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Discussion Starter · #1 ·
Hello guys, so I've been having this recurring problem where my B9 (116,00 miles) will shake when I start it up from cold. The shaking will occur for about 15-20 seconds, then will run perfectly fine afterwards. The shake feels as if a cylinder is misfiring or not firing. On the rare occasion that the shaking lasts for more than 30 seconds, my CEL will flash and a cylinder 3 misfire will pop up. There are times when it starts up perfectly fine with no shaking however. Starting the engine warm will not cause shaking.

I've already replaced the coil pack and fuel injector for cylinder 3, but if when the CEL comes on it still indicates cylinder 3 misfire. The car does not show any of the signs of a failed head gasket that I've researched such as bubbles in coolant reservoir, coolant mixing with oil, overheating, coolant loss, etc. so I'm ruling that out.

I'm hoping that the problem has to due with the spark plugs. The plugs have about 9,000 miles since I've replaced them, but they are Autolite plugs that are compatible (bought at O'Reillys) and not the NGKs.

I'm hoping you guys can chime in and help me solve this once and for all, since this is the only problem left to fix after spending $2,000 to get my timing chain tensioners, guides, and all related components and seals replaced. Thank you.
 

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Subaru's are know for being picky about spark plugs. You should put what the manual calls for exactly. Then report back.

Did it just start happening after plugs?

The other possible issue would be timing when the chain was replaced. Hopefully its not that. If it is still misfiring after replacing the plugs the next step will be logging and looking at the advance the engine management is going to the timing to see if there is an issue there.
 

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Discussion Starter · #3 ·
Thanks for the reply tdelker. I will replace the plugs with the NGKs in the manual, hopefully that solves the issue. I don't remember if it started after replacing the plugs to be honest, but if I had to guess it started a little while after. The shop where I got the tensioners and whatnot replaced (the chains were fine) is very reputable with high reviews and they have always provided me with great service, so I don't think the problem is with timing, as then it would misfire all the time and performance would be sluggish. I forgot to note that this was happening even before the tensioner repair.
 

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It's possible although I'm not sure that I've seen it, for the VVT to compensate for 1 cam being off by 1 tooth (about 10 degrees).

Plugs are most likely.

Vacuum could be another possibility. When they did the tensioner they likely pulled every hose off. I believe the fuel system utilizes the vacuum which could be an issue at startup if there is a bad leak.
 

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Gotta go with the crowd on this one. Start by swapping out the plugs for some laser iridiums (NGK# ILFR6B)
 

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Discussion Starter · #6 · (Edited)
Update: replaced all six plugs with NGK ILFR6Bs today (cylinder 5 & 6 are a pain in the ass due to limited space), made sure to torque them to proper specs this time (15.2 ft/lbs) as the last time were just tightened until they felt tight. All old plugs, except for cylinder 3, barely required any force to loosen. I'll see in the upcoming days if the problem is hopefully fixed.
 

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3rd cylinder?
swapped coil for another cylinder - error at same, 3rd cylinder, or that another cylinder?
 

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@Rafal please, use full sentences.
issues with 3rd cylinder can be many - bad plugs, valves not working properly.

if I understood you correctly:
1) I would remove plugs and look at them - is 3rd cylinder different, are all other ok.
2) get some camera and look into cylinder - may be there are issues with valve/s.
 

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Sorry, so Service swapped coils (1st for 3rd) and 303 still appears only when shaking a car while start (it goes about 10 secs and then its ok). When you press a gas pedal during those 10secs 303 error appears, if you wait - all works fine. Some user on other forum said that its cooling fluid stays at the cylinder (so begining of head gasket issue) and an engine must warm it off.
For now Service did:
1) changed all sparking plugs for brand new NGKs (dedicated)
2) make ECU repair - some transmition-data sending failure and the IT guy has to reprogram it
3) valves are perfectly setted, Service said its 30-70 or something like that (no mechanical knowledge)
And the shaking still appears but less often and its shorter.
Did about 2000 miles that way and at highway runs like a new. Just the issue is after night, when starting a car going to work.
In fact I add a zip coolant, but it was like few drops.
 

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1) did they measure gap before installing spark plugs? when helping neighbourgh with his nissan - couple of stores had spark plugs with DIFFERENT gaps :D (personally - I would try denso plugs)
2) if there is issue with ECU - there needs to be some soldering done. If you can't find information about it - let me know. I might be able to find information about it in my files somewhere.
3) did they do video observation of valves? did they do leak test? did they do compression test?
 

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Sorry, so Service swapped coils (1st for 3rd) and 303 still appears only when shaking a car while start (it goes about 10 secs and then its ok). When you press a gas pedal during those 10secs 303 error appears, if you wait - all works fine. Some user on other forum said that its cooling fluid stays at the cylinder (so begining of head gasket issue) and an engine must warm it off.
For now Service did:
1) changed all sparking plugs for brand new NGKs (dedicated)
2) make ECU repair - some transmition-data sending failure and the IT guy has to reprogram it
3) valves are perfectly setted, Service said its 30-70 or something like that (no mechanical knowledge)
And the shaking still appears but less often and its shorter.
Did about 2000 miles that way and at highway runs like a new. Just the issue is after night, when starting a car going to work.
In fact I add a zip coolant, but it was like few drops.
Please update your signature or profile listing your vehicle year. I have been doing this for alot of the newbies here but I am burnt out with it.
 
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