Misfiring Outback

[stephenbybee]

I have a 98 Legacy Outback with a 2.5L engine and about 167,000 miles. A month ago the check engine light came on for the first time (ever) and I noticed that it was starting to run rough and the mileage wasn't so great. I first had a CarX mechanic check it out and he hooked it up to the computer and diagnosed the problem as "multiple misfire in cylinder #2". The plugs were only two months old, so I replaced the wires at this mechanic's suggestion and the problem did not go away. So I brought it back and his second suggestion was to replace the ECM. Knowing that this was a pricey fix I took it to the local Subaru dealer (Sommer's) and had them diagnose the problem. They also said that the #2 cylinder was misfiring. Their suggestion for repair was a new head assembly...about $1700. After this experience, I took my car to a local independent Subaru mechanic, Miles Fox, and he doesn't think that it could be a head problem because there is no smoke, no oil leakage, no oil in the water. He then took a look at the #2 fuel injector and found that when he unplugged it the car's idle changed, thus suggesting that the injector is working fine, but that it might be getting a bad signal from the ECM either due to a bad ground on ECM board, or a bad ECM that needs to be replaced. Is there anyone out there who thinks replacing the ECM might fix this problem??? Any suggestions??? I have taken very good care of this car and have had the timing belt, fuel pump, oil pump, and alternator replaced over the last four years, change the oil regularly, and flush and fill the tranny and radiator every year. Very rarely do I drive it over 70mph, and most of its miles lately are between 50-65 mph. Help me out, if you have any ideas. I love this car and don't want to give it up. Thanks.

[hankosolder2]

Well, it is hard to second-guess people who have actually looked at the vehicle, and I'm hardly an expert, but I think doing a compression test on the number 2 cylinder with the engine fully warmed up would be a good starting point. If the valve clearance has become too tight, it could cause missing once the engine is warmed up. Perhaps this relates to the Subaru dealer suggesting a head assembly (if they suspect a burned valve due to overly tight valve clearance.)

I would be interested to know WHEN the misfire occurrs, and if it is intermittent. Someone who knows more than me may correct me on this, but I think the injectors on this car might be "batch fired" (meaning that two injectors squirt fuel at the same time and the two pairs alternate.) If that is the case, it is unlikely that it is the ECM, as the paired injectors would be wired in parallel and any problem in the ECM would take out two cylinders at once. I could be wrong about this though...and it's also possible the ECM has current limiting resistors inside it for each injector, even if it is batch fired. You would have to look at a wiring diagram and see if each injector is individually wired back to the ECM or not.

 

If it is the ECM, you can probably find a used, junkyard ECM inexpensively and it shouldn't be that hard to replace. Do a search on car-part.com and see if anything comes up.

 

cheers,

Nathan

 

 

I have a 98 Legacy Outback with a 2.5L engine and about 167,000 miles. A month ago the check engine light came on for the first time (ever) and I noticed that it was starting to run rough and the mileage wasn't so great. I first had a CarX mechanic check it out and he hooked it up to the computer and diagnosed the problem as "multiple misfire in cylinder #2". The plugs were only two months old, so I replaced the wires at this mechanic's suggestion and the problem did not go away. So I brought it back and his second suggestion was to replace the ECM. Knowing that this was a pricey fix I took it to the local Subaru dealer (Sommer's) and had them diagnose the problem. They also said that the #2 cylinder was misfiring. Their suggestion for repair was a new head assembly...about $1700. After this experience, I took my car to a local independent Subaru mechanic, Miles Fox, and he doesn't think that it could be a head problem because there is no smoke, no oil leakage, no oil in the water. He then took a look at the #2 fuel injector and found that when he unplugged it the car's idle changed, thus suggesting that the injector is working fine, but that it might be getting a bad signal from the ECM either due to a bad ground on ECM board, or a bad ECM that needs to be replaced. Is there anyone out there who thinks replacing the ECM might fix this problem??? Any suggestions??? I have taken very good care of this car and have had the timing belt, fuel pump, oil pump, and alternator replaced over the last four years, change the oil regularly, and flush and fill the tranny and radiator every year. Very rarely do I drive it over 70mph, and most of its miles lately are between 50-65 mph. Help me out, if you have any ideas. I love this car and don't want to give it up. Thanks.

[FSRBIKER]

I have an ECM from a 97 Outback(5 speed) you can have for $25 + shipping.

[tcspeer]

I replaced the E.C.M. on my Legacy and it fixed a # 3 misfire, but it is very easy to check with a noid light. You can get a set for around 20.00 dollars from most auto stores. If the signal is coming from E.C. M. it will flash.

