DIY: Rough idle in cold start/cold temps LGT 07-09

[StkmltS]

Did the compression test, here are the results (cold engine btw):

 

Cylinder #1 dry 130, wet 110

Cylinder #2 dry 110, wet 113

Cylinder #3 dry 130, wet 126

Cylinder #4 dry 107, wet 103

 

I'm wondering why the driver's side is lower than the passenger's one.

 

Also checked for vacuum leaks with carb cleaner, found none. Test drove the car, no CEL and it drove great. This morning I let the cold car idle in the garage and monitored the misfires with Rom Raider. For a minute there were none at all and I was getting hopeful, but then the count on #4 just shot up and the CEL came on eventually. See attached image for graph on the misfire count over time and engine speed.

 

Also, there are some misfires on all of the other cylinders from time to time, but no more than one or two before the counter resets.

 

So, I'm wondering the following:

 

- Why did the misfires show up only after a minute or so and not right away? What changed within that one minute that could trigger them?

- If everything were normal in the other cylinders, the misfire count there should be zero, right?

- Can one or two misfires be dismissed?

- Can it still be the fuel injectors if I'm seeing misfires in pretty much all cylinders? Maybe we need to look at the bigger picture?

 

Thanks for the advice, StkmltS, I will check your post. For now my suspicions lie with fuel delivery since I already excluded ignition and combustion air.

 

Looks like it's time to start your own misfire thread.

It keeps things on-topic and focused on your particular car/symptoms.

 

My misfire count never got that high, but otherwise my graphs pretty much look the same as that one.

 

People on here tend to jump on the cracked piston bandwagon a little too quickly (because it happens ALOT), so just to fight the crowd I'm not going to say I think you have a cracked piston(s).

 

Based on your numbers I'd focus on cylinder #4 to diagnose the problem. Whatever is going on in there is probably what's happening to the other cylinders. Buy a [ame=http://smile.amazon.com/gp/product/B00EQNCMTY?keywords=borescope&qid=1454093667&ref_=sr_1_3&s=instant-video&sr=8-3]$20 usb borescope on Amazon[/ame] and poke around inside the cylinder to see if there's anything obvious.

Edited January 29, 2016 by StkmltS

[kashmerekitty]

Found the issue for rough idle. It will happen more in the cold for this issue.

 

First, put a fog machine on to detect the leak spot. Found it coming from the passenger side of the intake manifold. We determined it was actually coming from the TGV. To get to that or anything really the IM had to come off. Discovered seals that when out under boost pressure pop out and cause the small leak and rough idle.

 

We used aluminum tube to make a spacer to fill in the empty space between the seals and back plate. Put it all back together after a soda blast to clean carbon on the top and remove old IM gasket. I also replaced the TGV gaskets (orange), fuel injector seals, and plugs at this time as it was easier to access with the IM off.

 

Put her all back together and after losing some coolant as had to remove the coolant rez (messy) and fired it up!! No more rough idle until a vacuum hose from the intercooler to the intake popped off a month later (probable from being loosened up after being removed twice to replace the turbo due to the banjo bolt issue and then this issue). Put two small nose clamps on both ends of that hose and no more issues!! Feel like I have a little more power at a lower speeds now too!!

 

Hope this helps someone else it was quite a job but without labor only cost me the price of TGV gaskets, manifold gasket, and if you want while under there plugs and injector seals.

 

60k on car at this time 2008 legacy 2.5 GT.

 

pic 1 shows the black seal that pops out. Unless gap is filled would have come out again after reinstall and boost pressure applied.

 

http://uploads.tapatalk-cdn.com/20160319/5801ea64c4521db5644a4c41691f6651.jpg

 

Pic 2 intake manifold on he car while we were disconnecting everything.

 

http://uploads.tapatalk-cdn.com/20160319/af62c5357cb95def081a1d6a611ad403.jpg

 

Pic 3 IM off the car tape is mostly showing areas that we disconnected.

 

http://uploads.tapatalk-cdn.com/20160319/6f1632165ed150bcf6f306cff2bbc2c1.jpg

 

Pic 4 IM Off looking at bottom with TGV on this is the part we soda blasted. Engine side manifold gasket had to be painstakingly removed with potent gasket remover and Popsicle sticks to avoid scratching.

 

http://uploads.tapatalk-cdn.com/20160319/e860d43e26b9ade175a523fd253fde3e.jpg

 

Thanks. Loving my second Subie again!! Hope this helps someone.

 

 

Sent from my iPhone using Tapatalk

[kashmerekitty]

Sorry pic 1 is intake on the car and pic 2 is the seal that pops out causing vacuum leak and system too lean CEL.

