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Discussion Starter · #1 ·
Hey Guys-

New to the forums, but thought that this may be the best place to ask for opinions. I recently purchased an 05 outback with 132k on the OD. The day we took it off the lot of "subarus and more" in the upstate of South Carolina the check engine light came on. We had it checked and it popped up with saying Cat. Converter (I want to say 420 code??) was going bad. The dealer assured us that was normal and that it should be ok. A week or two later the outback starting hesitating/fuel deliver issue type thing (a stutter?) while we were driving. The next day it was so bad we couldn't drive it a mile and the check engine light was blinking. Took it back again and a spark plug was bad... so they replaced all four. (oh yeah, it's a 2.5 4 liter) after a days the check engine light came back on. A few weeks later the jumping/stuttering began again, along with a low idle. now it continues to jump/stutter/low idle... I'm pretty tired of this as we just paid close to 10k for a "new" car and got rid of a kia rio because it was doing the exact same thing. Does anyone have ANY suggestions or clues as to what may be happening? Any and all advice is greatly appreciated.

Zach

ps- my first car was an 87 subaru station wagon gl... I've heard they've gotten better since then.
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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Sure. This car may be new to you but it is at its point in life where it is going to need things. the 420 code is the front o2 sensor(s). They do wear out with time, and this is an acceptable mileage to do this. this is the nose of the emissions system, and with it not functionining it can cause exactly what you are seeing.

you should also consider getting a full tuneup, wires, filters, pcv valve.
 

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Search the forum for 0420 code and read! Could be any number of things causing this and it needs to be addressed not just let go.
 

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Discussion Starter · #4 ·
Thanks for the feedback guys. I say new because the seller buys these from auction and is supposed to fix everything before he sells them. I understand that cars have normal wear and things need to be replaced. Also- I'm familiar with searching forums but wasn't even sure what to search for at all. Thanks again. I'll probably take it to my local mechanic to replace the o2 censor and see what it does from there.
 

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Fresh Out of Outbacks!
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Insist on an OEM sensor. The car should have 2 sensors, one before the cats and one after. The first measures how much total junk is in the exhaust, the second measures how much was converted by the cat, and the computer manipulates the engine based on signals from both.

Experience has shown that you can get away with the cheap "generic" replacement sensors for the rear, but you're just buying more trouble if you use anything but the real deal for the front.

I believe Denso was the OEM supplier for '05.

It is possible to do a methodical diagnosis to determine in advance exactly which part is bad before you go swapping stuff, but sometimes you can roll the dice, swap the front sensor and come up roses. Cardoc's P0420 diagnosis thread has all the details.

Good luck!
 

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For the P0420, read http://www.subaruoutback.org/forums...ce/49537-p0420-diag.html?highlight=P0420+diag

Also, if the CEL is on, but the engine is "jumping/stuttering . . along with a low idle" there could be another code (or codes) that should be identified and dealt with. (The symptoms are similar to those when misfires are happening, and that could be due to fuel delivery, bad wires, or a defective coil.)

As in the linked thread, sometimes there's a need to do some proper analysis in order to narrow down the actual cause, before changing parts.
 

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2005 Outback 2.5 SE (UK spec)
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If it helps I bought a subaru 2005 legacy estate 2.5L SE few years back. Drove it from the private dealer in the UK and the check engine warning light came on too. Basically after a crap dealer experience (hiding the error codes by reseting warning lights over 3 months) and refusal to fix it ... It turned out to be the 1st cat of the 2 cats which are in series on the 2.5l had failed eating lambda sensors. Sadly as its one whole section combining two separate cats the whole section had to be replaced and the corresponding lambda sensors to be safe. All was solved by doing this... At a cost sadly to my own wallet via my trusted local garage in my village. The cats on the 2.5l engines appear to be very costly indeed. Ended up cheaper to have one custom made by performance exhaust specialist in the UK.

The symptoms you describe are identical to what I experienced. Hence me posting to see if it helps.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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+1 What Plain OM said. Check, check and check again. Don't throw parts at it.

Check the fuel filter and coil, air filter and pcv valve. Check the battery and alternator output.

If there are any codes additional to the P0420, post them.
 

