03 Legacy GT BP5 2.0 turbo rough/lumpy idle

[jacksie66]

Hey lads. Right, so my 03 Legacy has had a bit of a rough idle for a while. It's not too bad but it's just annoying. If it's idle it feels like it's misfiring ever so slightly. If I increase the revs to about 1500 it gets much worse. But over 2000 is barely noticeable. I've had it on the diagnostic computer and there's no fault codes whatsoever. I cleaned out the MAF today which was pretty dirty but didn't seem to make much of a difference. After I cleaned the MAF I disconnected the battery for an hour to reset the ECU. It idled pretty horrible when I first started it but died down a bit after a drive. Also if I go for a drive from cold it splutters and hesitates a bit but once it heats up its fine.. Don't really know what to do next. It's always serviced on time and had 4 new plugs installed last year. Anyone have similar issues? Cheers lads.

Edited July 24, 2016 by jacksie66

[94 Leone]

plugs fouled? are all the coils plugged in and connected properly?

[jacksie66]

I only installed 4 new plugs last November. I made 100% sure everything was connected and correct because it was such a pain in the hole to change them..

[Andy_Mac]

You tried pressurising the intake to see if there's a leak/hose off?

[Rosssub]

Be worth checking out your AVCS oil feeds/solenoids too, could be a cam stuck advanced:

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

[GorGasmSpecB]

As per Rosssub. Check the AVCS solenoids for filter debris, it's super common for the filters to disintegrate and get stuck in the solenoids thus jamming the timing on that side and making it run like crap at a certain RPM. It's stupidly ironic that the one job the filter has, is to stop **** getting in the solenoid.

10 minute job.

[jacksie66]

Cheers for all the replies lads. I'm going to check the throttle body and see if it needs a clean. My old Opel Vectra back in Ireland was running rough and it was down to a very dirty throttle body. Gonna check the AVCS filters aswell. If I take the filters out do I just clean them or do they need to be replaced?

[Andy_Mac]

Pull them out and chuck them in the bin. They do more harm than good

[jacksie66]

Cheers man. Might be a bit of a struggle with a broken finger but I'll endure the pain to get rid of this annoying idle..

[jacksie66]

So I removed those 2 filters this morning. Hasn't made much of a difference if any. If there's no codes showing up on the computer as well I don't really know what to do next. I removed the intercooler to have a look at the throttle body. The butterfly valve seems nice and clean. I did notice some oily gunk around one of the seals between the intercooler and the engine.

[Andy_Mac]

Don't get too caught up on oil round the intake pieces. Without a catchcan these engines do get a small amount of oil residue Throughtout the intake.

Still reckon you should be looking for a vac leak. If you've got access to a tactrix cable you can do a learning view which will tell you if the fuel trims are messed up. Had my BOV vac hose blow off a while back, ran like death at low RPM's but as soon as you gave it some more throttle it toned back and was almost unnoticeable.

Edited July 25, 2016 by Andy_Mac

[jacksie66]

Yah that's kind of the same with mine. At high revs you wouldn't notice. If its just sitting idle it sounds like it's misfiring and the engine shudders. Its particularly bad at 1500rpm. Above 2000rpm it disappears. I've got no access to one of those cables. I'm just hoping it's nothing major. This is my very first turbo car and I've heard horror stories!

[Andy_Mac]

Just have a good search around the engine bay for any plugs/hoses that may have popped off for a starter.

[jacksie66]

Had a good look a while ago and couldn't spot anything. Even sprayed spots with washing up liquid to see of any bubbles formed. Nothing. Also when I disconnect the battery for about and hour and then reconnect it the car idles really badly. Super rough. When I went for a drive it calmed down..

[jacksie66]

I usually run 95 fuel in my car. Would 98 make a difference?

[Nith]

I had a very similar issue with my Legacy when I decided to change my Blow off / divert setup to vent to atmosphere. Car would idle badly and almost stall the engine (being an automatic, not ideal) Changed back to recirculate and it went straight back to normal. It could be a leak or your recirculate pipe could be something to look at.

