Vibration only at idle and at 2000rpm approx

Hi everyone,

 

I am the proud new owner of a 1997 Outback.

 

I have spent most of the day reading everything that I think is relevant on this forum to my problems with the car.

 

Before I bought the car I had a mechanic check for fault codes, it through up codes for both O2 sensors, so they will need replacing asap. I thought about buying cheap O2 sensors but after reading here that Subaru's are picky about which O2 sensors work well I will go for the more expensive recommended ones. As I have never driven an Outback before I have no idea if or how much this sensor problem is affecting performance. I have to say for a 2.5 engine it didn't feel very fast but it felt very smooth power wise through the gears.

 

The other most frustrating thing is a vibration that feels like is coming from the engine, it happens at idle while the car is in Park, neutral, or Drive ( or any other gear while stationery) As soon as a very small amount of extra revs are given the vibration goes away, but comes back at approx 2000- 2200 rpm, this happens at this rpm through all gears but only while on the accelerator like going up hills etc.

 

My first thought was an engine mount, but I read here that engine mounts almost never fail on these cars, but after looking at the engine at idle it does look like the engine does rock side to side a bit more than should be expected?? Although I am not sure if anything else could cause this including the famous axle problems that I have read about? As nothing vibrates unless the car is accelerating with engine force I can't check what's happening by just bringing the revs up to 2000rpm while the car is in Park as it doesn't vibrate.

 

I'm hoping what I said makes sense, if anyone can shed some light on the potential problem to give me a starting point it will be greatly appreciated.

 

I am hoping it's not transmission problems, but as the vibrations seem to come from the engine and not the running gear maybe it could be engine mounts?

 

I don't have any service history on the car at all, the seller didn't even have an owner's handbook. It is low mileage, and I believe due to the general condition of the car that the mileage is genuine 110,000 miles

 

Thanks in advance, it's great that a forum exists for these cars!

The engine will shake side to side a pretty fair amount if you are getting misfires. Depending on how bad your O2s are you may be poorly metering fuel enough to get misfires as you describe. But are you getting a flashing CEL or misfire codes stored? You may or may not get the codes or the flashing in a misfire.

Hi Doublechaz, thanks for taking the time to respond. No CEL light. And the fault codes I presume that they are being stored, because when the car arrived to be checked over the mechanic started checking for codes after he had checked around and under the car, I don't think any code reset was done.

 

It feels like it's a shaking/resonance problem rather than a misfire as I feel no los of power or judder of power, and the engine feels extremely smooth in the way that it pulls. just a shaking as it gets to around 2000rpm, only does it under acceleration or at idle- not so noticeable at idle but it's definitely there.

 

I tried to wobble the engine with my hands while the engine is off but I couldn't get it to wobble (the engine felt much heavier than I expected haha)

I have read lots about bad axles causing vibration, but I can't see how axles could cause a vibration while stationery especially in Park or neutral, if it can, please educate me.

 

I am going to see a mechanic today, it looks like it is well overdue for an oil change, so I will ask about the vibrations at the same time.

 

Also is there anywhere I can find an online owners manual/handbook? This car really didn't come with anything in the glove compartment

Update- problem solved!

 

It turns out that a spark plug lead had popped out and the car was only running on 3 cylinders!

 

On the 130 mile drive home from picking the car up I didn't even realize that it wasn't running on all 4 cylinders, I thought that it would have been much tougher if it had been something serious like that!

 

Now obviously it's faster, smoother and no vibrations at all at any rpm under any driving.

 

I feel a bit dumb with it being such a simple but important thing!

 

The mechanic said that the cable probably wasn't pushed in properly by whoever last services or checked it. And fell out after I had picked it up, which fits well with my experience as I didn't feel any vibration on the short test drive, although I was unable to get it up to speed as I was stuck in a city in traffic the whole time so I thought that the problem must have existed before.

 

Anyway, very happy with the 0 cost repair. Oil change done, O2 sensors will be done at the end of the month when I have some spare cash for it.

 

I'm so pleased it was something so simple!

First Subaru, right? The balance in the H4 engine is so good that one cylinder out is a good deal less shaking than one cylinder out in other engine designs.

 

Glad to hear it's solved. But I'm kinda surprised it didn't light the CEL. I had one work loose once and the CEL was on before I could even sense that things were not right.

Yes, first Subaru.

 

And no CEL light at all, maybe the CEL bulb has been removed, I am guessing it should light up for a second while starting the engine or when the ignition is on, I will have to take a look.

 

The thing that is amazing to me is that for a 21 year old car the suspension transmission and general running of the vehicle feels like it's brand new. I have owned various old cars- Supra 1987 3.0 NA, Ford Probe 1995 2.0, Ford Probe 1996 2.5, Mitsubishi GTO 1998 3.0 Twin Turbo, and none have had this 'like new' feeling like this car.

No check engine light during startup or while turning key to ignition, so I'm assuming the bulb has been removed?

That might explain that. If you get in there to fix that, be careful with the various connectors going to the cluster. Some are card edge onto the cluster's circuit board and are somewhat delicate. Mainly the trouble is they are hard to work with in the limited space.

I noticed on the '98 GT (that my son has away at college) that the engome has some shake to it around 2000 RPM when the car is in neutral. The one thing I've never checked over on this car is plus and wires since they were fairly new when we bough the car- worth the look the next time he's at home.

I was having a little trouble with my wires seating deep enough at the coil. I think that may have been before I knew about using a hairpin or something to let the air out from under the boot when putting it on. Especially with dielectric grease it traps the air and pushes the darn thing back off over time.

That's interesting Doublechaz, and can explain perfectly why it popped off.

 

Stevo F, any updates?

It feels good to have a solid reason why something heppened. I hate mystery breaks because you never really know if you have fixed it for good, or just for a little while.

No updates- I'm trying to get my son to bring home so i can change the oil and then I can look at it- hoping it's something simple like plugs or wires

Update (finally). Since my son is home from college with the '98 GT I fnally had a chance to install new NGK plugs and wires to see if it took care of the engine shake around 2000 RPM. It does seem much smoother in that range. The old plugs weren't terrible and wires looked OK. I did notice the cylinder #1 plug wire came off very easily so I wonder if that was part of the issue