen right off when cold.

 

Hope you get it figured out....

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I doubt it. When I picked up the rental car, I stopped by the dealership. I bypassed the service counter and went in the back door to speak directly to the mechanic. Coming back to RAO's statement, he thinks its the injectors, so he has three on order and being overnighted. Fingers crossed and we'll know tomorrow! If that's not it, I'll suggest cracked valves.
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Well I've had my car back for about a week now with the new injectors. I think this might be the answer! The car idles noticeably smoother (I hadn't realized the idle was bad - I thought it was a boxer thing), and is all-round more lively. I just reinstalled the Accessport last night, and I now remember why I love this car so much!
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possubly moisture in your gas, vacccum leak, weak fuel pressure. any other symptoms besides the light? can u get pic of the new plugs? there are many things that can cause multiple missfires. do you have any other symptoms to help us, or a description of when the car runs bad?

+1. You can have a bad injector, something in the valve train causing it(I.E bad valve, dirty valve,etc), sometimes caused by injectors, incorrect spark plugs(some people put in ones that are too short and get a misfire and then it kills the coil), the coil itself.

 

OP- Hope everything works out and the car is fixed.

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  • 3 weeks later...
I just called around.. Subaru wants anywhere from 100-140 for an injector.. depends on the dealer around here. I am going to swap the cylinder 2 and 4 injectors just to check and see if the code changes to make sure its the injector first. I am going to have to order the injector anyways cause nobody has one in stock. I switched the coil packs and spark plugs yesterday and I still have the cyl 4 misfire. So I will try the injector next, I really hope that its just my injector thats bad instead of who knows what else...
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