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Engine rumbling at low rpm

Over the past 2 days My 98 Legacy AT with 2.2ltr engine has developed a low RPM rumbling. Not noticeable at IDLE but around 1000 - 1300 rpms it is very noticeable. I can hear it and feel it. Recently (3 weeks ago) the car's check engine light came on. The OBDII code was "misfire on cylinder 1 and misfire on cylinder 2) code 301 and 301 (if I remember correctly). I replaced the spark plugs (NGKs) and spark plug wires and reset the ECM with the scanner. Now 3 weeks later I have the low rumbling noise. The rumbling happens with the car in park or in neutral so I don't believe it is transmission related. The sound/feeling is difficult to describe and it is not a pinging but rather a lower vibrating knocking sound. The sensation was such that I even suspected motor mounts - but they are okay. The Check Engine light has remained off. I rechecked my plug & wires and all seems correct. My next step is to schedule an appointment at a shop but do any of you have suggestions on what I might be able to try?

Thanks,

Djay

Reply to
DJay
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Oh the car has 80K miles on it...

Reply to
DJay

Check groups.google.com for my frustrations with the same issue with

01 Outback. Mine only seemed to be an issue in warm months. I don't notice it anymore, perhaps I've just gotten used to it. Subaru checked it out several times and said "no problem found." I talked with a factory service rep about it and he described the phenomenon as an "undesirably normal condition" that others have reported. Then some rasonable explanation about getting the car to run well at all temperature, fuel mixture, etc corners and that they have to recert the car to federal emissions any time they tweak anything, etc.

Worth checking the dealer though to see if they've got more recent ECU firmware to upload into your engine controller that might be better though.

Best Regards,

-- Todd H.

2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA
Reply to
Todd H.

Try driving a little more aggressively for a few days. Mine does the same thing, but I think its the ECU learning itself into a "this guy doesnt step on the accelerator hard, let's conserve gas now!" mode. I mostly use my car to get to work and back and spend my time trying to keep gas milage as low as possible for entertainment.

The sound on mine goes away when I drive around like an idiot (like everybody else on the road it seems) for a few days.

The sound: felt through brake petal at st>

Reply to
Sparky Polastri

Todd,

Is it all that common for owners to go to the shop and see if there are any ECU firmware updates for their car? Does Subaru have firmware revisions coming out a lot? If so, is this something they can program into the unit by just plugging into it, or do they have to actually swap out hardware like a chip, etc.?

I'm curious cause I've got a 98 Legacy Outback that I might want to go talk w/ them about.

Todd H. wrote:

developed a low

happens with

Reply to
darealclemshady

At least on my 01, they blow the new code into the ECU via a simple hookup. Mine's had 2 code updates done in the normal course of service. I think it's among the first things they check when there are driveability concerns that don't have any check engine light (CEL) codes associated with em.

Doesn't cost anything to ask. They should be able to read what revision o fhte ECU code you have in about 2 seconds with their diagnostic scanner, and know if anything later is available.

Best Regards,

-- Todd H.

2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA
Reply to
Todd H.

They probably program it with the diagnostic port. I know cobb tuning has a access port thing you can upload maps for mods to the ecu on a wrx via the diagnostic port, it will pull codes too.

Reply to
Michael

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