Rough Idle & Engine Shaking under load like AC

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Re: Rough Idle & Engine Shaking under load like AC

Postby Stifull » Sat Dec 19, 2020 8:38 pm

LOL.. Yes.. We have had many subarus for many years. We currently have 5 in our household. We have NEVER taken ANY of them to a dealer except for airbag recalls and true to form they damaged the dash on my Lib GT in the process...Great product...but never take it to them for service or repairs..We only take them to Subievolution when it's something we can't do ourselves. They do an awesome job. I think Russell spoils us because we have soo many .
Current Subarus
07 Liberty GT (mine) 180kwt on 16lb
98 WRX Club Spes 2 with 2.5ltr upgrade(mine) sub 14 sec
99 Ver 6 Sti also with 2.5ltr upgrade (son) sub 14 sec
02 WRX Bugeye Hatch lots of goodies(wife)
09 Non Turbo Impreza(daughter#4)
Previous
98 GC8 WRX Hatch(daughter#1)
02 Bugeye WRX (daughter#2)
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Sat Dec 19, 2020 9:48 pm

Hi All,
Thanks for all the hints!
In addition to leak tests, I'll ask to examine spark plugs too.

Re air filter: the air filter has been changed to a new one, installed ok.

Re MAF - First I did I took it out myself and cleaned it with a CRC MAF spray - as I usually do on a regular basis. That did not resolved the issue. O-ring looks ok, and MAF sits tight.

Re upper engine clean - I cannot tell if it was actually done. I saw stories on Whirlpool about subi services which just do not do that to save time/effort and throw out these upper clean chemicals cans. Where would you connect in 2.5T intake to do the upper engine clean?

Re spark plugs torque - may I kindly ask on how the spark plugs torque make a rough idle? On any other cars I had I did not have any problems by just screwing in spark plugs hard enough. These engines were not boxers though.

Thanks and regards, ilib11
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Re: Rough Idle & Engine Shaking under load like AC

Postby bigBADbenny » Sun Dec 20, 2020 3:39 pm

ilib11 wrote:Re upper engine clean - I cannot tell if it was actually done. I saw stories on Whirlpool about subi services which just do not do that to save time/effort and throw out these upper clean chemicals cans. Where would you connect in 2.5T intake to do the upper engine clean?

Re spark plugs torque - may I kindly ask on how the spark plugs torque make a rough idle? On any other cars I had I did not have any problems by just screwing in spark plugs hard enough. These engines were not boxers though.


UEC: see the seafoam link in my tune FAQ (link in my signature), usually the BOV ref hose on a turbo car, wrap the straw in tape to get a good seal on the hose.

Sparkplug TQ is definitely a factor, misfires are calculated from discrepancies in crank vs spark timing plus afr.
I'm not sure exactly what triggers the cel in this instance, could be compression related?
Last edited by bigBADbenny on Thu Dec 24, 2020 12:08 pm, edited 1 time in total.
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Sun Dec 20, 2020 5:05 pm

Thank you, adding UEC to the list of actions....

FYI - Here is what I found for misfires - page GD(H4DOTC)-95 in the attached file describes the algorithm - as I understand, a misfire would change immediate crankshaft speed so that is now it is detected.
The file is from 2010 Subaru Legacy and Outback Factory Service Manual. I am pretty sure you have it, or let me know if not and would like to have :)
Attachments
2. Diagnostic Trouble Code (DTC) Detecting Criteria.pdf
(842.27 KiB) Downloaded 108 times
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Re: Rough Idle & Engine Shaking under load like AC

Postby bigBADbenny » Sun Dec 20, 2020 7:51 pm

If that’s a general market/adm GenV FSM absolutely I’d like the link to add to the list.
I’ve not found one yet online, only usdm :)

Did you invest in your own Romraider setup with Tactrix or vagcom?
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Sun Dec 20, 2020 10:49 pm

This particular one was USDM from here: http://jdmfsm.info/Auto/Japan/Subaru/Legacy_Outback/2010/ There are bunch of other stuff both for Subaru, other cars and relevant info on that site.

Yep, I have a laptop with romrider and a vagcom cable. I did have a chance to work on some fun cars & engines ( VW Corrado & Passat, G60 Syncro) in my previous life but do not have a workshop place & toolsets anymore :(
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Re: Rough Idle & Engine Shaking under load like AC

Postby bigBADbenny » Mon Dec 21, 2020 5:00 am

Yep I’ve been using that site a lot, linked in the faq.
Some of the gen4 FSM’s there are “live” as well, that is direct access from a browser, but not the GenV FSM’s alas.
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Mon Feb 22, 2021 4:23 pm

Hi All,
just an update on this problem...
Went to a service for a searching for leaks and nothing found. As a workaround, increased idle RPM so it is >=800 under load (Auto Trans at R, A/C is on). At least that masked the problem and the shaking is not that violent (but still exists).

