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2008 Legacy Engine struggling

2.9K views 5 replies 3 participants last post by  GigaMike  
#1 ·
Sorry, this is a duplicate post with one in the year specific section. I am desparate.


I know this is an outback forum, but the 2008 legacy is similar. Desperate for help.

My son's 2008 Legacy 4AT 2.5i died on the side of the road. I towed it home and heres the story:

You can start it, it idles, but when you give it any gas it either bogs down or allows the rpms to get to 3000 but constantly dips down to 2.5 or less until it eventually just stops revving at all and practically stalls. The exhaust is very strong during all of this.

He had codes for a little while p0420 and p0457 which indicate a catalytic converter issue so I thought maybe the cat finally got clogged and when I towed it home, i ordered a new Cat. I replaced that along with brand new Denso O2 sensors and that didnt help one bit.

When the car died it was also throwing p0731 which has something to do with not getting into first gear. I thought this was a symptom and not a problem but a friend thinks the car could be stuck in LIMP MODE??? I currently have no other codes on the car. I have pulled the battery for 12+ hours, etc... You can start the car, move into reverse, or even 1st and 2nd gear when in sport. the car travels but you cannot rev one bit or it will die.

When this first happened, he said he had to accelerate really hard to get from a red light. He said he put it in sport, and was in first gear, and when he shifted to second gear, is when the engine started to bog down and he pulled over. So maybe the p0731 is related, but I dont know what to do about it.

Im not sure what else to check because there are no codes. I cant tell if this is truly a transmission issue, and its in limp mode, or if there is something else going on with the intake / exhaust.

I downloaded romraider last night and ran it for 15-30 seconds while I reproduced the bogging down issue. Im attaching the romraider logs here because I have no idea what to even look for. The file was renamed to .csv.txt fyi.

One last thing, the transmission fluid is full (if anything too full) and is showing some browning. I was planning on replacing the fluid today.

Thanks in advance
 

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#2 ·
Check the fuel filter in the fuel pump assembly that is in the fuel tank.

The fuel filter cover cracks and allows the fuel to escape causing low fuel pressure/volume to the engine. This is a common problem and may be the cause of your problem.

Seagrass
 
#4 ·
Thank you both.

It idles perfectly for what its worth and Im not seeing any misfires. I will check the belt though. It was replaced about 20k-30k miles ago.

Regarding the fuel filter. It looks like a lot of work... Would a fuel pressure gauge help troubleshoot before taking this whole thing apart?

Thanks.
 
#5 · (Edited)
I put a fuel pressure test gauge on the fuel lines near the engine. The SUPPLY line is reading 50-55PSI.

The RETURN line is reading ZERO. I even unhooked the hose and there is no gas going back to the tank. Is this perhaps my issue? If so, how do I fix it? What is the issue?


Scratch that. Turns out this car doesnt have a return line, that is an EVAP line I guess.

So to recap, when you first start the car, it runs great for about 20 seconds. You can rev as high as you want and everything. Then it starts to bog down upon pressing the gas pedal. I am at a loss here.
 
#6 ·
Update...On a hunch I disconnected the exhaust at front cat so just the new front cat is on... Started the car and it revs just fine. no more bogging down. So I must have a clog in the rest of the exhaust system. The honeycomb in the old cat is partially missing so I am wondering if a piece of it came off and clogged the exhaust further downstream. I will spend some time tomorrow taking off various pieces. Maybe its the rear cat that needs to be replace now too...