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no low end power/acceleration


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Hi. I have a 99' legacy wagon (140k miles) that has developed an issue during the winter. I have no low end power despite holding the accelerator at a constant. It varies when the power kicks in, often around 3k rpms but sometime longer if starting from a stop going up hill. I took it in to my local subaru specialist (not the dealer). First they simply cleaned the master air meter and filter. This caused the issue to go away for a week and then came right back. Next I had a smooth roller replaced because the timing was slightly off. This took care of the issue for about 3 days and then came right back. What do I need to try next? Does this sound like a fuel/air mixture problem. I really don't think it's the transmission after the mechanics work. Let me know if you have any ideas, thanks. It has no other mechanical issues and has no loss of power on the high end, just no acceleration when starting from a stop.

 

Max

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  • 1 month later...
Have you received any info on thisissue? I have the same year, make, model and SAME PROBLEM!!! Started at end of winter. I was having some rough start problems and ran a gas type fuel injector cleaner which seemed to help the start problem. Then one morning on start up I heard a metallic "ping" and thought "that's not good!" Been having acceleration problems like yours since then. Any ideas would be appreciated.
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Does the car stumble or buck or backfire? If it's not doing that then it could be your transmission. Sometimes if there's a problem with some internal component (stuck solenoid/valve, worn bands or a bad clutch) some gears won't work right. You might get 1st gear good from a stop, but second gear won't work and it will go right to third which would cause a problem like you are describing. Do you have any problems with reverse? An air fuel mixture problem could be causing this but if there's no check engine light then it doesn't sound like this is the case. How's your gas mileage? Do you notice any strange smells? Your mechanic may have missed something. A clogged catalytic converter might cause this, but I haven't see it happen very often.
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You could have a sticky valve or a gummed up valve that is not closing all the way. I just did a rebuild where it has similar issues as yours and that was the problem. Do a compression check and try a product called seafoam, search and you will see how to use it properly, I use the PVC valve to pour the seafoam in.
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  • 1 year later...

I looked on many sites to find why i was bottoming out on hard excelaration in my subaru legacy 2.0ltr 1999 estate , many came away with exhuast and catylictic convertor failure also mass airflow sensor came into the forums aswell ...... owners of these cars should check the fuel filler pipe from where you put the fuel in to the rubber gasket where it connects to the petrol tank there is a plastic cover in the wheel arch which collects dirt and grime behind it this helps to corrode your fuel pipe thus breaking the seal to the tank causeing you to bottom out when hard excelarating due to lack of enough pressure to deliver fuel

I am no mechanic i found this out simply by accident when i noticed petrol leaking when i was filling up i now have it repaired and excelaration is back to normal

by the way shop around for a fuel filler pipe ie breakers yard as they dont come cheap lol

another ive left the plastic guard off and hammerite painted the new pipe

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  • 3 weeks later...

hi max, did you find a solution to this yet?

 

i have a subaru legacy 2004 stationwagon, manual.

 

my problem seems to be pretty much exactly the same. below 3000 rpm (mostly between 2000-3000), it pretty much has no power or acceleration. then it just kicks in. going up hills is terrible!

 

it happens in every gear, but only really notice it in first and second as by the time i change to third i wont usually go below 3000rpm. also is totally fine on the motorway - again might be because it is at or above 3000rpm.

 

also, it seems to be better after it has gone for a long drive (not just around town), and/or warmed up.

 

because of the lack of power i find i have to put my foot down quite a bit more and the fuel efficiency is really bad. i have a friend who used to own the same car who said his fuel efficiency was way better.

 

i took it to subaru and they said that it didnt give out any errors. my normal mechanic (who always does an awesome job & really trust worthy) said he couldn't say with certainty what it could be, but has a feeling it would be the air flow meter.

 

any help here with if you managed to solve it would be much appreciated!!