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Discussion Starter · #9 ·
I'm not sure where I could get a proper analysis - as it seems my local mechanics tend to be extremely inept. Including the owner of the dealership where he specializes in subarus.

I was hoping to see if I could replace the o2 censors myself in the next day or two to see if that would help or fix it. My brother has been suggesting to me to straight pipe it as we don't have emissions tests here in South Carolina... any thoughts on that if the o2s don't fix it?

As far as the code readings, both the mechanics I've taken it too only read the 420 code and said that it was not reading any other codes. The CEL comes on and off (along with the cruise control light, it blinks) as a matter of fact driving it earlier the CEL went off, and hasn't popped back on yet... I know it will as it still has the low idle issues and the stutter/jump. Obviously I'd like to fix this and I have no plans of letting it go without proper maintenance. Thanks again guys, I know it's pain to hear or see the same issues come up, but this issue is new to me so thanks for understanding.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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Did you read through here: http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diag.html

A Catalyst Efficiency code most times, 98% of the time, means there is an issue with the engine performance. Straight piping it will increase the outflow of the engine exhaust, but the code will be there, and whatever problem created it will also. And, if the MIL is illuminated all the time, you won't know if something else pops up.

Emission testing state or not, the engine is not performing the way its designed and you should find out why. Not try to cover it up.
 

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Discussion Starter · #11 ·
Thanks for the info, I will be reading through the thread you and others have mentioned. I haven't had the time yet, but I will make time tonight. Thanks
 

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Discussion Starter · #12 ·
So I just heard from the mechanic who was supposed to run a diagnostic on the subaru and he just stated that the cat converters aren't performing up to par and that it'll be $500 to replace both. Is this a good deal? Should I take it to a third mechanic to "diagnose" it?

edit - a fourth mechanic
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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$500 for 2 cats is a good price. Chances are, given the price he quoted, he probably checked them and isn't out to empty your wallet.

You can ask him how he determined the cats were bad. If he truly knows he will be able to explain it and show it to you. Refer to the video and graphs I posted in the "P0420" thread.
 

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'05 2.5i H4 4-Speed Auto w/Sportshift
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Our '05 Cat-Converter(s) went just before the warranty was up. A Subaru dealer in Montpelier was very thorough in replacing it/them along with two sensors (I think), while my wife waited about 3 hours.

Same issues, wouldn't idle, no power, real low idle almost stalling, etc.

After she drove it home, I noticed the idle was back up above about 700 or so where it had been below 500 or below 400. When it idled, the whole car shook, just like the thing was about to stall.
 

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Discussion Starter · #15 ·
Thanks for the advice and help guys. Just got the subaru back on friday. My wife drove it for about an hour with no issues at all, then I drove it to the couple of stores and it began to do the same thing. Now it's worse though, I'll probably have to have it towed back to the mechanic this time.

I thought it may be the spark plugs because they had already fouled up once before, so I just replaced them with Denso's PK20TT 4504 "platinum" spark plugs. Didn't fix anything.

I asked the mechanic if he did the Diagnostic (which is why I took it to him in the first place) he says he did, he says the sensors both front and back were ok...

I'm thinking now to just replace the o2 sensors myself? Unless there's a way that I can do a thorough diagnosis myself on the car. Anyone else have any suggestions?

The symtoms are just as Saint J VT stated, low idle and the whole car shakes as if it's about to stall. It's gotten worse since I've gotten the two new Cat. Converters in it.
 

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I am bowing out of this as the cats were replaced, and I honestly dont think that they were the issue.O2 sensors should have been replaced first, not last. You may have just replaced tow perfectly good cats with two inferior ones. Good luck.
 

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Not to mention the classic Ma and PA muffler shops can cut out and replace CAT's for 1/3 the price that Subaru charges for the bolt on part.
 

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Discussion Starter · #18 ·
I am bowing out of this as the cats were replaced, and I honestly dont think that they were the issue.O2 sensors should have been replaced first, not last. You may have just replaced tow perfectly good cats with two inferior ones. Good luck.
Yeah, I took it to three different mechanics asking for a diagnosis, finally thinking this one was going to do one similar to Cardoc's thread with the very thorough checking of everything. Oh well I guess it's all I can do with the inept mechanics around here.
 
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