EJ255 - 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 (used multiple stations, typically 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 Idle RPM settings as + 200/300 rpm via Rom Rider, but that only reduces the symptoms to some extent, not a fix.

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

Regards,
ilib11

[lord flashheart]

Sorry for a late reply.

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.

[mike-tracy]

The man, the myth the legend, Lord Flashheart!

[lord flashheart]

The man, the myth the legend, Lord Flashheart!

yeah, I've been gone a little while, but ill (hopefully) be around.

[ilib11]

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.

Thank you lord flashheart ,that is a very useful info ! Am I right that TGV is something that I marked red in the picture below? I do not know much about TGV - if you know, could you please tell how I can test them?

Thanks a lot, ilib11

[lord flashheart]

That is correct. That is the TVG actuator. We fixed my car because i worked at a shop that had one of those super advanced snap-on OBDII reader deals. I wonder if some open source tuning would give you information about the TVG data. I'll check alldata and see if they have any way to diagnose without a one of the fancy computers, and post up if i find anything.

[ilib11]

I have found the parameters in Romraider - they only visible 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:

[lord flashheart]

I have found the parameters in Romraider - they only visible 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:

hmm, that's strange. can you post a video of the problem?

[ilib11]

I do not have a video at the moment, will do soon. This picture though illustrates the problem - on idle, at the moment AC is ON, RPM drops and the engine seriously vibrates and runs like it is choked. Then RPM is increased and the engine recovers. Next time AC is ON (or actually any other extra load added such as the auto transmission put on Reverse) the situation repeats itself.

The full set of logs is in this post http://forum.liberty.asn.au/viewtopi...=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.

[ilib11]

Hi All,

Meanwhile I have done more logs & Learning View screenshots under different conditions.
They cover the following:
-warm up,
-Idle with added load,
-normal driving (2 pcs with standard and extended set of logged parameters)
-gentle braking.

The logs and their descriptions are here : https://mega.nz/file/kfYFRApS#F6vwwd...7TN78BVgGWr4UA


I also made a couple of videos here - it is engine on idle with aircon ON/OFF. At the time of the video the engine has no added RPMs in User Defined RPM Settings and it is vibrating. Once AC is ON you can hear the engine tone changes and you can notice an extra vibration.

https://mega.nz/file/YPAx2SyY#TatjOA...vTstdZZGjyjniY
https://mega.nz/file/wTJTVKaR#8OjITP...bPfRokYzmatt3w

[lord flashheart]

The video helps, because this is different than what I was imagining.
I was sort of imagining it running like it was down a cylinder but the video makes it look like it runs fine until you turn on the a/c.
Another thought, you said it drives well, no issues? I'm wondering if the issue could be related to the AVCS. I can't remember how good or bad the computer is at picking up when the AVCS actuators are out of phase. It seems reasonable to me that if the avcs was slightly advanced (as it should be at higher rpm) it would run fine in upper RPMs but idle like shit. they have been know get stuck. i know there is a code for over advance on those but i don't know what the threshold is.
anyways, just thinking out loud.

[ilib11]

Problem solved - that were engine mounts.
http://forum.liberty.asn.au/viewtopi...452529#p452529

Thanks everyone for your help and Happy New Year!

[mike-tracy]

Thanks for the update. I'm glad it was a simple fix after all that time