Reading the forums, bumped into the following https://forums.nasioc.com/forums/showpost.php?p=44412059&postcount=31 - which could be another theory to test, even if I do NOT have P0340 code:
"it appears that indeed, a bad alternator can truly cause the P0340 code. apparently a bad diode or voltage regulator sends a noisy signal through the harness and the cam sensor reads this as a fault. So anyone experiencing this code and has the primary symptoms of momentary rough idle especially when the AC is turned on, please check the alternator. it may appear to be sending proper voltage or even pass testing, however internally its faulty ".
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Mon Apr 12, 2021 4:38 pm

Hi All,
The next update on the problem in case you are interested....
The car is no better so I decided to fire a small parts cannon and also did some extra tests.
1)I took an oscilloscope and checked voltage from the alternator - all stable, no noise, dropping or other obvious abnormalities.

2) Measured cylinder compression with open throttle :
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)

3) Changed the plugs to new NGK Ruthenium HX LFR6BHX. The old ones from the dealership were NGK SILFR6B8 (no Subaru marking or other identification), but looked good to me. There was a sort of silver grease on their threads, looks like it was an anti - seize.

Old_spark.JPG
old spark plugs
Old_spark.JPG (200.94 KiB) Viewed 2004 times
New_Spark.JPG
new spark plugs
New_Spark.JPG (53.83 KiB) Viewed 2004 times


4) Changed ignition coils on the cylinders 3 and 4 to new Subaru genuine ones. (Did not change them on 1 and 2 as it was a small parts cannon :) and I already cleaned coils earlier for cylinders 1 and 2 and swapped them from 1 to 2 and vice versa with no positive effect). Old coils were dirty with some white residue at the spark plug side.

5.JPG
old coils 1
5.JPG (229.43 KiB) Viewed 2004 times
6.JPG
old coils 2
6.JPG (235.42 KiB) Viewed 2004 times


And the results are as follows:
- Idle got smoother for sure
- acceleration (I think) is better too and it has a more delicate or smooth sound
- the initial problem with shaking under load did not go but become reasonably better. And I was able to reduce the rpm upping from +200 to + 150 rpm.


I think I will continue with replacing the other two ignition coils and see what happens.
The compression difference of 1 bar across cylinders - is that too bad or within normal limits?

Thanks and regards, ilib11
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Fri Jul 23, 2021 4:19 pm

Hi All,

After a number of investigations 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


Other checks:

- 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 :
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)


Unfortunately I still cannot fix the original issue and I am practically out of ideas what else could be a reason for it, that drives me nuts. Only the following two left in my mind:

a) something strange with injectors which makes uneven fuel supply at low rpm
b) banjo bolts are blocked with some gunk so it is not enough oil pressure for AVCS etc at low rpm



Are there any ideas for the next steps?
Please share, I would appreciate your input, thank you!
ilib11
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Sat Aug 14, 2021 10:30 am

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
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Re: Rough Idle & Engine Shaking under load like AC

Postby bigBADbenny » Sun Aug 15, 2021 4:53 pm

The man, the myth the legend, Lord Flashheart!

Tgv position is calibrated and actuated by the ecu, like dbw & avcs.

As such any malfunction or disconnection cause a cel/DTC unless deleted in the tune and at the intake manifold :)
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Re: Rough Idle & Engine Shaking under load like AC

Postby bigBADbenny » Sun Aug 15, 2021 5:19 pm

Intake manifold gaskets are a primary suspect.
When 2.5i owners remove the intake manifold the they’re often falling to bits due to degradation of the composite gasket material.

To test unobtrusively, use inlet pressure engine not running, or with vacuum, engine running.



ilib11 wrote:Hi All,

After a number of investigations 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


Other checks:

- 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 :
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)


Unfortunately I still cannot fix the original issue and I am practically out of ideas what else could be a reason for it, that drives me nuts. Only the following two left in my mind:

a) something strange with injectors which makes uneven fuel supply at low rpm
b) banjo bolts are blocked with some gunk so it is not enough oil pressure for AVCS etc at low rpm



Are there any ideas for the next steps?
Please share, I would appreciate your input, thank you!
ilib11
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bigBADbenny
 
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Re: Rough Idle & Engine Shaking under load like AC

Postby bigBADbenny » Sun Aug 15, 2021 5:24 pm

The factory service manual should have compression specs.

The difference in pressure might be attributed to valve clearances.
Iirc the test for that is if you’re unable to reach sufficient inlet vacuum at idle, assuming other health checks and tested vacuum.

