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Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Tue Feb 02, 2016 12:19 am
by EVL20T
Cant believe no one has a fix yet, i'm having same issues with my 07 GTB EJ25. same hesitation between 2-3k rpm, but it comes and goes like 1 day it will be normal for an hr then problem will start for about an hour, then disapears without even turning off or resetting the ecu

Only thing i havnt done was front O2, AF sensor and clean the EGR

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Wed Mar 16, 2016 9:07 pm
by alexeib7
I previously had hesitation problems with my Liberty 2006 model. I used to reset the ecu by disconnecting the battery cable for about 5 minutes to clear it and reconnect it. The hesitation comes back after a while, but I found an easier way to fix this problem. Disconnect the maf sensor then crank the motor for 3 seconds then turn off, plug the sensor back on then start the vehicle.The engine light will come on, you can purchase a code scanner/ reader cheaply from eBay or buy the Carista app and Bluetooth Obd2 connector to reset wirelessly which is easier than battery disconnection.This method has worked for me so far without hesitation, it could be a faulty sensor but it's a quicker and less troublesome way of clearing hesitation for me.
Good luck you can try this, maybe it will make life easier for you too.

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Tue Jul 26, 2016 9:20 am
by klam
lz2nkm wrote:I'm in contact with the Russian guy Sasha (the one who managed to flash the ECU first). There are some very big thread in Russian forums about the issue and his hypotheses is that the false knock is coming somewhere around the cams - he thinks the noise is from the cams when the AVCS angle is high (above 40 or so) - when I check my logs it goes to 50 degrees on wide open throttle between 2-3k rpm. I asked him what about if we change the OCVs and even the AVCS sprockets but he thinks this is not sure to fix the issue as the noise is coming (according to him) from cams or somewhere there - you know that with this angle the intake/exhaust valses are overlapped and definitely the sound changes. The common agreement among Russian people is that only ECU re-map can solve it once and for all. All the rest is just temporary (soldering capacitor to silence the knock sensor, official ECU update, etc). Maybe only the knock sensor removal (as somebody mentioned here) can also cure it but that is more or less dangerous as it can foul the ECU to pull timing advance which can cause real detonations and this is much worse compared with hesitations. Anyway the Russians just fixing it by ECU flash - Sasha made over 1000 cars in the region and his know-how is spread among other mappers, so there are a lot of people in Russia, Ukraine, Poland, etc. with such re-maps. However nobody there done any extensive verifications to confirm what is the root cause, as it's a lot cheaper just to map the ECU. :) In my opinion on the high levels in FHI they know pretty well what is the problem, but that information is not available outside. Even the dealers does not know it except the service bulletins which in that case says to put 5W30 oil, clean the throttle and update ECU. If somebody have a way to find info from high levels of FHI, then we can eventually know the root cause, but I doubt that info is somehow secret. :)

What was the status with my car? Immediately after I bought it I got the issue (it has 115 kkm on the clock). Then I read here the info and start digging, then bought cable to do myself diagnostic and confirmed I have drop in the ignition timing. Then it fixed itself, and after 200 km made it again but not so bad, then disappeared and appeared again. The last time it was pretty bad with -10.5 knock correction. Anyway, I asked Sasha to tell me if I have all updates and he wanted to send him the ROM (it's possible to download it with USB Vagcom cable) and he told me I have one of the updates but not the last one. He thinks that if the first didn't solved it, then the second cannot help much but it's ok to try, so I installed the last update in Subaru dealer. The car runs fine now for about 1000 km without hesitations. Also after the update I had to reset the ECU as the learning tables for knock corrections are stored in the RAM, not the ROM which they updated. For now I will drive it to see when the hesitations come back (hopefully not soon). Sasha gave me good price for ECU remap (he can even send me ready to plug ecu) and when it start giving issues again I will probably move on with that. What he is basically do is to decrease the AVCS angles from up to 50 degrees BTDC to max 35 degrees (as you can see on the table on my previous post), then he turns off the EGR and secondary air system (if there is one, from MY2008 there is no such) as that is also giving issues. And I think he also do some re-map of fuel maps (probably to make it runs fine without EGR). I read also some feedback for his patch and generally it's good - most of the people report better and smoother torque in low revs, although some slight increase in consumption. Also they continue to confirm all is ok 3 years later. He provide modified vagcom cable which can be used for later upload of updated maps, so some complains can be fixed if it's not ok.

