98 Forester mystery missfire codes.

[monkeyhawk71]

I'm at the end of my wits with a consistent missfire code on 3 & 4 on a 98 Forester. I have done plugs and wires, coil, top engine clean, injector clean. When the light flashes, then sets, I feel nothing, no missfire at all. It's usually on a fwy offramp or down a slight grade, not really into the throttle. The local dealer didn't give me a feeling of confidence after it sat there 3 days, pretty much went over what I had already done. They suggested a valve problem and want to pull the head and go from there, but are not willing to stand behing their guess. If they're wrong, I still pay. Am I missing something or are they on the right path? I surely appreciate any advise.

[TheBrian]

Shot in the dark: If you have an overkill stereo system, it can misfire when bass hits coincide with low alternator RPMs.

 

Even if you don't have a 5kW sound system, I'd consider replacing the battery if the battery is marginal.

 

Or just live with it. Don't pull the head.

[monkeyhawk71]

Nothing non-stock except a Bazooka 8", usually talk radio (like that needs bass), but it only takes a second to unhook it, so I'll try it. Thanks.

Shot in the dark: If you have an overkill stereo system, it can misfire when bass hits coincide with low alternator RPMs.

 

Even if you don't have a 5kW sound system, I'd consider replacing the battery if the battery is marginal.

 

Or just live with it. Don't pull the head.

[Downbound]

Get them to do a compression test on 3 & 4 before they pull the heads..

I'm at the end of my wits with a consistent missfire code on 3 & 4 on a 98 Forester. I have done plugs and wires, coil, top engine clean, injector clean. When the light flashes, then sets, I feel nothing, no missfire at all. It's usually on a fwy offramp or down a slight grade, not really into the throttle. The local dealer didn't give me a feeling of confidence after it sat there 3 days, pretty much went over what I had already done. They suggested a valve problem and want to pull the head and go from there, but are not willing to stand behing their guess. If they're wrong, I still pay. Am I missing something or are they on the right path? I surely appreciate any advise.

[color-blind]

I'm at the end of my wits with a consistent missfire code on 3 & 4 on a 98 Forester. I have done plugs and wires, coil, top engine clean, injector clean. When the light flashes, then sets, I feel nothing, no missfire at all. It's usually on a fwy offramp or down a slight grade, not really into the throttle. The local dealer didn't give me a feeling of confidence after it sat there 3 days, pretty much went over what I had already done. They suggested a valve problem and want to pull the head and go from there, but are not willing to stand behing their guess. If they're wrong, I still pay. Am I missing something or are they on the right path? I surely appreciate any advise.

 

Is your Forester a 5-spd model? If it is, was the clutch replaced recently?

[monkeyhawk71]

Why, as a matter of fact, it was. Not long before this all started, I just never imagined they'd be related. Please elaborate. Thanks.

Is your Forester a 5-spd model? If it is, was the clutch replaced recently?

[color-blind]

Why, as a matter of fact, it was. Not long before this all started, I just never imagined they'd be related. Please elaborate. Thanks.

 

The ecu monitors for misfires thru the cam and crank sensors. If their is a problem with thier relationship it sets mis-fire codes. This is a difficult diagnosis to determine; you should also check the valve clearances on the cylinders that have the mis-fires. If valve clearance is good then do the following; replace the clutch assembly with oe parts and install a new oe flywheel. Subaru will have all these parts in stock. Basically you are having a balance issue. Been their done that. Good luck.

[monkeyhawk71]

When we had my transmission out for a leak, we replaced everything with oem from the dealer. Could the flywheel just be out of balance?

The ecu monitors for misfires thru the cam and crank sensors. If their is a problem with thier relationship it sets mis-fire codes. This is a difficult diagnosis to determine; you should also check the valve clearances on the cylinders that have the mis-fires. If valve clearance is good then do the following; replace the clutch assembly with oe parts and install a new oe flywheel. Subaru will have all these parts in stock. Basically you are having a balance issue. Been their done that. Good luck.

[color-blind]

When we had my transmission out for a leak, we replaced everything with oem from the dealer. Could the flywheel just be out of balance?

 

First off, make sure 100% that the parts we're purchased from a dealer. I've seen many shops claim to use oe parts; then to find out later they we're aftermarket. Did you do this job yourself? If not then I would want to see a receipt from the dealer on the parts.

 

What was done to the flywheel? Was it surfaced or just "whizzy" wheeled clean? This balance issue is very hard to confirm. If the flywheel was turned; and oe parts we're installed I would install an oe flywheel. Subaru does not recommend flywheel surfacing. I know a lot of shops and dealers do it. Basically the mis-fire monitor on the phase one 2.5 is too sensitive. Good luck.

 

Color-blind

20 year Subaru tech

[monkeyhawk71]

I'm a service writer at a Chevy dealer and bought everything myself so I know that's ok. But, I think I could get them to do a parts warranty on the flywheel. It makes sense. Your advice might just save my sanity. Thanks again. sb

First off, make sure 100% that the parts we're purchased from a dealer. I've seen many shops claim to use oe parts; then to find out later they we're aftermarket. Did you do this job yourself? If not then I would want to see a receipt from the dealer on the parts.

 

What was done to the flywheel? Was it surfaced or just "whizzy" wheeled clean? This balance issue is very hard to confirm. If the flywheel was turned; and oe parts we're installed I would install an oe flywheel. Subaru does not recommend flywheel surfacing. I know a lot of shops and dealers do it. Basically the mis-fire monitor on the phase one 2.5 is too sensitive. Good luck.

 

Color-blind

20 year Subaru tech

[color-blind]

I'm a service writer at a Chevy dealer and bought everything myself so I know that's ok. But, I think I could get them to do a parts warranty on the flywheel. It makes sense. Your advice might just save my sanity. Thanks again. sb

 

What did they do with the flywheel?

 

Surface it or replace it?

 

Chances are they will not have heard of this before. Don't be surprised if they think your a little crazy. Good luck.

[monkeyhawk71]

Yep, they resurfaced it. I oredered a new one today. Nobody at Subaru, service or parts, has ever heard of this. I did some research after you brought it up and I now know I'm not alone. I should start a support group or something. I'm just happy to finally be driving it after 4 years of making payments on it. It's been my wife's driver and she never really liked it. We just got her a new Suzuki Forenza (sorry but it's the most car for the money) and now the Forester is mine.....all mine!! My 72 Datsun 510 isn't too fun on the Oregon roads on dark winter nights, so it gets to hibernate now.

What did they do with the flywheel?

 

Surface it or replace it?

 

Chances are they will not have heard of this before. Don't be surprised if they think your a little crazy. Good luck.