[Subirex Automotive]

so you pulled out the filter, great, did you actually check if a tiny amount of that plastic has broken down and got stuck with vvt solenoid? the vvt solenoid will need to be pulled out to see if it has something stuck in it. it can be a pain to get to but its worth checking. or other option could be to get hold of someone with a decent scanner and read the live data on the intake vvt. normal specs are between 0-20 degrees. normally when the vvt gets stuck, it sit at 50 degrees.

another common problem on these models that can cause this is a vacuum leak. the bov vacuum hose in the intake manifold tends to fall off. also would be wise to get your injectors checked.

[Timmah]

If you're on Facebook, get in touch with Specialised Auto Services (SAS) https://www.facebook.com/SASworkshop/?fref=ts

Jason can hook up his laptop and take a look at what the ECU is doing.

[JDM-SpecB-BP5-Legacy]

On 25/07/2016 at 4:24 AM, jacksie66 said:

Had a good look a while ago and couldn't spot anything. Even sprayed spots with washing up liquid to see of any bubbles formed. Nothing. Also when I disconnect the battery for about and hour and then reconnect it the car idles really badly. Super rough. When I went for a drive it calmed down..

 

I have a JDM SpecB Legacy with similar idle problems as jacksie66 is experiencing.

 

I'd like to know if jacksie66 you ever were able to figure out the root cause and solve the issue?

 

I have btssm monitor on the ECU and the AVCS solenoids are equally controlling the intake for both left and right, but still not certain if the AVCS gear(s) are worn out.

 

Checking the grounding next.

 

I have replaced spart plugs and the ignition coils.

 

FYI: My car is also converted to run as CNG and the same problem is with gas as petrol, so this is not related to fuel injectors.

 

Any idea what I'd need to check next?

[Andy_Mac]

Do a learning view snapshot and see how that looks. That’s usually the best starting point as if there’s massive corrections to fuelling then you’ve probably got a leak somewhere

[JDM-SpecB-BP5-Legacy]

Thanks Andy for this tip.

 

Attached below are my LV values and they do not seem to be too much off?

 

Do I understand this correctly, that with regards to the "Fuel Correction (%)" Learn % values,

a) a positive value indicates that the ECU has figured out that more fuel is needed as compared to the "standard engine with all ok"?

 -and-

b) a negative value indicates that the ECU has figured out that less fuel is needed as per the standard situation?

 

My car is being maintained by a Subaru / Mitsubishi specialist who did confirm recently that there are no leaks.

 

I'm kind of leaning to the fact that my left cam gear is worn off as after a ECU reset, the idle is really all over the place (which was not the case before) . until it settles.

 

BRIEF HISTORY: The left intake AVCS solenoid was stuck and the idle was lumpy (piece of plastic or sealant stuck the solenoid) - once this issue happened, I had to drive the car for 350 kms. The AVCS solenoid was replaced and all came back to normal. This was about 2-3 months ago, but now during the last weeks the idle seems to resemble the situation when the left AVCS solenoid was stuck. My feeling is that the problem caused by the left intake AVCS solenoid being stuck was initially not visible, but this problem is now getting gradually worse. The self calibrating nature of the AVCS would explain this as likely the left AVCS is over advanced even though the BtSsm monitor indicates the "VVT intake" for L & R sides to to hand in hand (0 = idle, 10 = cruising and 30-40 when accelerating). My estimation is that actually the the left side AVCS gear is about to be toasted.

 

The mechanic will open (and likely replace) the left AVCS gear (and I'll request him to flush the left AVCS oil lines to ensure there's no debris).

 

FYI: The banjo bolts should not exist on this engine as it was rebuilt about 30k ago.

 

If you'd suggest me to check something before the AVCS gear replacement, I'm open to suggestions - Thanks!

 

 

[Andy_Mac]

Idle is always crap after a reset as it needs to relearn so don’t look too closely into that. 
Those learning view corrections are a bit high but not in the idle region 

 

Have you got an aftermarket intake or anything on the car? The two mid figures would indicate something not 100% right 

But since they’re still in a region where you’re not really making positive pressure in the manifold it doesn’t specifically point to a leak. 

 

This is based on how it looks in the old windows program but still helpful.