So for me after the tons of info I read, I think the only option we have for final solution is unofficial ECU re-map, since FHI do not care after the warranty finished. That is why they made ECU updates - just to keep the car without complains in the warranty period. Also I can speculate, the other reason is that this problem is not dangerous for the engine (since it retard timing, not advance it) and cannot lead to a lot of broken engines etc., which is worse for their reputation. Everything else is pretty expensive for them, and re-map by doing what Sasha do will probably make the engine ecology worse, which they cannot afford even more (in the context with VW scandal).

this is one great, great write up on the problem and thanks for that. I've tried everything from o2 sensors, oil, throttle cleaning, maf cleaning, OCV's valves changing and the problem was always there and then I just gave up and sent the second hand ECU to Sasha. After his remap and then some fuel remap that was required considering the difference of the petrol 95/98 quality here, the car is perfectly fine and I must report that the fuel economy is actually better, not worse. Previously, I've rarely averaged less than 10.8, currently it's sitting on 10 (pure city driving, occasional hwy). The performance is great given it's a 2.0l NA engine and it's a wagon.

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Tue Jan 30, 2018 9:09 pm
by EMark
Hi guys,

I have a Subaru Legacy 2.0R from 2006. And like all other owners of a car with such an engine I also have problems with a flat spot between 2000 and 3000 rpm.

I have read a lot about this problem, in this forum, in other australian forums, few forums and blogs from UK and Europe. All this engines have this problem, all without exeptions. I have read about many different attempts and approches for fixing the issue, but without results. I'm familiar with the method of the russian guy Sasha to solving the problem. I have read about disconecting of the knock sensor as well, and other things like that. But I think all these solutions to fix the problem are just workarounds. Some theories say that the problem is in the AVCS valves, other that the problem is in the ECU, or in the mapping tables, but non of these are proven or certain. I know about few owners which have changed the AVCS valves but without result for example. I don't believe that the ECU has a hardware or software problem as well.

But there is one thing which is questionable, and I didn't read whether someone has doubted or assumed it - everyone looks for the problem in various details, but not in the engine. It is obvious that (even with a new knock sensor) there are knocks, and the ecu retracted the ignition advance upon this reason. Probably the problem is not in the ECU, or in the sensor, or the valves but in the engine itself.

It could be worn main bearings of the crankshaft. Does anybody check this? Because I have experience with different car and engine but with the same problem, and the problem was in the main bearings of the crankshaft. After changing the bearings the problem dissapeared.


Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Mar 10, 2018 9:16 am
by DracoKn
Hi everyone,
I recently bought a 2006 Liberty 2.0R, at point of purchase I wasn't aware of the common hesitation issue with the car.
The car has been in and out of mechanic a few times because the throttle sometimes would not respond when it's cold started and the engine hesitates for a second or two at 2000rpm before it takes off.
As far as I know the mechanic has put in new spark plug fuel filter, replaced a split fuel pressure regulator, and cleaned air flow meter, and I was told there was no problem with the other sensors Every time I got the car back it drives really well, but the problem start to come back after a few days. I find that every time the problem comes back I can just disconnect the ECU and the car drives well again, which makes me think that it's not really a problem with the components but the ECU itself.
I really appreciate if anyone can share some insights to help me with alleviating this headache.

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Oct 06, 2018 11:34 pm
by JiPe38F
Hi gals and guys

I live in Grenoble, France. So be kind with my schoolish english... I purchased recently a Subaru Forester 2.0 l atmospheric, with 4EAT automatic gearbox. 2007 model 160 mkm. Nice car, I like it when it runs correctly, which is not the case most of the time. I had an issue with the auto gearbox : fault code, "power" lamp flashing. I finished to understand that there is a leak in the torque converter clutch (which cancels the slip when rmp is above a threshold in 4th gear). Torque converter to change... Some say that this issue could be caused by a too high oil lever in the gearbox, which creates spikes of oil pressure. Thanks to the guys (subaru ?) which serviced the car before I bought it.

I have another issue. Some times, more and more frequently, under 3500 rmp, my 158 hp forester behaves like the first car that I drove, decades ago, a Citroen 2cv : a vintage flat twin with 600 cm3 engine and 20 hp ! You can imagine the fuss with an auto gearbox : if it arrives in 4th gear, I accelerate, which makes the gearbox to shift down to 3re gear, the rpm go over 3500, and then my car accelerate like a dragster, until I release pressure on my foot, the gearbox shifts up to 4th gear, and so on ! WTF as would say your cousins from over the pond ! I began changing the ignition coils, resetting the spark plugs to 0.8 mm gap (they were nearly ok). Same as you said, everything went correct for a few km, time for the ecu to learn the engine parameters, and again the problem...

Lurking here and there on the net, I ended coming on your forum and this thread. Great ! I think you got the cause of the problem. I have read the "romraider" thread on the subject, with the solution proposed by Sasha in Russia. Now, let me add my two cents to the discussion.