 

thanks

alex

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  • 2 years later...
Just posting here in the hope it might help someone else. My 2004 Subaru Outback auto would not go up hills. Foot to the floor, it would not rev over 3000. Always regularly serviced, my great mechanic couldn't figure it out - replaced fuel filter, still only two thirds fuel pressure coming through. Well, get this, it was something to do with the onboard computer that runs the engine (sorry for lack of technical details here) which apparently has some connection between the fuel circuit and the brake light circuit. 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. Good luck anyone who has this problem. It's a real pain. Sorry I can't give any more technical detail, but it might point someone in the right direction.
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That's amazing! Who would have known that? I never knew that a PCM (computer) could cause a fuel pump to act wonky. Computers can cause some strange issues though, sometimes disguising themselves as other problems. Had a friend with a mid 90's Oldsmobile Ninety Eight that backfired, sputtered, and lost power when it was floored. It wasn't a mechanical issue, but a problem with the computer (no check engine light back then) that made it think the car was going 100 mph and cut the fuel off. It was a simple fix, took a mechanic 5 minutes to reset something and it ran just fine after that. Go figure!
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  • 6 months later...

Just to clarify having seen that last post, in my case the brake lights were working fine. Mechanic changed them for a different type of globe (sorry don't know details of it). So if you've got the power problem, and your brake lights are working, it could still be this that's causing it.

Isn't the internet a wonderful thing!

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  • 3 months later...
Just wanted to thank you for your post. 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.
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  • 1 year later...

Not sure whether my problem is related but I've been putting up with my 05 standard legacy stuttering and stammering at low revs now for around two years. I've had my local mechanic look for faults and we've never been able to locate the problem. This morning I pulled and checked a few fuses for a seemingly unrelated problem - the window washer was not working. The washer is now working again just from pulling and reseating fuses (???). I also pulled a couple of other random fuses under the bonnet without the ignition on. After all this the stammering problem had disappeared!! The engine also wouldn't idle correctly and would cut out. My thinking is that in pulling the fuses I inadvertently reset the onboard computer which may have over time learned some bad engine management behaviors causing the low rev stammering. And by resetting the computer it's cleared it. I have since left the car idling and it has "relearned" its idle revs, and the low rev stammering problem is still fixed. Eureka! I hope it lasts.

 

Adding to what has been discussed above regarding the rear brake light replacement procedure, I wonder whether it's actually doing the same thing, i.e., resetting the onboard computer? And all that's required is for the computer to be reset?

 

Just chatted to my mechanic and the "standard procedure" for resetting the onboard computer is to pull the battery terminals off and touch the cables together. I'm not a tech or mechanic so do not do this unless it can be verified. [edit: according to a reply to this post in another thread be aware touching the battery cables could fry your electronics. Again, needs verification.]

Edited by mattwear
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  • 3 weeks later...

I had complete disbelief but understood it's plausible and possible so after replacing the fuel pump I was looking at the next round of parts @ $400 for injectors and a regulator.... Not happy and grasping at straws I read everything I could find on the interweb about a low power condition that seems like it is starving for fuel. I found this guys post and tried it out. I replaced both brake lamps and no-oxed the connectors then reset the ECU and cleaned the battery terminals while I waited. I fired up the car and let it idle while I had a smoke and then went for a spin. Damn if this thing did not hit like a sledgehammer and it seems like all is well. Only one drive cycle and not 50 miles yet but as of right now I could not be happier. I joined this forum just to say thanks for the assistance with the Subie community. This is my 5th subaru and the only turbo model I've owned. A fun drive but not a fun repair. Thanks all!! I'll post an update if anything changes after 50 miles!

 

Just posting here in the hope it might help someone else. My 2004 Subaru Outback auto would not go up hills. Foot to the floor, it would not rev over 3000. Always regularly serviced, my great mechanic couldn't figure it out - replaced fuel filter, still only two thirds fuel pressure coming through. Well, get this, it was something to do with the onboard computer that runs the engine (sorry for lack of technical details here) which apparently has some connection between the fuel circuit and the brake light circuit. 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. Good luck anyone who has this problem. It's a real pain. Sorry I can't give any more technical detail, but it might point someone in the right direction.
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  • 1 year later...
I am having the same issue! I have changed the fuel pump and filter. All the brake lights. Lol topped off the oil changed the spark plugs and I'm still have the issue. It's getting worse though. It's now happening through the entire rpm range. And my car is a total slug I have an cel code for fuel pressure and when it begins to flash when the car acts up. I need some help!
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  • 3 years later...