I have a 98 Legacy Outback with a 2.5L engine and about 167,000 miles. A month ago the check engine light came on for the first time (ever) and I noticed that it was starting to run rough and the mileage wasn't so great. I first had a CarX mechanic check it out and he hooked it up to the computer and diagnosed the problem as "multiple misfire in cylinder #2". The plugs were only two months old, so I replaced the wires at this mechanic's suggestion and the problem did not go away. So I brought it back and his second suggestion was to replace the ECM. Knowing that this was a pricey fix I took it to the local Subaru dealer (Sommer's) and had them diagnose the problem. They also said that the #2 cylinder was misfiring. Their suggestion for repair was a new head assembly...about $1700. After this experience, I took my car to a local independent Subaru mechanic, Miles Fox, and he doesn't think that it could be a head problem because there is no smoke, no oil leakage, no oil in the water. He then took a look at the #2 fuel injector and found that when he unplugged it the car's idle changed, thus suggesting that the injector is working fine, but that it might be getting a bad signal from the ECM either due to a bad ground on ECM board, or a bad ECM that needs to be replaced. Is there anyone out there who thinks replacing the ECM might fix this problem??? Any suggestions??? I have taken very good care of this car and have had the timing belt, fuel pump, oil pump, and alternator replaced over the last four years, change the oil regularly, and flush and fill the tranny and radiator every year. Very rarely do I drive it over 70mph, and most of its miles lately are between 50-65 mph. Help me out, if you have any ideas. I love this car and don't want to give it up. Thanks.

[tcspeer]

No more than a spark plug costs why dont you try a new one in that cyclinder. Also cheaper then trying a new E.C.M. is to take the coil pack off and have Auto Zone check it for free.

[Cougar]

I doubt that this problem is caused by the ECU. There may be a problem with the ignitor. I would first suggest using the Seafoam flush trick to try and clean out the carbon buildup in the engine. This has worked well for folks and may be all you need to do to fix this problem.

[idosubaru]

if they are not subaru OEM spark plug wires, then get another set. i've seen brand new off-the-shelf spark plug wires from auto parts stores cause cylinder mis-fire codes exactly as you say. the newer EJ motors like you have are not forgiving at all. stick with OEM Subaru only spark plug wires.

 

you can attempt to test this by swapping ignition wires around. clear the code, then swap the bad #2 ignition wire with your #1 cylinder. if the code comes up next as a #1 cyilnder misfire then you definitely isolated the wire as the cause.

even if it stays at #2 though it could still be wire related but much less likely.

 

i'd swap in a coil pack before an ECM. both can be had cheaply on here or at a junk yard. call and search around, i was looking for an EA82 ECM and saw the prices range from $35 - $609 for USED ones. i took the $35 route.

[bigfoot]

Make sure you're plugs are NGK OEM. I put Bosch in mine and it did the same thing your's is doing. I put the OEM plugs in and it runs like a top. Try the obvious easy cheap fix before going on. Also make sure you're running premium gas. It makes a huge difference in the 2.5 litre.

[stephenbybee]

Make sure you're plugs are NGK OEM. I put Bosch in mine and it did the same thing your's is doing. I put the OEM plugs in and it runs like a top. Try the obvious easy cheap fix before going on. Also make sure you're running premium gas. It makes a huge difference in the 2.5 litre.

I am going to try this first, along with having the coil checked, and then go from there if the problem persists. Thanks! I didn't know my Subaru was this picky about its parts, but I'll do whatever it takes to make it happy.

[stephenbybee]

I doubt that this problem is caused by the ECU. There may be a problem with the ignitor. I would first suggest using the Seafoam flush trick to try and clean out the carbon buildup in the engine. This has worked well for folks and may be all you need to do to fix this problem.

I think I have done every other flush except this one...is it tricky to do??

[stephenbybee]

I have an ECM from a 97 Outback(5 speed) you can have for $25 + shipping.

I am going to try the seafoam flush trick, then check the coil pack and replace plugs and wires with the OEM variety. If none of these fixes do the trick, I am going to take you up on that offer. Will an ECM from a 5speed work alright on my automatic...is there even any difference?

[stephenbybee]

No more than a spark plug costs why dont you try a new one in that cyclinder. Also cheaper then trying a new E.C.M. is to take the coil pack off and have Auto Zone check it for free.

Thanks...I will do both of these and see if anything changes. I don't mind covering a few extra bases as long as it isn't too pricey (yet).

[FSRBIKER]

I am not sure, someone here should know though. I also have a few coil packs as well.

For what it's worth my Datsun 240Z's only ran on NGK's as well, and the older Mercedes motors I used to rebuild only on Bosch.

 

I am going to try the seafoam flush trick, then check the coil pack and replace plugs and wires with the OEM variety. If none of these fixes do the trick, I am going to take you up on that offer. Will an ECM from a 5speed work alright on my automatic...is there even any difference?