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EJ251 loss power, stall fault catalyst/O2/Air flow/IACV

scalman

Forum Member
Joined
Dec 1, 2017
Messages
2,552
Location
Lithuania
Car Year
2006
Car Model
2006 3.0R 5EAT Sportshift VDC/VTD LPG
Transmission
5eat Sportshift
so things continue as this or similar from when i bought car.its about for 2 yrs now. i changed spark plugs, wires, petrol filter , LPG filter , air , oil changing as supose too and diff oils too. but from beggining i have some kind of power loss or lagging when wanna accelerate from stop. sometimes it goes fast and sometimes it thinks 1,2,3 seconds just then moves.

i was reading what could cause that and such , was cleaning all intake parts and valves that can be cleaned there.

i am getting just P0420 code what says bank1 error. so it kinda O2 sensor , but does front sensor can cause power loss , stall sometimes from no reason and lag in acceleration ? its sounds more like air flow mass sesnor , or IACV . and then could that be bad catalyst. but again would catalyst cause all those symptoms ?

so i cleand IACV maybe 3 month ago. it was not so bad , but i cleaned it anyways and other valves and sensors too that people say in net could cause suchs problems. but just today my call stall in middle road. but then i stopped fast , put on P start engine again and it went as if nothing happens. i had stall engine before too before cleaning that IACV.

so whats about that air flow mass sensor then ? i found as forester ppl talked about that this one can sause power loss and lagging with moving car.

and error says its kinda front O2 problem. but thats kinda not very much as O2 does .

or could it be both sensor like air flow and IACV ?

whats else then .

and more important is there any simple ways to test those parts for fault ? i heard to test catalyst you remove front O2 sensor and try drive as that. if power comes back then its catalyst fault. can it be true this test?

when i wanna car go quick and floor to metal car sometimes doesnt even move for like couple seconds. then when i want to overtake other cars i need to really floor it pedal full. and then it does something ... i thought it might just gearbox kinda slugish but then i read all those people have similar problems too.

thx all .
 
The symptoms you describe can be defective O2 sensors. It normally only happens when the engine is hot, after 10-20 km of driving.
 
so loss power , ohh and forgot to mention raised fuel usage too, those are not from air flow/ sensor ? or from IACV ? if car stall in midle of road from nowhere and then starts again and goes like its nothing . all this making one little front O2 ? you think so ?
i know my code says its P0420 but that can be caused by many problems still isnt it ? not just O2 itself
i think it can be cold engine too. its varies . sometimes its drives better and sometimes just worse. in mountains when i was in austria i was about 2200m above sea level and i was going up hills i felt like im driving fiat 500 classic model. just car felt like it doesnt have power at all. all cars where passing me. and i was flooring pedal all time. nothing more i could do there.
i just wanna be as much as i can sure about what i need to change because i no have money to change all those things.
 
Yes, loss of power and raised fuel usage can be caused by a bad O2 sensor - the car runs rich when the O2 sensor is bad.
 
so that would be first thing you would check ? couple local forester guys where telling that air flow could do those too.
any way to test it ? can i disconnect O2 and run or remove it and test some. or its no way to test it ? that P0420 sometimes stays off when i reset it , sometimes comes back faster.
and you talking about front O2 sensor yes ? i mean i have just 2 them. and rear one doesnt seams to impact on anything kinda.
and problem is not same all times. sometimes i t can run just fine. then next day it feels like crap for some time.
so its not clogged catalyst then ?
 
Yes, front O2 sensor. I'll see if I can find a test.
 
I'm 99% sure its the O2 sensor but don't blame me if I'm wrong !
 
i would want to believe you . because its not cheap sensor. what if i cnage just one front and left rear one old. they wont have problems then because they will be different makers or anything. ? what im finding is some Bosch o2 or Denso sensors here. and NGK ones. thats what i think are better quality ones at least.
some say if you change best to change both of them.
 
Pull your O2 sensor and buy a new one same make. But you shouldn't have any problems if its a different make or if you have an old and a new one. My Forester only has one O2 sensor though.
 