Hi

I am a new member of this forum and I hope to get a solution to my problem

My english is not excellent so please help me in simple language

My 2005 Subaru Legacy has a 2.0 engine

The car started very slowly, between 2000 and 3000 rpm

And very bad when hilly

When the battery cable is disconnected for a period of time, the problem will disappear and reappear after a short time

Did not give errors in the scanner

The specialist could not know the malfunction

He did everything necessary and we did not find a solution to this problem

Does the rear brake lights have anything to do with this malfunction or the exhaust muffler?

Please solve because I am tired of trying and spending money

thanxs

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If your brake lights are on all the time from a brake malfunction it would slow the vehicle at all RPMs and the brakes would get very hot. Not likely to be your problem.

 

If you have a clogged exhaust it would run better at low RPM and worse at high RPM because the engine would make more exhaust at high RPM and it would have more difficulty squeezing out of the clogged bit.

 

There is much more to solving car problems than computer codes. Many problems can exist without showing a code.

 

One clue you give is that the problem changes when you clear the computer of long term learned data by removing battery.

 

Two things come to mind that are worse at low RPM.

 

Vacuum leaks because the throttle closes off the intake so more vacuum forms and so more air goes in through the leak. This can be corrected by the computer to some extent with the long term learned data. This could also possibly tie in with a marginal oxygen sensor.

 

The other item that comes to mind that is worse at low RPM is if the timing belt has jumped some teeth so the cams and crank are out of time. It takes a very small amount of misalignment to give real troubles at low RPM.

 

Recipe: For the timing you can start by removing the outer timing covers and looking at the assembly marks to see if they are all correct at the cams. You would have to remove more to see the mark on the crank, but the normal thing is for only one cam to jump so you may be able to skip removing the center cover.

 

For the possibility of a vacuum leak the best way would be a smoke machine if your local service station has one. Vacuum leaks can be pretty hard to find on a Subaru as some of the leaks can happen under the intake where they are hard to examine or test. The smoke makes it easier to see them. For the oxygen sensor a scanner that can read live data is the way to go. That way you can look at the output of the sensor in real time while driving. This would require some close work with us on the forum to gather the correct data and compare it to normal. A shop should be able to do this.

Edited by doublechaz
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Thank you for this comment

My mechanic has checked the timing belt and it is well positioned

I had already switched the throttle air and it didn't help

I also replaced the coils, spark plugs, air filter, fuel pump and nebulizers

You mean a vacuum leak, where?

From the exhaust or from the engine body?

I measured the engine pressure and it was fine

And I cleaned the catalytic converter in the exhaust but didn't clean the muffler. Could the muffler clog up? This is a problem you think

And thank you very much for your reaction

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The muffler can become clogged although I don't see how. I had this happen. 7 psi exhaust pressure with muffler and near zero without it. You can unbolt the muffler from the pipe near the rear axle. If you can drive it this way without a police violation it will be easy to test. In my case I added another oxygen sensor location and added a pressure gauge in this port.

 

The vacuum leak would be in the intake and related parts somewhere between the throttle and the cylinder head. There are dozens of points here that could leak so inspection is a difficult path to take. Many small vacuum tubes come from the intake to sensors, emissions parts, etc.

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  • 1 month later...
I have just bought a 2008 Subaru Legacy 2.5i limited. I have changed spark plugs and wires, oil change with filter, air filter, took the throttle off and cleaned. When I am in park I can give it gas and the rpms will rev. I place it in drive and it’s a slow start to move and the ramps will go to almost 4 and I can’t go over 20mph. Also at times almost bucks. I don’t know what else to do Edited by Dsmale
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I would say the two most likely causes for problems that profound would be burned up and plugged catalytic converter, or jumped timing belt if the problem is with the engine. If the problem is with the auto trans, that's outside my experience.
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  • 1 year later...
On 7/7/2014 at 8:32 PM, treefern said:

Just posting here in the hope it might help someone else. My 2004 Subaru Outback auto would not go up hills. Foot to the floor, it would not rev over 3000. Always regularly serviced, my great mechanic couldn't figure it out - replaced fuel filter, still only two thirds fuel pressure coming through. Well, get this, it was something to do with the onboard computer that runs the engine (sorry for lack of technical details here) which apparently has some connection between the fuel circuit and the brake light circuit. 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. Good luck anyone who has this problem. It's a real pain. Sorry I can't give any more technical detail, but it might point someone in the right direction.

What do you mean by brake light globes?

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