Rough Idle & Engine Shaking under load like Aircon On

[ilib11]

Hi All,

Got some issues after a dealership did a service and need your collective knowledge to understand what is going on.

 

Legacy (Liberty) GT, Auto, 2010, 100K miles . Went to the dealership for one of the typical service, got the car back with strange symptoms - engine is shaking on idle on added load like AC compressor turning on or a transmission set to reverse.

 

With AC compressor, each time when it starts when engine is idling, there is a vibration wave for a couple of seconds. It is quite significant - can be physically sensed by hands on the steering wheel, via the driver chair, hood is visibly shaking etc.

The engine looks like choked, rpm dropped for couple of seconds and then comes back to a normal idle work. No such issue on rpm higher than idle.

 

With transmission put in reverse and the vehicle is kept stationary with brakes or with very slow moving backwards, it is the engine rough idle and a high vibration. If AC starts at this moment, the vibration becomes worse.

 

Apart from this vibration, the car drives good, no problems with acceleration, no strange sounds, does not look like it has any misfiring. Real time data from ELM327 dongle & Torque and Rom rider logs look ok.

 

I tried to return the car back to the dealership but they unable to actually fix the issue. They increased idle by approx. 100 rpm, so the vibration become a bit less but the issue is still there. They mentioned an adaptation/relearn period after a battery disconnect but after a while the issue is still there. Plus I do not recall any previous battery disconnects did anything like that. Unable to get them to fix the issue.

 

I spend significant effort doing various tests and parts replacement while trying to find a root cause for the issue. The discussion is here in AU forum:

http://forum.liberty.asn.au/viewtopic.php?f=18&t=36648

 

 

I can now say what it is NOT:

 

- spark Plugs (new NGK)

- ignition coils (new OEM)

- MAF (new OEM)

- first O2sensor (new OEM)

- PSV valve (cleaned, checked)

- throttle body unit (cleaned, swapped to another one used OEM)

- air filter (new)

- battery (new)

- any rubber pipes etc I can touch without taking off the intake manifold

- electricity noise or problems (oscilloscope shows stable supply with no noise mostly at 14.2-14.4 v)

- oil cap

- no intake leaks are found by a reputable service and myself.

- petrol (use 98, the symptoms is worse on 95 though)

 

 

Other checks I completed:

 

- Fuel

51 psi with vacuum disconnected

41 psi with vacuum connected and AC off

42 psi with vacuum connected and AC on

 

39 psi-> 40 psi -> 41 psi when engine is off

 

 

- Intake vacuum

20 mm Hg with A/C off

17 mm Hg with A/C on

(measured at brake buster pipe)

 

 

- Cylinder compression with open throttle (slightly warm engine):

1 cylinder - 9 bar (130 psi)

2 cylinder - 10 bar (145 psi)

3 cylinder - 9.5 bar (138 psi)

4 cylinder - 10 bar (145 psi)

 

 

I am practically out of ideas what else could be a reason for this issue and how to fix it, at the moment the only workaround I have is to increase Iide RPM settings as + 200/300 rpm via Rom Rider, but that only reduces the symptoms to some extent, not a fix.

 

I appreciate any of your help and advise on that problem. I truly hope someone knows a solution for that.

 

Thank you and best regards,

ilib11

[tony saurus]

It’s a long shot but it’s possible a belt tensioner/ pulley may be in the process of locking up. Considering the complete technical data, I’d say it’s not likely you would have missed but it’s all that I can think of. I’m pretty positive that fuel/ electric issues would be demonstrated to a degree that you can recognize if that was the issue. The ONLY other possibility I could entertain would be bad fuel, did you fill up at a different station? Again a long shot so sorry if I’m just beating a dead horse.

 

 

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[ilib11]

Hi Tony,

First thank you for your suggestion, every bit helps!

That issue is a long problem - have been trying to fix it over 6 month now.

So multiple fuel stations have been used - the only difference is that the issue is a bit worse on 95 petrol than on 98 petrol.