 

 

Sent from my iPhone using Tapatalk

[kashmerekitty]

Great write up but those aren't the only issue with rough idle. The TGV valve pushes it's seal out between the rod and back plate that controls the butterfly valves. We fixed that with a plat of aluminum tube to keep them in place. Not a hint of idle issues now!!

 

Replaced those orange gaskets/rings too while in there. Old ones are hard and can leak too.

 

 

http://uploads.tapatalk-cdn.com/20160319/3a4eeb176efb990105a38fd73ce5d3d4.jpg

 

 

Sent from my iPhone using Tapatalk

[kashmerekitty]

The black seal should be pushed back in wish I had taken a pic of them how they should look before and after the fix but neglected too.

 

 

Sent from my iPhone using Tapatalk

[dortiz19]

Thanks for the write up. I couldn't find a good write up on how to replace turbo inlet/intake, so this definitely helped, even though the OP didn't remove manifold, it gave me some good starting points. It took me 10+ hours to remove and replace turbo inlet. What a pain that bracket from hell is, and I ripped out the wire to the weather connection for the knock sensor. I broke a couple vacuum lines, that of course are different sizes on the ends, so have to be ordered from the dealer, so those repairs took a couple hours. I could easily do it in 2 hours now that I know every bolt, vacuum line, and what connectors have to separate.

[Ironworker613]

Tip: Cut a slot in the manifold between the bolt holes on the drivers side.

[StkmltS]

Tip: Cut a slot in the manifold between the bolt holes on the drivers side.

 

What's your thinking behind that?

...To allow the manifold runners to stay better attached to the head without being tied to each other?

[Ironworker613]

So you can remove the manifold without the fuel lines.

[Matteo80]

Hi guys, I have same problem with my 07 LGT , after warmed up 3 minutes in the parking spot , the blue light goes off and I backed up on my Parkin spot ,by the time I reach the gate , car start to be rough for about 3-5 seconds then ,it goes away and the car seems to be ok.i don't have engine light on and I was wondering if you guys had it on when this issue showed up.my meccanic said after data log car is lean at idle, I am try a used Maf sensor now to see if something change. Thanks Matteo

[kashmerekitty]

Hi guys, I have same problem with my 07 LGT , after warmed up 3 minutes in the parking spot , the blue light goes off and I backed up on my Parkin spot ,by the time I reach the gate , car start to be rough for about 3-5 seconds then ,it goes away and the car seems to be ok.i don't have engine light on and I was wondering if you guys had it on when this issue showed up.my meccanic said after data log car is lean at idle, I am try a used Maf sensor now to see if something change. Thanks Matteo

 

I had the same code, and tried new cleaning MAF, new MAF, new car battery (I know but it was recommended somewhere), and still had no fix. It wasn't until I got on to the vacuum leak bus that it all came together. I'm pretty sure this is a design flaw in the TGVs. It's more than a weekend repair too. Took 15+ hours total to diagnose, and remove all parts to get to the offending area. I took advantage and replaced the injector seals, and spark plugs while I had the TGV, intake and everything else off the car.

 

It's such a small leak that I didn't notice the issue until it was 35 degrees or below. The car never fully stalled, but ran really rough in the early mornings, or until the car was very warm!

 

Good luck I hope you get it fixed.

[Matteo80]

Thank you. Yes I have same symptoms as you. I hope too fix it soon.take care

[PraguePrado]

I joined this forum just to thank you all for discussing this issue... and to say that the leaking intake manifold gasket is definitely not limited to 2008 or earlier (or whatever the latest year mentioned in this thread so far). I'm really surprised that I haven't found many, many more threads about this issue elsewhere on the net, given the number of vehicles that must be affected.

 

I live in Tokyo and purchased a 2011 Subaru Legacy 2.5i EyeSight Sport Selection in 2020 with only 45k km on it (not uncommon here in Japan). The first winter I owned it, I experienced the exact same problem (runs fine until the blue light goes out, then hesitates until fully warmed up). I wasn't about to mess around with dental picks, etc, so I paid a mechanic about $200 to change them for me... a good deal for me, given that he said it ended up taking him about 5 hours. The original gaskets were black rubber, thinner, and much harder than the replacement gaskets (14035AA492).

 

The difference is night and day. No more hesitation, and I'm pretty sure that the car is running much more smoothly at any speed or temperature.

 

I just purchased the exact same model from auction and am shipping it to the UK to use there; I haven't even driven the thing but I've already bought the gaskets and will get them changed out as soon as the car arrives.

 

Thanks again.