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New to me '06 OB 2.5i. Engine hesitation and slight shaking under load


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Hi, all. I just recently picked up an '06 Outback 2.5 (non-XT) and have been working on getting it back on the road. It hasn't sat long at all, couple months at most before I bought it. Previous owner parked it after it wouldn't pass CA smog due to a check engine light, turns out it was a bad oil pressure switch on the passenger side VVT solenoid. Got that replaced, no CEL now, however the engine isn't running quite right.

At idle, if I give it gas, it hesitates and shakes some like it's about to stall for maybe a half second before it picks up. When driving, I'll feel the engine shaking/vibrating when accelerating even modestly just about through the entire RPM range. If I let off, the shaking stops immediately, same if I pop it in neutral. It seems to be idling fine around 750-800rpm. There's a bit of blue smoke on start up after it's been sitting overnight, not a lot but a small puff. 

So far, I've replaced the air filter, cleaned the back side of the throttle body (facing the firewall), cleaned the MAF sensor and put a bottle of fuel system cleaner in the tank. I went through and cleaned my battery connections, ground points that I could find, and MAF sensor. No oil on the plug leads or plug bodies. Plugs themselves looked good, not black or anything unusual. Nothing seemed to make any impact on the hesitation I'm experiencing. I took this short 1 minute video sitting still to show what the RPM does with different throttle input. If you roll on gentle, it picks up fine but quickly pressing the gas makes it shudder and bog some before it catches up. You can definitely hear the shudder and see it by the shadow on the middle of the wheel.

 

 

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really good start on the diagnosis.

others with more experience will chime, but, wondering if you noticed if the plugs were NGK?

even if the CEL is off now, you might scan for pending codes. If you own a smartphone, you can use an app like Piston or Torque light, with an adapter like ELM327 BT or similar (check Amazon, not expensive) and read codes, plus more.

 

If it behaves better IMMEDIATELY (less than 2-3 drive cycles) after a battery disconnect reset, that could point to a sensor signal being bad. If not, could be something more physical like a dropped valve guide or bad plug wire, etc.

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Plugs are also NGK. I do have a BT adapter and Torque Pro already and have used it to see what's going on. The thing that stood out to me most was it seemed to me like it's running pretty lean. AF ratio showed around 14-14.5 at idle, not sure what's normal and not. I'll drive around and screen record Torque to share that, hopefully that'll be helpful.

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Did more poking around looking for anything obvious I may have missed, but nothing jumped out at me. I went for a drive around the block a few times with my phone screen recording Torque Pro as I went along to capture the sensors I have on display. I wish I had added a throttle position display, but forgot. It was about an 8 minute drive, I've sped the video up 2x. To me, the only concerning thing I was seeing was the AFR spiking way up to 20+ when I let off the gas. Could be normal, just never monitored it on any other car before. Engine vibration is happening between roughly 2000 to 3000 RPM. Hopefully this will help out, I'm stumped at this point.

 

 

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ideally, you want fuel trims to be 0 or single digits. I THINK in the low 30s gets to the max the ecu can correct. So, it seems you could have a 'moderate' vacuum leak. Vacuum is high during engine braking so, that could be a clue?

Timing seems a little retarded, but I'm not sure. Others will likely have good ideas.

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This issue points to cam belt timing being misaligned to me. 

It’s best to check all three marks lining up as you can have botch cams timed correctly together but the crank mark out a tooth or two. 

Sort this out and the stumbling will go away. If cam timing is out it could possibly affect the manifold vacuum on engine braking too. 

Cheers 

Bennie

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11 hours ago, Vargrklaw said:

Pull radiator and fans to make more room?

That certainly helps! 

If you don’t want to drop the coolant (I avoid it if possible!), you can remove the fans an put a piece of cardboard or a solid board across the radiator to help protect it from damage. 

Cheers 

Bennie

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So, I pulled the fans and driver's side timing cover off and this is what I've found. Didn't pull the whole cover and pulleys off since I don't have a socket and bar big enough for the balancer pulley yet. With the cam mark aligned, the notches on the balancer are around 20-30 degrees retarded? Is that normal?20220211-141957.jpg20220211-142111.jpg

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I’ve never compared the timing marks to the cam timing before. 

On the LHS cam wheel is an arrow on one of the arms. When pointing in certain directions it tells you which piston is at TDC for the ignition spark phase of the cycle. 

You could try using that to see if anything is out, but it’s still a shot in the dark as to whether things have moved or not. You really need to view the crank timing mark alignment. 

The crank pulley is a 22mm socket ;) 

Cheers 

Bennie

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I'll have to pick up a socket soon then and take the rest of it apart to get the entire cam cover off since it's one piece aside from the small section on the driver side. Can't do it now, have to wait a while for work to slow back down :/

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1/2" drive six point socket.  22 mm or I think 7/8" also fits.  You can put the breaker bar on the drivers side frame rail just inftont of the battery and hit the starter.  A VERY short crank will break the bolt loose.  It's at 225 ftlbs I believe.

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13 hours ago, lmdew said:

1/2" drive six point socket.  22 mm or I think 7/8" also fits.  You can put the breaker bar on the drivers side frame rail just inftont of the battery and hit the starter.  A VERY short crank will break the bolt loose.  It's at 225 ftlbs I believe.

 

 

don't let the engine start - pull the plugwires all off beforehand or something.

Edited by 1 Lucky Texan
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