 

How long would you think the belt tensioner/ pulley would last if it started locking up? I have 5 years and 62K miles (100K km) since the timing belt was changed, a would assume belt tensioner/ pulley would have changed as sell at this time.

[tony saurus]

No idea how long a belt tensioner would last if “going bad” but maybe if it’s been this long, then it is a rotating assembly of some sort. It could be relative to the torque converter too. Not sure how it is engaged at an idle but again: a physical component without sensors is all I can figure.

 

Definitely get an old school mindset if the sensors say everything is fine. Proper diagnostic process can save a lot of grief but some of these old heads have seen it all

 

 

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[ilib11]

I think I can exclude torque converter from this equation because I can replicate the problem with just extra load from AC, even if the auto transmission is set to N.

 

If I put auto transmission to R it adds load to the engine the same way as AC does or adds extra load to AC and makes problem worse if AC is already on. So I do not think the root cause is in torque converter / transmission, but if there are any extra tests I can do I am happy to do them.

[tony saurus]

I am going to agree, it’s unlikely; however, not impossible. I’m not sure the logistics of how a torque converter affects engine load at an idle / in neutral. I only know that a clutch issue can do so with a manual transmission in particular situations in my own experiences.

 

Sounds like it isn’t trans / torque converter related so I am stumped.

 

 

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[ivan.ej255]

Hi, my 2010 5EAT LGT is having this kind of vibration too. I have been chasing this 'problem' since I got the car in 2018 and now I kind of gave up already lol. The vibration is actually not bad like how a solid engine mount would vibrate, but it's still very noticeable and I kind of just accepted that this is how the Legacy 2.5GT is. Kind of annoying knowing this is a midsize car which should have better engine NVH at idle than compact cars but my old 8th-gen civic is actually smoother at idle with load or not.

 

Like you, I have changed all the possible culprits with all original Subaru parts from the dealership:

 

All 4 spark plugs (changed it 3x within 1 year/10,000km just to be sure)

All 4 ignition coils

MAF sensor replaced 2x

Throttle body cleaned 2x in 1 year

Vacuum leak/boost leak test several times

Compression and leakdown test several times

New air filter

New battery

Replaced almost all of the vacuum hoses available in the Subaru parts catalog

 

New engine and transmission mounts (1 in front, 1 on each side (left and right), 1 transmission mount)- This surprised me the most. Both old side engine mounts were trashed, but after installing new original ones there's no difference at all with regards to the vibration. In all my previous cars there's always a big reduction in engine vibration after replacing trashed engine mounts.

 

All of the parts are installed the right way, always following the factory service manual. Datalogs from romraider shows the engine is in tiptop shape. Same results when plugged in to the SSM computer at the dealership. I've also manipulated the idle speeds thru romraider and ecuflash and yes, this does not solve the 'problem' it just masks it. I have since added almost 40,000km to it since I bought and it hasn't given me any engine/transmission related problems.

 

After 3 years of chasing this with no positive results, I kind of just gave up 'actively' going after this as it's just another source of stress for me. Not to mention the amount of money spent on this lol.

 

My next step would be to install Fluidampr (replaces your crankshaft pulley). I know the USDM LGT has a different drive/serpentine belt system than the rest of the world and the Fluidampr is not compatible. If your 5th gen uses 2 separate belts for power steering/alternator and A/C like the rest of the world, the Fluidampr for EJ25 application will fit your car. If this does not solve the vibration then I'm done. I'll just fully accept it as it is lol.

[Scubaboo]

Ouch. Roughness monitor misfire count check on cyls 1-4?

[ilib11]

Hi ivan.ej255, thank you for your reply and it is a pity you spent so much effort and this issue is not resolved. Very similar story indeed. The potential difference that you got the car with it and I got this problem after the car went to a dealership service.