Just a word about my personnal history. In a previous life, as was a robotics engineer. So I had to cope with some hydraulic robots. Fact is that sometimes, these machines get a parkinson-like behaviour, their hands shaking like those of a person with this deadly disease. Most of the time, the cure is simple : flush the oil off, clean the oil circuit, refill, purge air bubbles, and everything goes smooth again. The reason is that there are close loops including software - electronics - hydraulic valve - hydraulic cylinder (linear or rotating) - position sensor and, when oil gets old and/or dirty or when there is air in the hydraulic circuit, the loop characteristics change, which brings the closed loop to unstability.

Well, a bell rang in my brain. How does a acvs work in my EJ204 engine ? On the front of each intake cam shaft, the pulley contains a rotating hydraulic actuator, with a 50° angle range. It is fed with oil through an hydraulic valve, which is commanded by the ecu. In order to give the right advance angle to the shaft, the ecu reads a position sensor on the back side of the intake camshaft. I suppose that it calculates the difference beetween the angle measured by this sensor and two times the angle of the crankshaft, also monitored with a sensor. This value gives a measure of the hydraulic actuator's position, from 0° to 50° inside the pulley. The point to understand here is that this works as a position closed loop, like in the hydraulic robots ! You see where I'm coming to ?

I think therefore that when the oil gets dirty, the hydraulic circuit beetween the hydraulic valve and the pulley gets clogged with shavings from the engine wear, or if the oil pump introduces some air bubbles in the high pressure oil pipes, the closed loop characteristics get out of normal range, and the loop gets unstable. If the angle value is in mid range, the parkinson oscillation of the actuator inside the pulley can be unnoticed. But, if the angle value is around the maximum, this oscillation can cause the hydraulic actuator to get into mechanical limit, which causes a shock (steel on steel impact, brutal oil pressure spike). Now, the reason given by Sasha, our russian expert, that this shock is interpreted by the ecu, through the click sensor as "too much ignition advance", giving as a consequence a change to "retard ignition", this not modifying anything and... ultimately the ecu getting to maximum lag ignition delay, seems to me a good logic path. As for my car, giving the loss of torque on the engine, Citroen 2cv like behaviour, and some rattle noise which my wife once remarked, asking "why does your car make this noise ?" !

So, what are, in my opinion, the fixes for the problem ? I think that I will concentrate my efforts on the closed loop of the avcs system. First, change the oil in my car. It's true that it's getting more or less dirty now. I have seen worse on other cars, but now I understand that I must keep it super clean. I will fill it with 5w30 grade, as now, ignoring the risks, I used standard 5w50 to complete the oil level. If this doesn't fix the issue, I will open all the hydraulic components of the closed loop : pulleys on the intake camshafts, electro-hydraulic valve, clean all this, flush a detergent liquid inside the circuit, get off the steel shavings with a magnet. I will also open the crankcase under the engine (I hope it's possible...), clean all the crap inside it, see if there is a magnet with steel shavings stuck on it, get them off. Ultimately, if this is not enough, I will think of an issue that I had with a motorcycle : the ignition position sensor was an hall effect sensor. Taking it off, thinking it was to change, I discovered that it had steel shavings stuck on it by magnetic effect. I just cleaned it and put it in place again, and the bike got a nice engine run with super accelerations ! I can do it on the position sensors on the intake camshafts and crank position sensor.

Nice program, isn't it ? I was thinking of changing the torque converter, which implies to separate motor from gearbox : some say that on subs, the easiest way to do it is to take the engine out ! Well, once the engine is out, it should be easier to do all this service to the avcs loop, isn't it ? What do you think of my servicing program, guys and gals ?

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Wed Oct 24, 2018 3:32 pm
by bigBADbenny
Spot on! However I’d target the easy stuff before pulling the whole lot.
Perhaps wait for a timing belt service.

I can say one intriguing thing I’ve noticed with my 2.5t inlet ocv’s: after a year or two of running replacement ocv’s without issue, I noticed that the lag between logged vvt angles started to increase a little.

I use megalog viewer to analyse my Btssm logs, this allows me to make a custom parameter that subtracts one vvt angle from the other, meaning perfect sync is 0 and imperfect sync is a + or - value.

As regards my heuristic solution, I simply swap the ocv’s side to side every year or when I see excessive lag appearing.
That’s also the basic sanity check or test for ovc functionality.

Perhaps the closed loop avcs calibration begins to overdrive the solenoids as they naturally begin to wear in use.
Certainly there are differences in the oil feed supply locations that may influence duty in use.

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Jul 13, 2019 5:58 pm
by wildfire42
Hi all,
Any update on the hesitation issue ?
I bought a 2007 30R wagon about a month ago and it has just developed the hesitation.
Disconnected the battery and now all good - runs well and accelerates smoothly.
If disconnecting the battery fixes it then I doubt that the cause is a sensor.

