Cylinder 2 Cold Misfire

I've been trying to figure this out for months now to no success. I know there are other misfire threads out there but mine is somewhat intermittent and I'm determined to track it down.

 

I have a cylinder 2 misfire and slightly rough idle that comes after the car sits overnight when cold. It goes away completely after a few minutes and if I attempt to drive anywhere if I clutch in or come to a stop without being adequately warmed up it will stall and seems to flood itself. (Probably due to the high idle when warming up)

 

What I've tried:

 

• Cleaned MAF
  
• New plugs
  
• New coils
  
• Replaced Fuel Injector Seal
  
• Replaced Fuel Injector
  
• Raising Idle to avoid stalling. (Didn't help)
  
• Boost leak test
  

 

What should I do next? Everything runs great and idles fine when warm. Even after sitting several hours.

 

Appreciate any advice I can get on what to do next.

Get a diode set to test the injector pulse from the ecm. Are you running lean or rich on either side?

 

Have you checked compression or leakdown?

It seems to be running normally and I plan on doing a compression test soon. I still think its more likely something like this: http://legacygt.com/forums/showthread.php/diy-rough-idle-cold-start-cold-temps-lgt-07-09-155325.html even though I believe I already have the revised o-rings. Some type of vacuum leak maybe...

Well what are you waiting for pull the intake off and check, or get some ether and spray around the intake base while the engine is running.

It can also be a lean running condition, check for manifold crack and gasket issue between manifold and head.

Replaced intake manifold o-ring, noticed old one was a little burnt and slightly crushed.

http://i.imgur.com/Be3pvqQ.png

 

It was good for quite a while until today. Started up the car this morning to warm up (about 10°F outside) and it actually stalled warming up with a P050A on the AP. Idle always jumps up and down on a cold start a little bit. I got the P0302 again later on and it seems what triggered it was some steep hills in first gear.

 

Onto the next thing...

Look at the PCV valve so it's not acting up - that can lead to some strange problems.

 

And as a last resort if you can't find anything else that's wrong check the valve clearance. That's one thing that may cause the problem too - and it's hard to spot.

 

If the valve clearance is tight but still sealing then it won't show up on a compression test.

Car still stalling on a cold start sometimes. Compression test around 115-120 cold on all 4.

 

I did some roughness monitoring and noticed it only happens when returning to idle. If the engine is revved, the roughness starts as soon as it falls back to idle. The more the engine is warmed up the less roughness counts I'll get. Eventually little to no roughness will show and it will return to idle fine.

 

Here is after a short drive, the 90 count is from the cold start.

http://i.imgur.com/fnynBQW.jpg

 

If I put load on the engine on a cold start it will stall and be a difficult start.

 

I am thinking valve clearance issue, would that show these symptoms? How hard would it be to check/adjust clearance without pulling the engine?

Just check for other leaks first and also check the MAP sensor and TPS sensor, if you can read/log those then it may add some more info to the equation.

 

But the roughness on 2 is disturbing.

 

Another thing - swap the cylinder 2 injector with another cylinder too just to make sure it's not a mismatch in flow from the injector.

I've swapped injectors before with no difference. It's particularly worse on colder days.

 

After I bought the car I called the dealership it was serviced at to find out if I needed to do the timing belt. They told me the engine was replaced about 25k miles ago now and there was this intermittent misfire issue.

 

Other than the p050a I mentioned, it keeps pointing to the same old p0302 and nothing else. I'm wondering if the dealership had messed up a valve adjustment or something.

Or something physically wrong with the piston, maybe too small for the bore...grasping here, lol. You should pull your valve cover and check the clearance on the valve, if that is what you suspect.

Starts to look like it's time to check the valve clearance. I'm still worried that there's a crack or bad seal in a concealed place. Like where the manifold meets the head, even though you have replaced the donut gasket. An issue with the TGV system is also an idea. There shall be a seal on the TGV axle behind the sensor.

Smoke tested and found throttle body coupler clamp came loose but no other leaks. I guess I'll get a set of feeler gauges and pull the valve cover. Hopefully it's not too much of a PITA with the engine in.

^^^Um it is. Not impossible, but a whole lot easier with the engine out. Good luck. Hope you find the culprit.

Pulled driver's side valve cover and checked clearances. Sure enough they're all pretty tight and an exhaust valve for cylinder 2 seems to have no clearance at all.

 

Think I might trim down that bucket if I can for now and when I get a chance to pull the motor I'll get them all properly in spec.

 

Could I get away with pulling the cam to get the bucket out without messing up the timing? I'm in a little bit of a rush as I'll have to move the car relatively soon.

Hahahaha, not a chance. You are just asking for trouble trying to do that. Pulling the engine is realistically a 2 hour job for an experienced diyer or a 4 hour job if you are learning as you go. Any more than that and you are being abundantly cautious. My PR is start to engine out in 1 hour on my 03 forester.

I ended up putting everything back together. Gonna shop around for quotes for a complete valve adjustment and go from there. Don't have time and insurance to do it myself.

As it is an exhaust valve I'd pull off the head too and make sure that the valve hasn't overheated at some point in history.

No matter how you look at it, the engine needs to come out.

I don't know what the hell happened but for the past 2 days absolutely 0 roughness counts or misfires even on the cold starts. Pretty sure it missed on the first start after putting the valve cover back on but after a 100 mile trip that same day it just went away? Fingers crossed...

Just hope it's not the valve guide that's coming loose in the head.