Engine hesitation/flat spot (Liberty 2.0R)

[dmh87]

I'm occasionally experiencing the same problem as well.. I've noticed that the petrol can make the difference, though not much.. I'm not really happy with the fuel consumption neither and I reckon it might have something to do with some of the sensors... As my cruise control light and CEL came up lately, reading through forums makes me believe the problem is in the sensor(s), but not sure which, I'm not the mechanic type of guy really so pardon me my ignorance

so what options we have in order to improve the performance so far?
A) trying different petrol,
B) cleaning the MAF sensor,
C) updating the ECU (?),
D) installing after market exhaust (?)

add
a) tried, made a slight difference
b) can one do it itself? any instructions anywhere?
c) who around Sydney can do this? Subbie dealers only?

thanks!

Has your O2 sensor ever been replaced?
My CEL came up a while back, and it was diagnosed that the o2 sensor had let go and needed replacing. After it was replaced it was ran perfectly fine.
As for the ECU update of that hesitation problem, most Subaru dealerships are able to patch it for you - not too sure on costs though.

[Kormoran]

I'm occasionally experiencing the same problem as well.. I've noticed that the petrol can make the difference, though not much.. I'm not really happy with the fuel consumption neither and I reckon it might have something to do with some of the sensors... As my cruise control light and CEL came up lately, reading through forums makes me believe the problem is in the sensor(s), but not sure which, I'm not the mechanic type of guy really so pardon me my ignorance

so what options we have in order to improve the performance so far?
A) trying different petrol,
B) cleaning the MAF sensor,
C) updating the ECU (?),
D) installing after market exhaust (?)

add
a) tried, made a slight difference
b) can one do it itself? any instructions anywhere?
c) who around Sydney can do this? Subbie dealers only?

thanks!

PAK update is $149.

But firstly, find out what the code is If its the o2 sensor all your problems could be related to that.

Try some Upper Cylinder Cleaner, I noticed when I did mine the other day (Shot it straight into the throttle body, not through a vacuum hose) and because the car was on a slight angle, some cleaner flowed back out and it was black. It was serviced less than 3 months ago and I watched them put it through so maybe there is still some crap in there as there certainly was in mine?

As for fuel BP Ultimate seems the way to go.

Definitely clean the MAF too as you never know.

[klam]

Has your O2 sensor ever been replaced?
My CEL came up a while back, and it was diagnosed that the o2 sensor had let go and needed replacing. After it was replaced it was ran perfectly fine.
As for the ECU update of that hesitation problem, most Subaru dealerships are able to patch it for you - not too sure on costs though.

as long as I have it I haven't changed the sensors, just the major service been carried out (timing belt, spark plugs, water pump, radiator, plus generic stuff). How much was the o2 replacement and where did you get it serviced?

[klam]

PAK update is $149.
But firstly, find out what the code is If its the o2 sensor all your problems could be related to that.
...
Try some Upper Cylinder Cleaner, I noticed when I did mine the other day (Shot it straight into the throttle body, not through a vacuum hose) and because the car ...

Definitely clean the MAF too as you never know.

thanks for all your help man... Yep, while having the major service, the ucc was used to give an engine a bit of a cleanup. ran nice and smooth afterwards, but not for long though. Will get it some diagnostic tests to see what is actually wrong.

[Kormoran]

Not a worry, happy to help. If you work out something that I am yet to try, let me know as the hesitation occasionally returns for me still. Cheers

[dmh87]

Definitely clean the MAF too as you never know.

+1

as long as I have it I haven't changed the sensors, just the major service been carried out (timing belt, spark plugs, water pump, radiator, plus generic stuff). How much was the o2 replacement and where did you get it serviced?

I replaced my o2 sensor a while back so I don't quite remember the price, don't quote me for this but I remember it being somewhere around $250.
You could try and give Garage 88 a call, I know that they stock the o2 sensors but not sure whether or not for your specific model.

[klam]

This is what I stumbled across on some other forum, might be worth of having a look at the butterfly maybe? ... just a thought. have a great holiday guys.

"I asked my Subaru Mechanic how they used the UEC and he said they put 1/2 a can into the engine via the the throttle body and then let it sit (like you do with oven cleaner), whilst it is sitting they use a toothbrush to scrub around where the the butterfly sits as it gets a build up of gunk around there, this then stops the butterfly from seating properly and it can cause a mix of minor problems that you may think are being caused by a major part ie. the IACV - MAF - MAP etc.
He said the same thing can happen with the gearbox Neutral Switch and after mine was swapped out Thursday I can certainly say I can feel the difference."

[klam]

Managed to run diagnostic, the only error number logged was P0030, which points to the o2 sensor's heating issue. Will reset the code and check occasionally till it comes up again, if so I'll change the front o2 sensor (hopefully it will help the fuel consumption a bit too). Meanwhile I'll clean the MAF sensor and run UEC through the throttle. That's the most I can do, if it won't help the occasional flat spot issues I'll just sell it and get another car.

[Kormoran]

Bought a new air/fuel ratio sensor from Garage 88, fingers crossed.

[klam]

good luck with the new sensor, just make sure you have the correct number. I was given a wrong number by denlo subaru, instead of front af sensor (22641AA38) I was given a part number for the rear one (22690AA970) and figured it out by sheer luck. How much it is from garage88? I'm still waiting for the quota.
also' ran the diagnostic, but I cannot get to plot the a/f sensor values.. could you please provide some 'how to' info. the values from the lambda sensor should be more the sinus line while engine running on idle.
cheers

[Kormoran]

Cheers, the guy who answered when I rang Subaru didn't seem too pleased when all I asked for was the part number! Garage 88 gave me a great price, definitely email them again, I got a quick reply.

Im not sure to be honest, I use a bluetooth OBD adapter and android with Torque Pro and just looked through what was available and air fuel ratio (measured) popped up. Decided to log it and the parts where it gets high is when I've accelerated I am only starting to learn about it myself.. sorry mate.

[LOWLIB]

koromon,

has your hesitation come back yet? im getting a bit over mine an having to reset the ECU after doing all the other possible things to it and am consideirng just forking out for the map update

[Kormoran]

koromon,

has your hesitation come back yet? im getting a bit over mine an having to reset the ECU after doing all the other possible things to it and am consideirng just forking out for the map update

Sadly yes, and now I have no idea why anymore. (all my theories were busted)

[LOWLIB]

koromon,

has your hesitation come back yet? im getting a bit over mine an having to reset the ECU after doing all the other possible things to it and am consideirng just forking out for the map update

Sadly yes, and many times But I think I narrowed it down to the a/f ratio sensor.. I stopped resetting the computer so I could 'try' and log it with torque.

What I think is going on (not 100% of course); af ratio sensor is on its way out making the car to run too lean, it then cuts timing resulting in the noticeable flat spot and a lack of power throughout the rpms... (screenshot in a post above)

Ill know in a week or so at least, when my sensor arrives from G88

awesome mate. can you post up some results afterwards once you have the new sensor and let me know? because mine has become a bit more common of late im not sure if it is the sensor dying more or if it is the hot weather in queensland.

[Kormoran]

Will do. It should be here next week hopefully!