It has to be an ECU problem with its "learning" operation and when it goes back to factory
settings after battery disconnection all is good again till it "learns" crap and screws up.

It would be good to be able to compare the factory maps in the ECU with the "hesitation maps"
and see what has changed. Unfortunately I don't have the resources to do that.

Looks like I will be resetting the ECU every time it happens :-(

Any opinions on this ?


Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Jul 13, 2019 6:38 pm
by bigBADbenny
Yes, what you want to look at is a Learning View.
That’s essentially a graphic of the ecu’s learned values or corrections made for self preservation.
Something that’s out of spec, and the ecu attempts to correct aspects of the tune to compensate.

The actual causes are related to the air, fuel, fire triangle eg airflow in the inlet tract, compression and exhaust; fueling including closed loop operation; spark and ignition timing etc.

You can make an LV using Btssm or Romraider, I can do both in melbourne.
Doing so may give a rough idea of where the issue might be found.

Otherwise you’re limited to basic tests like reading the spark plugs, pressure testing the inlet and exhaust, inspecting the catalysts etc.

You can read about LV specifics in my tune faq link in my signature below.
There’s a diagram that explains the learned values,

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Jul 13, 2019 6:42 pm
by bigBADbenny
Using a basic scan tool will also allow you to read check engine lights aka CEL’s aka diagnostic trouble codes/DTC’s.

The FSM (links below too) has diagnostic trees for DTC’s too.

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Jul 13, 2019 6:54 pm
by wildfire42
Thanks Benny. Super quick reply :-)

Looks like I have "learning" to do so I can understand what is happening.


Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Sep 14, 2019 10:54 pm
by paulc
Hi guys, I'm a newbie here

Could someone tell me what the max Knock Correction value should be for a year 2000 2.5l Outback
I'm getting up to -10.5 while driving and reving the engine (more than 1900 RPM)
The following forum says:-

b.) AT (Automatic Transmission)
Drive the vehicle for 20 minutes to stabilise engine operation and temperature.
Connect the SDS and conduct 3 stall tests allowing 2 minutes at engine idle between each test to reduce ATF
temperature. View the SDS knock correction data in relation to the table below;

Maximum Knock Correction Stall speed if AT Comment
Up to –4 Degrees Up to 2400 RPM Engine is performing normally
-9 and greater (-10, -11, etc) 1900RPM and less Report via FPRS to Subaru (Aust.)Technical Dept.

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sat Sep 14, 2019 11:31 pm
by bigBADbenny

Are you on top of the maintenance?

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sun Sep 15, 2019 12:29 am
by paulc
Hi bigBAD,
I meant the most negative value ?
It’s a 2000 Subaru Outback Limited 2.5l auto that’s done 300K km
The car has the dreaded hesitation/flat/surging problem without having EGRs or OCV’s
It’s seriously dangerous to drive because it will fail to accelerate and then take off
I’ve had the car for 10 years and I had the timing belt go about 4 months ago
It was a bit flat after changing the belt but it has gradually got worse
Everything ? has been changed
TPS, MAP, knock sensor, coil, ballast resistor, leads, plugs, O2s, eng temp, crank and cam sensors
Everything ? has been checked by Subaru mechanics
Timing belt, compression test, leak down test, thermostat, radiator and fuel pressure tests
Everything ? has been cleaned
Throttle body, idle control vlv, PCV, intake manifold and upper cylinder cleaner
It runs better if unbolt the knock sensor and tie it back
It runs better with octane additive in the tank
I’ve changed from Caltex to Shell 98 fuel
I’m using freessm to monitor the key parameters
There are no error codes
I reset the ECU before each test
I’ve noticed that the tacho readings are a little jumpy
I’ll check the AT fluid level and stall test the torque converter
Any thoughts ?, change the ECU ?

Re: Engine hesitation/flat spot (Liberty 2.0R)

PostPosted: Sun Sep 15, 2019 9:38 am
by bigBADbenny
That sounds like expensive parts cannon action, for an engine that has an almost agricultural level of simplicity. ... 28/engine/

I'm not really an expert in especially gen3's, but as you say, increasing octane and taking the knock sensor out of the loop are big clues.

Got a brand new maf in there?

Have you confirmed there's no inlet or exhaust leaks?

Post a link to a log with your tuning parameters and the issue, a huge log is fine.

But dont log immediately after an ecu reset, better after 30klm of steady driving.

Have you tried the ol full circle grounding kit? ... way.25717/

Have a dig in here too, posts re grounding scheme inc inlet mani/fuel rails.