Rough Running and Idle in my 2006 Turbo Legacy

[Banksy02]

So i have been experiencing rough running and shaking in the car when stopped at lights and my foot is on the break. Almost felt like it had dropped to 3 cylinders. it did this for about a week before throwing one CEL.

 

Took it to my mechanic where he did the spark plugs, and 2 coils that needed doing. as apparently it was misfiring on that cylinder.

Got it back off the mechanic ran fine that evening, drove it in the morning and the same issue again. 

The mechanic has now changed all 4 coils, ran a smoke test for vacuum leaks - found nothing. Cleaned the throttle body, and scanned the car whilst driving and apparently cannot find any faults with it. He notes it seems to really play up when cold, then as soon as it heats up the car is good as gold.

 

Im at my wits end here as he says he doesn't know what else to check. He has tested the VVT and they occasionally are showing funny readings. He recommends if he cant fix it my this Monday to take it to a subaru specialist here in CHCH.

 

Any advice from anyone that has had similar issues in a 06 Spec B Wagon.

[boon]

AVCS oil filter blocked or fallen into the solenoid?

Only doing it when cold, hmm. On an older car I'd have said maybe IACV but I don't think these cars have them, if they're e-throttle.

[Banksy02]

Im getting him to check the AVCS today, so fingers crossed thats it.

[Andy_Mac]

Has he had spark plugs and coils out and test fired them to prove they are all working fine? I had a spare coil that would work for a few mins then fail for a few then come back again. Is he doing any logging to see what parameters spike/fall over when it does start to run rough? AVCS is a good thought as it'll behave weirder when the oil is cold if partially blocked then come right once thinned out

 

If he has no luck just take it to SAS or Crowesport 

[Banksy02]

so we have done all new coils and plugs and he said he tested the coils and they were working fine. 

 

He is going to do some logging when its cold to see if he can pick up anything, so will see how that goes. The only thing he can really see so far is something to do with VVT voltages??? seem off when its cold. if i have that correct, that started going a bit over my technical knowledge there.

 

Unfortunately it only ever threw one CEL which has since not come back.

 

Would you recommend those two garages over m45?

 

thanks for the help Andy!!

[Andy_Mac]

Never heard of m45 but crowes and sas are pretty decent. Anyone somewhat specialising in Subaru’s should make it easier than a generic mechanic not familiar with any quirks these have. 

 

What was the cel you had? Or was that just a misfire on that one cylinder?

 

What's the engine km and oil thickness used? It's not uncommon for the avcs curves to be a bit laggy if cold or the strainer is partially blocked. 

[Banksy02]

Engine Ks are around 120000, the CEl was just the one misfire and that has now gone. Oil was sythentic 5w-30 i believe i put in.

[Loren]

Fuel enrichment when cold causing issues maybe? Or maybe the temp sensor is bad, so fuel enrichment is not happening.

 

There will be a bunch of things different in the tune when it's cold.

 

Edited September 8, 2023 by Loren

[Banksy02]

So I have a update. Took it to Crowes. They found it still misfiring on 3. Took the coil out and swap cylinders and the fault followed. Tested the brand new coils. 2 were running at 7v. Tested another subies coils in mine - all then ran at 12. So ordered me yet more coils these ones ran at 12v and now I haven't had a issue since. The head mechanic there said it was a weird issue which he hadn't run into before. I'm just glad all it needed was more new coils....

[Andy_Mac]

38 minutes ago, Banksy02 said:

So I have a update. Took it to Crowes. They found it still misfiring on 3. Took the coil out and swap cylinders and the fault followed. Tested the brand new coils. 2 were running at 7v. Tested another subies coils in mine - all then ran at 12. So ordered me yet more coils these ones ran at 12v and now I haven't had a issue since. The head mechanic there said it was a weird issue which he hadn't run into before. I'm just glad all it needed was more new coils....

 

Weird, were they genuine ones or aftermarket? Genuine ones are usually reliable as hell