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Discussion Starter · #1 · (Edited)
car is a 98 5spd.

blew my 2.5, swapped in a 96 2.2 w/ 160k. have been driving on this motor for just over 6k miles. been getting p0420 code a few times monthly since i've owned the car (16k miles).. never smelled the cats.

car idles low at all temps, and stumbles/misses a bit. no cels. slight hesitation at slight throttle around 2k if i am lugging it a bit. (has done this since the swap, the idle issue is new)

i now average 22mpg (which is also my best), which seems low to me, considering i averaged 26 with the 2.5, with a best of 29. is this just due to the power decrease, or related to the idle/hesitation?

new parts:
air filter
fuel filter
pcv valve
front o2 sensor
plugs (properly gapped, proper ngks)
plug wires (not oem, never had issues in the past using aftermarket wires, but read others have had issues)
new tbelt, etc. (rechecked timing!)
checked many times for vac leaks.
seafoamed through brake booster line (first time trying it, never been a believer in this stuff, still am not)
swapped knock sensor from 2.5 (changed plug)
swapped cam/crank sensors from my 2.5

i had been getting all 4 cylinder misfire codes at 5000 miles into the swap, which started immediately after the fuel filter change, and went away after redoing the timing/swapping cam/crank sensors. the car drove fine and did not miss, and the idle problem did not go away when the codes stopped coming.

today i will be cleaning the IACV/TB, and MAF. i just wanted to see what ideas people had. i have searched extensively, but only found one thread specific to these issues on a swap.
 

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01 Outback H6 VDC, 97 GT wgn w/ ej22, 98 OBW w/ej22
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the p0420 is a o2 sensor issue. was the replacement o2 a subaru item or aftermarket?

you can eliminate the trouble code with an extension on the rear o2 sensor. but if the front one is not working well you could still have issues. it controls the fuel air ratio.

if the idle problem started after the timing belt, then i would review everything you did then. look for a loose vac line or wire. especially the lager hose directly under the black plastic intake that connects to the IAC.

no trouble codes other than the p0420?
 

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Discussion Starter · #3 ·
the p0420 is a o2 sensor issue. was the replacement o2 a subaru item or aftermarket?

you can eliminate the trouble code with an extension on the rear o2 sensor. but if the front one is not working well you could still have issues. it controls the fuel air ratio.

if the idle problem started after the timing belt, then i would review everything you did then. look for a loose vac line or wire. especially the lager hose directly under the black plastic intake that connects to the IAC.

no trouble codes other than the p0420?
the o2 sensors are operating within the proper voltage range, and appear to operate as they should (i have a bluetooth obd2 scan tool and torque app on my phone, so i've monitored them while driving), the new front o2 sensor is NTK brand, which i haven't had any issues with on my last 2 subarus. i plan to space the rear sensor, someday.. clearing the code every now and then hasn't bothered me enough yet. there are no other constant or recurring codes.

the idle problem started over 5k miles after the motor swap/t-belt change, at the same time the "misfire" issue occurred. redoing the timing (it MAY have been off a tooth on the left cam), and cam/crank sensor swap eliminated the misfire codes, but not the rough idle. i said the idle problem started after redoing the timing, but that's not true, it just became THE problem. it started after the misfire codes became almost constant, and i started feeling a small skip under load, once or twice per trip. things got worse, but then disappeared after the timing and crank/cam sensors. except the idle.

i just had the intake apart again last night, and there are no missing/disconnected/cracked hoses. i read something about intake manifold gaskets deteriorating on older motors, so i'm going to look at those more closely, along with cleaning the iacv, tb and maf.

this motor sat in a tire on a garage floor for a few years before i picked it up for $20, so i'm trying not to get too flustered about chasing down this problem!
 

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01 Outback LL Bean
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I have worked on many 92 EJ22's and never seen an issue with the intake manifold gaskets deteriorating. If you think you have a vacuum leak then spray around the engine with carb cleaner or similar to check for leaks.

There is a ground wire that attaches to the drivers side/top/rear of the intake manifold. If this comes loose it will cause all sorts of drive ability issues. Check to make sure its tight. It is the primary ground wire for the ECU sensors.

NTK O2 sensors are made by NGK. They are good quality.

A P0420 does not indicate a faulty 02 sensor. It says that the readings from the secondary 02 sensor which sit behind the CAT are indicating that the CAT efficiency is not good. This code can be tripped due to a failing CAT, a faulty secondary 02 sensor or a very poorly running engine.

Have you checked the plugs?

I would consider doing a leak down or compression test if all else fails.
 
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