Thanks all but now more confusion for me. As i understood rear o2 sensor doesnt impact on engine in any wah just puts code . and code for me is not problem but just how car drives is. Worse thing if it catalyst itself and i will change o2 sensors and nothing will change. That would be bad mood for christmas.
Thing is i no getting any extra codes just that p0420 . if i would just fix that code and car would drive same badly its no point .
Same as those links i read lots more about it allready and on other places ppl where saying thats it can be even air flow sensor too.
Fuel presure regulator shouldnt be because its runs same on lpg too so its not just petrol or jusy lpg its same on both. So must be something with air mix or exaust
 
i guess its good thing to change O2 sensors as they need to be change after some time, at least Bosch says that every 160000 they need to be changed. so its good thing to do anyways. just not cheap one.
 
You can find cheap ones on ebay. Look for Blueprint, a Bilstein/Febi company but made in Japan !
 
well bosch and Denso ones are like about 90 for front O2 and about 30 for rear one. in other places they cost more yes. like 120 just for Bosch front O2 sensor. and we dont have those cheap ones. thats wierd because all other parts we have from blueprint or febi or else. but O2 sensors we dont have any cheaper ones here.
i saw cheap ones for forester 2.0 engines but not for 2.5 as i need . so i guess they no cheap for 2.5
 
Have you adjusted the idle control motor? Not sure if it is possible on the n/a engine, but have a look
 
does O2 sensors responsible for bad accelerations as i checked before and now my times on torque android app are :
0-30mph - 10 s
0-60mph - 17-19s
it can show HP too so it showed 124.1 hp on 2862rpm. but mostly if i check on that it shows about 70 hp.
i mean by internet even 1996 legacy outback did 0-60 in 9.7s. and i do 0-30mph in 10s ...
didint measured compression yet. that maybe one thing left that i didnt checked yet.
i mean im still not sure if thats only O2 sensors fault. could it be exaust ? catalyst? or no. just other day cleaned PCV valve and IACV they where not bad not so dirty and were not stuck.
like is there some method to what check in what order to get to problem ? i cant just change all sensors by guessing.
when i accelerate and i go pass 4k rpm sound of engine becoming kinda worrying. like valves metalic kinda click.

wait what .. ?
https://marksautocare.com.au/subaru-outback-abs-light-on
rear brake light bulbs can make your fuel messed up and loose power ? subaru what ? ... lol

I watched him fix it, by pressing the brake pedal, and while pressed, changing both of the rear brake light globes for different ones. He said he found the solution on some technical forum somewhere. It's like I've got a new car.
..?
i think tho my rear brake bulbs working

a tow bar can make you loose power ?
My Subaru Liberty wagon 2005 lost power dramatically, becoming an embarrassment up hill... this out of the blue (or as we thought), just after having installed the tow bar. Thinking it was the fuel filter, we changed that and there was no improvement. A few hours drive later, both the tail lights were gone. After reading your post, we concluded there was a connection between the tow bar and tail lights and loss of power. We changed the bulbs and disconnected the tow bar cables, and the car power was back to normal.
thats some next level stupid problem there.. haha
 
Unplug the O2 sensor and see what happens. It should run rich all the time meaning your engine will be thirsty.
 
Unplug the O2 sensor and see what happens. It should run rich all the time meaning your engine will be thirsty.

so whats changes would be then ? more power ? must run better ? i should feel it goes better ? and if its runs same then what? and if its runs differently then what ?
 
The O2 sensor sends signals to the ecu only when the engine is hot. Before that, the engine runs rich because there is no signal from the O2 sensor. If you unplug the O2 sensor, you will always run rich and you shouldn't feel differences but your engine will be thirsty. When unplugged, if nothing changes, you will know that its not the O2 sensor and if it feels different, it probably is a faulty O2 sensor...
 
The O2 sensor sends signals to the ecu only when the engine is hot. Before that, the engine runs rich because there is no signal from the O2 sensor. If you unplug the O2 sensor, you will always run rich and you shouldn't feel differences but your engine will be thirsty. When unplugged, if nothing changes, you will know that its not the O2 sensor and if it feels different, it probably is a faulty O2 sensor...

so best unplug on hot engine then yes? because on cold there is no point. ok ill try it then. i thought of that too.
 
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