Diagnose with obdii logging or external gauge connected to intake manifold…

ilib11 wrote:Hi All,
The next update on the problem in case you are interested....
The car is no better so I decided to fire a small parts cannon and also did some extra tests.
1)I took an oscilloscope and checked voltage from the alternator - all stable, no noise, dropping or other obvious abnormalities.

2) Measured cylinder compression with open throttle :
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)

3) Changed the plugs to new NGK Ruthenium HX LFR6BHX. The old ones from the dealership were NGK SILFR6B8 (no Subaru marking or other identification), but looked good to me. There was a sort of silver grease on their threads, looks like it was an anti - seize.

Old_spark.JPG
New_Spark.JPG


4) Changed ignition coils on the cylinders 3 and 4 to new Subaru genuine ones. (Did not change them on 1 and 2 as it was a small parts cannon :) and I already cleaned coils earlier for cylinders 1 and 2 and swapped them from 1 to 2 and vice versa with no positive effect). Old coils were dirty with some white residue at the spark plug side.

5.JPG
6.JPG


And the results are as follows:
- Idle got smoother for sure
- acceleration (I think) is better too and it has a more delicate or smooth sound
- the initial problem with shaking under load did not go but become reasonably better. And I was able to reduce the rpm upping from +200 to + 150 rpm.


I think I will continue with replacing the other two ignition coils and see what happens.
The compression difference of 1 bar across cylinders - is that too bad or within normal limits?

Thanks and regards, ilib11
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bigBADbenny
 
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Re: Rough Idle & Engine Shaking under load like AC

Postby ilib11 » Sun Aug 15, 2021 7:41 pm

bigBADbenny, thank you for keeping an eye on this topic!

Re compression : Service Manual says - 142-171 psi, difference is 7 psi or less. My figures are slightly off these but the engine was not hot at the time of measurement.
so I got compression slightly below normal and the difference twice more than advised by the manual. Giving the engine is not new (160K), would these measured figures cause any concern from the practical point of view? What would real experience say? Like if I see one cylinder has a compression twice less then others that would definitely say there is a problem, would a slightly degraded compression be a concern? (note - engine has practically no oil consumption and does not require adding oil between changes)

Re vacuum: as per specs ( at least 19.7 in Hg on idle AC Off)
I noticed none of these conditions which also listed in the service manual:
1. Needle is steady but lower than standard value. This tendency becomes more evident as engine temperature rises +> Leakage around intake manifold gasket, or disconnected or damaged vacuum hose
2. Needle intermittently drops to position lower than standard value. => Leakage around cylinder
3. Needle drops suddenly and intermittently from standard value. => Sticky valve
4. When engine speed is gradually increased, needle begins to vibrate rapidly at certain speed, and then vibration increases as engine speed increases. => Weak or broken valve springs
5. Needle vibrates above and below standard value in narrow range. => Defective ignition system


Re gaskets - degradation of the composite gasket material: I got new sets, they either silicon ( TGV "binoculars" - Intake manifold ) or sort of a thin "cardboard material" ( cylinder head- TGV "binoculars" ), I thing you are talking about the "cardboard" ones. I tried to establish a leak there by using a lot of carb cleaner and /or butane gas - no leak found. SubiEvolution looked there too and did not find anything. So I think the only I can do next is to disassemble everything to get to these gaskets and replace them.

Re TGV: I have read people get these TGV removed and get simpler system and extra power, at least for previous years Subarus. I noticed the design is slightly different from the previous years - there is no separate TGV position sensor, looks like it is combined with the actuator now. Is that possible to remove TGVs for this 2010 model? Is that a common/recommended mod? ( I am thinking that if I need to disassemble the intake to check/fix gaskets, it may be good to remove these TGVs at the same time and save some effort).

Re TGV and idle: https://www.romraider.com/forum/topic360.html says that TGV could be related to idle:

Base Timing Idle (In-Gear) - This is the base timing in idle mode when the transmission is not in neutral. Although the map switching between A and B is not entirely understood, it appears to be related to the TGVs.
Base Timing Idle (Neutral) - This is the base timing in idle mode when the transmission is in neutral. Although the map switching between A and B is not entirely understood, it appears to be related to the TGVs.

As the original problem relates to idle , and especially is worse in gear ( a sort of load), I could thing this TGV lead is worth investigating.


P.S. Sorry for all these questions if there are too many of them.. I have to admit I am at the edge of my capabilities - I have no workshop so unable to lift a car, extract the engine from it etc. by myself. And the car has been in a reputable service with no obvious leaks/faults found. I simply would like to see a way forward from where I am now.

Kind regards,
ilib11
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