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-   -   Cylinder misfire CEL (http://legacygt.com/forums/showthread.php?t=81165)

canis 02-10-2008 11:57 AM

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?).

rao 02-10-2008 12:06 PM

Injectors.

BoOCh_00_GT_Ltd 02-11-2008 12:34 PM

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?

canis 02-11-2008 12:40 PM

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.

ehsnils 02-11-2008 12:48 PM

Quote:

Originally Posted by canis (Post 1700190)
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?

BoOCh_00_GT_Ltd 02-12-2008 12:39 PM

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.

canis 02-12-2008 06:58 PM

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!

canis 02-15-2008 04:14 PM

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!

mbshop 02-15-2008 05:47 PM

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

canis 02-21-2008 03:29 PM

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?"

ehsnils 02-22-2008 11:41 AM

Quote:

Originally Posted by canis (Post 1723350)
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.

strikethree 02-23-2008 01:39 AM

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


Quote:

Originally Posted by canis (Post 1698621)
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?).


strikethree 02-23-2008 01:42 AM

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


Quote:

Originally Posted by canis (Post 1700190)
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.


strikethree 02-23-2008 01:51 AM

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


Quote:

Originally Posted by canis (Post 1723350)
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?"


canis 02-27-2008 11:14 AM

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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