JohnCTT
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Posts posted by JohnCTT
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I had one in my daughter in law's 09 2.5 at less than 100K miles.
But, that car head a dead number four. It was literally running on three cylinders.
John
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12 hours ago, Mike104 said:
I believe the later vehicles use the rear O2 sensor for fuel trim so the spacer can set other codes. There is a great P0420 code thread over at Outback forum
https://www.subaruoutback.org/threads/p0420-diagnosis.49537/#post-474237
It's long but the first few pages have the good info. May not be a cat but if it is OEM is the way to go. Others don't last as long. Some have P0420 code return in a few months. Main issue is to figure out why the code is set before replacing the cat.
Thanks Mike, I'll go through the list.
This car though had a blown piston and bad skip, so it seems clear the cats were stuffed with raw fuel from the dead bore. My daughter in law was out of town and drove it with the broken piston until it quit. In addition, the second cat was replaced right after I rebuilt the engine because it was plugged with debris from what I assume is the manifold cat innards, so I'm pretty sure a fair percentage of the manifold cat substrate broke up.
Still, going over that list, I still can't see why an exhaust or intake leak or injector issue would set a cat efficiency code but not a lean/rich condition. Stranger things happen I suppose.
John
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Hey guys, I installed a brand new Subaru short block in my daughter in law's 2009 Legacy 2.5 non-turbo about 6 months ago because it had a broken piston:
It's running normally (thank God) but keeps setting a P0420 cat efficiency code, so I need to replace this. I already have over 5K in this car and would like to minimize the cost of replacing the cat if it's reasonable to do so. So I have two questions: are the aftermarket cats safe bets to work properly for a few years without setting codes or is the OEM cat/manifold the only safe option? If the OEM is the only way to go, is there an on-line site that has discounted prices?
Near as I can tell, the OEM is going to cost me $900 but there are aftermarket solutions for less than a fourth of that.
Thanks for any insight.
John
EDIT: On other cars, I've used O2 spacers to eliminate the efficiency code , but the downstream O2 sensor seems to be in the *middle* of the cat on this Subaru. Am I seeing that correctly? Can a spacer be used successfully on these cars?
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On 6/28/2019 at 9:35 PM, GeneralDisorder said:
The Long term at -8.... but what was the short term?
GD
I'll have my son check the short term trim when it's fully warm. Should that be taken at a specific rpm in neutral, or should it be under load?
BTW, I just checked my Mazda with my scanner, and the STFT changes constantly, although my cheap scanner updates once every 5 seconds. There are no codes stored and no CEL on. Thanks for the help.
John
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12 hours ago, GeneralDisorder said:
And for the love of god please would you people stop honing cylinders?!? Damn when will this wives tale die already?
GD
Do you mean don't hone at all (leave as is) or do a full cut?
Anyway, I didn't completely understand the AF description, but I had my son check the fuel trim with his scanner, and he said it had a Long Term Fuel Trim 1 of -7.7% and a Long Term Fuel Trim 3 of -100%. Since this has a single cat after the collector, this is a one bank system even thought it's a boxer, correct? I assume the Trim 3 is meaningless.
Does this lean towards a bad cat?
Also, you used the term AFR sensor. Does the Subaru use a full range sensor or a standard binary O2 sensor?
John
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13 hours ago, nvu said:
There's a gasket 3" away from the rear o2 sensor. 44184. It doesn't look like the older donut style that tends to leak though.
I tried https://www.google.com/search?q=subaru+2009+legacy+p0420, only thing that sounds plausible is cleaning the maf.
Maybe I'm looking at this wrong, but it seems the upstream O2 is in the collector before the cat, but the "downstream" O2 is actually in the **middle** of the cat. {???}
John
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2 hours ago, 1 Lucky Texan said:
....on older cars, that sensor is just a cat conv 'nanny' and could be ignored or 'cheated' with a spacer or a coupla resistors to clear the code, but on most(?) newer cars
( and, it seems, on Gen2 H6es), it seems to also be used by the ECU to modify a:f .
Forgive my Subaru illiteracy... is the 09 2.5 Legacy one of the newer ones that use the downstream O2 for AF ratio?
John
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3 hours ago, nvu said:
no lean code means the front o2 sensor is happy with the air coming out the engine. p420 is when that air goes through the cat and hits the rear o2 sensor. the engine is fine, the ecu is not happy with the air coming out the cat. exhaust gaskets, bad o2, bad cat. nothing to do with intakes
That's what my intuition tells me, but if you Google P0420 codes, every return will mention intake leaks! Doesn't make sense to me either.
Anyway, the Subie exhaust is a one piece all welded affair, is it not? I'm guessing a bad cat, but the exhaust gaskets from the heads on out can only cause a lean code, not an efficiency code?
Thanks for help guys.
John
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On 4/8/2019 at 10:01 PM, Mike104 said:
General consensus on aftermarket cats is they are junk. You will probably get a P0420 code shortly after installing them but YMMV
Well, I got a P0420, but I'm still using the original cats.
Here's what I don't get; in researching P0420 codes, many people talk about intake leaks and such. In my experience, and air leak will cause a lean code. I don't understand how an air leak can cause a normal response for the first O2, but cause an efficiency code. Am I missing something here?
Because the car had a misfire from the blown piston, I'm assuming the cat on that bank was damaged and that's what's causing the P0420 efficiency code. I don't mind replacing the exhaust manifold/cats but don't want to if that's not the problem.
BTW, I had to reregister because every time I try to log in, it always says wrong password and locks me out. So then I have to wait for the time out, and then go through the process of changing passwords. Unfortunately, it hasn't taken the same password twice.. Hopefully my new account will work.
Thanks.
John
Fuel trim -7.7% Normal? (P0420)
in 1990 to Present Legacy, Impreza, Outback, Forester, Baja, WRX&WrxSTI, SVX
Posted
I'm getting a P0420 on a 2009 Legacy 2.5L (no turbo). This came after an engine rebuild required after a ringland failure of #4. Also, after the engine rebuild, the lower cat was found to be plugged with what I assume are parts of the manifold cat, so I suspect the manifold cat was damaged when the car was run with the dead cylinder sending unburned fuel to the cat. Changing the lower/back cat restored power and the car runs fine except for the P0420 code.
Scouring this forum, I found many references to checking fuel trims before condemning a cat for a P0420. According to a cheapo scanner, the long term fuel trim is -7.7%. Is this within range for normal fuel trim?
Thanks for any input.
John