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Discussion Starter · #1 ·
Hey guys. Long time lurker needs a little bit of help.
Just recently my subi started losing power when driving uphill. Fuel pump change didn't do anything and after few weeks car started having issues all the time and gives no CEL. At this point It's pretty much undriveable. I can't get it past 80km/h. It acts fairly normal when idling but when the speed picks up it starts bogging and choking. In last few days I replaced spark plugs, wires, coil pack, air filter, cleaned MAF, cleaned throttle body, new cat. I tried testing AF sensor and it seems to be fine, however I am not an expert.
Yesterday, I was playing around with it in the shop and it would rev up normally to about 2500 RPM. Past 3K Rpms started going up and down roughly 200 rpms.
Any ideas what could be the problem?
Car has 240k kms, changed hg, timing and clutch 35k ago.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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almost like 'limp' mode????

could be knock sensor.

06 would be early drive by wire and the accelerator pedals have been a weak spot - usually get a code though....?


exhaust blockage can do this...vacuum gauge testing could show that.


live data may be helpful, if you have a smartphone, check into an ELM327 BT adapter and an app like Torque.
 

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Discussion Starter · #3 ·
It used be like a limp mode but now it seems like fuel/ air ratio is way off. When I was idling it at 3500 rpms after a minute or so coolant temperature started raising. Running lean?
Also, my fuel mileage went down in last 2 months by 3l/100 or even more.
I have never wanted a check engine light to pop up!
What would I look for when I hook it up to diagnostic tool?
 

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Some added info might be helpful . . .

Hey guys. Long time lurker needs a little bit of help.
Welcome. Where are you located? (North America, Asia, Europe?)

Just recently my subi started losing power when driving uphill. Fuel pump change didn't do anything . .
Was the complete assembly replaced, or just the pump motor?

. . and after few weeks car started having issues all the time and gives no CEL.
Does the CEL work? (Should be on when the ignition is set to ON, but engine not started.)

At this point It's pretty much undriveable. I can't get it past 80km/h.
Manual transmission; what gear and rpm?

In last few days I replaced spark plugs, wires, coil pack, air filter, cleaned MAF, cleaned throttle body, new cat.
Both cats, or just one?
 

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Discussion Starter · #5 ·
Thanks.
I'm in Canada.
The whole assembly was changed. I found a cheap low mileage used one.
Cel works. I unplugged the fron 02/ Af sensor to check if it would change anything and the light was on.
Only the front cat.
It's hard to tell what gear and rpm. I usually can't go into 5th as it's way too slow. Pedal to the metal and no difference. Wouldn't go over 3k rpms at all.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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06?

you might be able to have the car display troublecodes. there's a procedure for that.

even pending codes could help.

you mentioned overheating - it's imperative you moinitor coolant level IN THE RADIATOR, don't rely on the overflow bottle until issues with the car are resolved. various failure modes and old radiator caps, etc. can cause for confusion - make sure the radiator stays full.
 

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If you didn't test the rear cat converter, there's a chance it's restricted. One way to check is to monitor the MAF air flow data (g/rev) at wide-open-throttle. If a cat/exhaust is restricted the MAF will flatten out as the engine rpm goes up. (A vacuum gauge on the input manifold might reveal a blockage, but in a couple of cases here where the cat was partially blocked, the gauge didn't show this clearly.)

Another way to check the rear cat that has been used is to disconnect it from the front cat pipe. Noisy, but if the rpm will then go all the way to 5k or more with it off, that's the answer.

If you have a data scan tool handy, check the front A/F and rear O2 sensor data, along with the short and long-term fuel trims. If there's an air/fuel problem it should show.

If you don't have a scan tool, Romraider is a free program for Subarus that should work well with your 06 and provide a comprehensive list of parameters to monitor. The program is free, but runs on a Windows or Linux computer (laptop) and uses an inexpensive OBD-usb adapter cable (usually available from Amazon and eBay for less than $20). A similar program is FreeSSM, but it only displays data; it can't record it for subsequent sharing and analysis.

The built-in code reader that 1 Lucky Texan mentioned is described in http://www.subaruoutback.org/forums...9-how-read-diagnostic-trouble-codes-dtcs.html
 

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This is a slight thread bump, but I have a '06 with about 180,000 miles. Paperwork from the previous owner shows the front cat/manifold assembly was replaced (after the usual code was thrown) about 40K miles/5.5 years ago.

Over the course of a recent 180 mile trip back home in West Virginia terrain, it gradually lost power over the course of the trip - acting as if I was pulling a huge loaded trailer. It got so bad that It would not go much faster than 30 up some pretty gentle hills. It idles and runs smooth, and no codes, just no power.

I checked the important functions on Free SSM on my laptop - no apparent vacuum loss (i.e. manifold pressure increase) compared to the idle value at 2500 rpm in neutral. No misfires detected.

Based on the two previous threads regarding this exact problem, and the fact that the front cat was replaced not all that long ago I went ahead and bought a Walker rear-cat/pipe assembly. I took the old one off and, just to be sure, I started the car with the pipe removed. I braced myself for the loud sound of a wide-open exhaust manifold, the car started and then...silence. The wide open exhaust, was literally 95% as quiet as normal - even when revved and under load! Exhaust flow out the cat outlet had none of the force one would expect - the exhaust flow is weak and seemed to be only coming out of a portion of the pipe opening immediately downstream of the front cat (i.e. like water out of a half-full flowing pipe)

And, unsurprising, it is still driving like it is carrying 3 tons of bricks...

So, is it a pretty much an open and shut case that it is a clogged front cat? I'd like to get some opinion as the front manifold (really an exhaust header)/cat assembly is expensive - although this is a pretty good deal here compared to the OEM unit (over $800).

https://www.carid.com/2006-subaru-o...ytic-converters-466142498.html?parentsubmodel[]=ENGINE|2.5L

But no, I have not attempted to log a test drive to observe the MAF vs. RPM behavior yet.
 
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