99 Legacy Outback shaking in drive

I just got my car back on the road (temporarily, still have a cam seal leak) and I noticed that when the car is sitting still in drive like at a stop light, it shakes. Idle is right around 750 rpms. The car has 220k miles on it, recently put all new gaskets, seals and spark plugs in it. No idea on how old the ignition coil is or the engine and transmission mounts.

 

Would swapping either the coil or mounts help? The car drives fine above idle with no shaking so I'm not sure if either would help.

It could be a sticking valve, with high miles like that, I've seen it and had it happen before.

It could be a sticking valve, with high miles like that, I've seen it and had it happen before.

When I pulled the heads off I cleaned everything up quite a bit. I'd be surprised if any are sticking.

Other ideas for big things are low compression, cam misaligned.

 

Easier ideas are mess about with the plug wires.

Other ideas for big things are low compression, cam misaligned.

 

Easier ideas are mess about with the plug wires.

No cam misalignment. Low compression is a possibility but it seems fine under normal driving conditions.

 

Plug wires... have you seen any jump spark at idle but not while driving?

 

My only other thought was possibly the front o2 sensor. I figured that'd through a code though at this point.

 

Would slightly low ATF or old ATF cause shaking?

I don't think ATF would do it.

I agree that the O2 should throw a code if it was off enough to affect idle.

I have seen some slightly rough idle at low RPM over the years before the cam jump. I always felt like it was a poorly timed or weak spark as it's not as rough as a solid miss, but it isn't quite rock steady either. Plus the megasquirt gang says they have terrible trouble holding sync on 2nd gen Subarus at low RPM because there just aren't enough teeth on the crank sensor wheel.

 

When my cam was jumped it was missing spark and injector impulses at idle, and then again above 3450 RPM. Just off idle, like maybe 900 was solid. More than about 20% pedal would make it double fuel some cylinders. That was the computer losing track of where in the rotation I was. I could see a weak or sloppy crank or cam sensor impulse doing something very similar to a lesser degree. And mine didn't throw codes for the sync loss.

 

If you have a multimeter you can do a really rough test of the crank and cam sensor by probing the two wires and moving a magnet past the sensor head. If you get a blip it is sensing, but if you wanted really good data then you'll need an oscilloscope. Probing with the oscope at the computer would show if the signal was funny shaped, or if there was noise in that wire from a failed shield ground.

I don't think ATF would do it.

I agree that the O2 should throw a code if it was off enough to affect idle.

I have seen some slightly rough idle at low RPM over the years before the cam jump. I always felt like it was a poorly timed or weak spark as it's not as rough as a solid miss, but it isn't quite rock steady either. Plus the megasquirt gang says they have terrible trouble holding sync on 2nd gen Subarus at low RPM because there just aren't enough teeth on the crank sensor wheel.

 

When my cam was jumped it was missing spark and injector impulses at idle, and then again above 3450 RPM. Just off idle, like maybe 900 was solid. More than about 20% pedal would make it double fuel some cylinders. That was the computer losing track of where in the rotation I was. I could see a weak or sloppy crank or cam sensor impulse doing something very similar to a lesser degree. And mine didn't throw codes for the sync loss.

 

If you have a multimeter you can do a really rough test of the crank and cam sensor by probing the two wires and moving a magnet past the sensor head. If you get a blip it is sensing, but if you wanted really good data then you'll need an oscilloscope. Probing with the oscope at the computer would show if the signal was funny shaped, or if there was noise in that wire from a failed shield ground.

 

THAT IS A DAMN GOOD IDEA!

 

Once the cam seal is changed I'll do just that!

Motor mounts?

Why is everyone beating around the bush?!? My first thought is all 4 mounts are probably worn out: 2 engine, torque strut mount, and tranny mount. It's a 20 year old car with 220k on it. I have a 98 with 213k and shakes like a mofo at idle. Its the mounts.

Why is everyone beating around the bush?!? My first thought is all 4 mounts are probably worn out: 2 engine, torque strut mount, and tranny mount. It's a 20 year old car with 220k on it. I have a 98 with 213k and shakes like a mofo at idle. Its the mounts.

Yet it has no issues while driving? Most bad mounts I've been able to feel that something was wrong while driving... this thing drives great though.

 

 

I mean it's possible though, I'm just skeptical.

my 96 ob shakes like mjf at idle and rolls nicely while driving as well, and those mounts are about 100k past any useful cushioning power. definitely worth checking them out.

My 98 outback shakes while at idle as well. Well, more of an annoying rattle to be honest. I was figuring motor mounts as well though I haven't checked them out yet. I'm sure they are shot. None of the rest of the suspension had been touched in 21 years so I find it unlikely the motor mounts have been done. I would definitely start there. doesn't hurt to inspect them and at minimum rule them out.

Well shit they are only like $13 a piece on rockauto... I'm just gonna do all 3 including the trans mount.

Well shit they are only like $13 a piece on rockauto... I'm just gonna do all 3 including the trans mount.

 

Jeez, they are that cheap? Man I would have ordered them months ago if I knew that was all they cost lol.

I did all mine when I swapped my trans. I didn't notice the price of them compared to the used trans, struts and springs, steering rack, bushings and balls, brakes, and hoses and belts.

Jeez, they are that cheap? Man I would have ordered them months ago if I knew that was all they cost lol.

 

Just bought the two engine mounts and it equaled 34.53 with shipping for anchor brand mounts. I gotta look at my trans to find out if it is 3 of 4 bolts....

 

That I'll buy later after I see if these make a difference.

FYI everyone, engine mounts fixed 90% of the shake... the trans mount must be shit too... oh well. I'll swap it eventually.

90% fixed is good. You should have plenty of breathing room now.