 

That makes me think that there is some problem(s) with engine internals i.e. in the parts we have not touched yet

 

My thoughts now are:

a) uneven fuel supply from injectors

b) blocked banjo bolts plus lower oil pressure on idle potentially causing AVCS system going nuts

c) Valves/springs

d) Catalytic converter causing too much back pressure which disrupts idle operations

 

Unfortunately I do not have a place to dismantle / disassemble the engine to check these ideas out but I am trying to find a friendly workshop that can take the challenge without leaving me without car for months and/or making me completely broke

 

Re Fluidampr - as far as I understand, it is for compensating torsional vibrations, I am not convinced it would help in my case. I have separate belts for power steering/alternator and AC so that is good.

 

I appreciate if you can share your results once you install it - I have a timing belt service coming and will include Fluidampr too if it works.

 

Scubaboo - thank you for the note! Yes, misfire count check on cyls 1-4 were checked, all are 0, idle or not.

 

Thanks a lot,

Ivan (ilib11)

Edited August 5, 2021 by ilib11

[ivan.ej255]

ilib11

 

I forgot to mention that I also had all 4 fuel injectors cleaned last year, they found the injector in cyl 4 to be slightly clogged and dirty. Had them all cleaned then flow tested and it seemed to improve the vibration a TINY bit (still not as smooth as it can be), but it slowly came back after a few days. Most likely it was just placebo that the vibration improved lol.

 

I've been reading about the AVCS as mentioned in your thread in the Liberty forum, and it's something I haven't looked into throughly yet. I'm always including the AVCS angles in my datalogs though and I haven't seen any evidence of AVCS malfunction. I'm gonna dig deeper into this.

 

Regarding the Fluidampr, yes it's mainly for damping those torsional vibrations but it seems like the big side effect of that is a smoother engine overall- at least that's what I can see from Subaru owners' reviews who installed it. I'll post an update when I get it installed.

 

Scubaboo

Yep, mine has 0 misfires too on cyl 1-4, checked throughly by me with romraider and by the dealership with their SSM computer. BTW (Off topic) I forgot to update you but I had the Bilstein coilovers intalled and the ride comfort is WAY BETTER compared to both the OEM Bilstein shocks and the KYB SR shocks lol.

 

Ok back to the topic.

[Scubaboo]

Ilib11, ivan.ej255,

 

That is disconcerting, seeing all you guys have done searching for the problem. I would be logging everything I can and hoping I see a pattern somewhere to explore further.

 

ivan.ej255, congrats on getting the Bilsteins on!

[ilib11]

Thank you, Scubaboo. The full set of logs is in this post http://forum.liberty.asn.au/viewtopic.php?f=18&t=36648#p449755 so everyone please feel free to have a look and make your suggestions. I can do more logs with romraider as required - just let me know what would you like to see.

 

Here is the picture where the problem is well illustrated - the moment AC is ON, RPM drops and the engine runs like it is choked.

Edited August 8, 2021 by ilib11

[Scubaboo]

Nothing jumping out to me at the moment, but I am also wondering about AF correction.

 

How are the actual values/logs of 1st 02 sensor and MAF?

[ilib11]

I can get fresh figures as I already put new O2 sensor and MAF sensors. But I also upped idle to +300 rpm.

 

Edit: here is the fresh log attached. Warm idle, Air Conditioning Compressor Signal (On/Off) indicates when AC is on.

romraiderlog_1111111_20210808_162542.csv

Edited August 8, 2021 by ilib11

[FLlegacy]

Have you guys checked the condition of the engine mounts and transmission mounts the issue may be as simple as increased NVH from a bad mount.

[ilib11]

Hi FLlegacy, engine and trans mounts were checked - found that “RH diff cross member bush leaking” , replaced to the new one and that did not change the original issue at all... Edited August 9, 2021 by ilib11

[ilib11]

To keep the discussion updated - I got a suggestion from another forum:

 

"I wonder if the TVGs could be out of sync. When i was first starting out working on Subarus i made the mistake of taking the actuator off the TVG and had symptoms similar to what you describe. "

 

https://sl-i.net/FORUM/showthread.php?20249-EJ255-Rough-Idle-amp-Engine-Shaking-under-load-like-Aircon-On&p=288665&viewfull=1#post288665

 

Has anyone know how to test these TGVs?

