Ignition timing fluctuating severely and running rough

Hi, sorry this is a long story may pay to get some pop corn

I have looked over countless forums for the last 6 months trying to fix or at least get a clue as to why my 2004 BL Auto legacy GT is running with a rough idle and shaky acceleration some of the time.

I took the car into a workshop to get them to fix the issue who proceeded to check the following

Spark plugs (replaced)

coil packs all check on a tester and were good

compression was fine

injectors seemed fine

Maf sensor fine (also tried cleaning it which done nothing)

other stuff too which i cant think of at the moment but will update this evening.

Basically he was unable to find what was wrong so he took it to Subaru to plug into their computer which reported that it was fine and they couldn't even feel the shaking.

The car shakes from gently to mildly when in neutral stationary, almost never in drive with my foot on the brake but can feel it miss under acceleration and sometimes cruising speed.

The car is awesome on petrol and uses little to no oil (not perceivable between oil changes).

Does it both cold and warm and varies intensity between them both.

I have purchased a vag com cable and plugged it in and done some logging with romraider and found the only thing that really stood out was that the Ignition timing when it was shaking was varying from I think around 0 to 40 but stable when not shaking. I will post a picture of the graph tonight when i get home. The log was taken at idle with moderate missing.

So finally the question, what sensors should i log to try and narrow this down as i have a suspicion that it is just a random sensor that is throwing the timing off which is making it shake.

I thought it may be the rear 02 sensor but have no idea what values to look for as it is always between 0 and 1 volt.

Any and all help will be greatly appreciated as I truly have almost had enough with the car

Thanks

Cameron

Welcome to CS Cameron, has it still got the AVCS oil feed filters fitted? Have a read through this thread:

http://clubsub.org.nz/forum/showthread.php?22885-New-AVCS-Issue-(V7-on)-oil-feed

Do cam position sensors fail without causing a CEL? (Or as an aside, crank position sensors?)

Thanks for the quick replies

I suggested the AVCS oil feed filters to the mechanic and he checked them and apparently they had all been removed and so is the one going to the turbo.

A little bit more background, there is no CEL and no stored codes, the intake manifold has been pressure tested also and showing no leaks.

I will see if the cam position sensor (or crank position sensor) is available to be tracked on romraider to see what it is reading tonight and also try and visually check the cam position sensors for damage or oil.

Thanks again.

 boon said:

I think they can fail "within spec" so they're sending crap but it's within the margins of what the ECU expects so instead of throwing a code it just runs like ****.

Yep that's right, mine did the same. Ran like crap but wasn't throwing a code. Once i replaced it, all was good.

Whats the avcs/cam position when its running rough. Try zeroing target table and see if it still occurs.

Will do a run with romraider tonight trying to target everything to do with the cams and report back

OK Done the logging sorry there is allot of data

https://drive.google.com/file/d/0Bzc0FZGK5ELoQ3p5VHZfWktBU1E/view?usp=sharing

I hope you can access it.

The thing I noticed is the throttle duty motor is going all over the place all the time, as far as i can tell the cams are working as expected but i'm no expert. Also the rear O2 sensor doesn't seem stable can any of you make heads or tales of it?

Cheers

Cam

I cant i know nothing of the stock ecu. Cant see rpm trace vs avcs to see if same issue as mine but doesnt look it.

Sorry I didnt include the rpm but can re do if someone thinks it is essential.

Cheers

I had exactly this issue with a friends 2004 Legacy. Cambelt had jumped a tooth

Wow, ok im going to take it into Palmfields on Tuesday as it is getting worse so need to get some action and if it is the cam belt i cant fix that Thank you all for your help. will let you know how they get on.

OK took it into subaru and they found nothing wrong ...... took the guy for a drive and it stuttered so he suggested the MAF was the most likely place to start. It wasn't the maf next the a/f sensor has been suggested but that's another $600 plus install for a maybe part. I just wish this thing would throw a CEL to give me a clue. I'm going to try cleaning out the throttle body and also check the vacuum lines below the intercooler while I'm at it to make sure they are OK. Is there anyway of testing if the pcv valve is ok while i have the intercooler off or shall I just try cleaning it with throttle cleaner maybe?

Also if i use upper engine cleaner do i have to do an oil change afterwards as i have not long done one and forgot to do the damn upper engine cleaner.

Idle problems would suggest a vacuum leak in my experience. Worth checking properly if you haven't -

Could be as simple as a split line that's hard to find

Had the garage do it but haven't done it myself, will follow those instructions as soon as i get a chance gota love mighty car mods they cover everything.

did the guys at subaru do a roughness monitor test? quit common problem on these models are injectors crapping out, will give a slight miss every now and than. will drive ok but will idle funny. roughness monitor test will confirm which cylinder injector is weak.