 

Regards, ilib11

[ivan.ej255]

To keep the discussion updated - I got a suggestion from another forum:

 

"I wonder if the TVGs could be out of sync. When i was first starting out working on Subarus i made the mistake of taking the actuator off the TVG and had symptoms similar to what you describe. "

 

https://sl-i.net/FORUM/showthread.php?20249-EJ255-Rough-Idle-amp-Engine-Shaking-under-load-like-Aircon-On&p=288665&viewfull=1#post288665

 

Has anyone know how to test these TGVs?

 

Regards, ilib11

 

Hi, thanks for the update.

 

You can log and compare left and right TGV in RomRaider logger. With my car there is a little voltage variance of around 0.02-0.05v between left and right but I don't think it's enough to make a difference. I will still look into it though, I will thoroughly check on this when I have my car in the shop for AVCS filtered bolts and cam seals replacement.

 

Reading back, I think it's now clear to me that we don't have the same 'problem'. Mine doesn't change with load at all, it's the same with A/C on or off, Drive or Neutral, etc.

 

I think what I'm experiencing is just a little 'nuisance' not really a bad vibration, it's just I don't want to feel that the engine is on at idle as it is with other cars in this class

[tony saurus]

Weird idea but on these cars, have you tried loosening and then retightening all the exhaust flanges?

 

The exhaust can be bound up and cause a seriously weird vibration. Had it happen on a supercharged rs4 cab once and it took forever to track down but it fixed the issue.

 

I know it’s a long shot and assuming exhaust components have been r&i in the period of time where a thermal expansion and binding may occur (I.e. 3 seasons)

 

 

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[ilib11]

Thank you ivan.ej255!

Looks like my Rom Rider does not show TGV - nothing similar in the parameters list.

I use latest Romrider 0.7.2 (2020–11–11) with ECU definitions 0.8.3.1b Oct. 7th, 2009 and Logger definitions logger_v362.

 

Could you please tell how do you see TGV in your rom rider or maybe share some screenshots?

 

 

And if your problem is not related to the load then I think Fluidampr would help you - as you originally suggested.

 

Regards, ilib11

[silverton]

Your car may not be equipped with TGV's, they would be in the romraider list if they were a supported PID. What service did they perform and what kind of technician notes were made?

 

As an aside, with 1/3 and 2/4 being close as pairs, but kind of far range for the group, I have a suspicion that 1/3 is retarded a tooth, but it wouldn't take 40k for that kind of thing to present itself as this roughness you're experiencing.

[ilib11]

I looked to the actual intake and the actuators are there, so I do have TGVs. Not sure why they do not show in romraider.

 

Regarding the service - the dealership performed a standard 'big' service - spark plugs, engine oil change, auto trans oil change, diff oil change. It was not a time belt change.

[ivan.ej255]

Thank you ivan.ej255!

Looks like my Rom Rider does not show TGV - nothing similar in the parameters list.

I use latest Romrider 0.7.2 (2020–11–11) with ECU definitions 0.8.3.1b Oct. 7th, 2009 and Logger definitions logger_v362.

 

Could you please tell how do you see TGV in your rom rider or maybe share some screenshots?

 

 

And if your problem is not related to the load then I think Fluidampr would help you - as you originally suggested.

 

Regards, ilib11

 

Hi, I don't have my Windows laptop with me right now but think it starts with "Tumble" in the parameter list.

[ilib11]

I have found the parameters - they only visible in Romraider if you set Romraider to use SSM protocol, not OBDII. If it gets data correctly, I did not see any changes from the moment of a cold start till the engine is warmed up:

[ilib11]

Problem solved - that were engine mounts.

http://forum.liberty.asn.au/viewtopic.php?f=18&t=36648&start=90#p452529 (link fixed)

 

Thanks everyone for your help and Happy New Year!

Edited January 10, 2022 by ilib11