zpratt2525 Posted August 23, 2016 Share Posted August 23, 2016 Hello all, First post here I have a 2007 Legacy, a four banging 2.5i, 5 speed sedan with 112,650(as of this post) miles Have now had the dreaded P0420 come up a couple times. Was told it was post-cat O2 sensor. Replaced it an went 3k and again, P0420. Was then told Pre-Cat O2 sensor. Went 3k and was told the pre cat wasn't screwed in all the way. Have gone another 500 miles and here we are. Little history, Bought the car used in October of last year and was lucky enough to have obtained all the prior records of it at the dealer from 97,000 miles until now. Head gaskets were replaced along with all other related gaskets, timing belt and drive belts. Exhaust studs were replaced on the head and it was machined. Everything was returned to normal. Used car inspection came back with nothing. Ran a freeze frame and here is a few numbers ECT: 86 degrees C O2 S B1 S2(V) 0.76 Run time of 592 sec EGR Command 51% EGR error 0 Engine RPM 2473 Engine speed 96 KM Intake manifold absolute pressure of 20.68 So... I'm not sure. My best guess is a Cat.... Watched a few videos and looked online, $329.00 with free shipping for OEM spec. I don't believe it be a exhaust leak since I crawled under the car and didn't hear/feel/see anything(soap bubble testing). There isn't any loss of power which I believe to a vacuum leak. Going to wait until the cat is cold so I can wack it so that I can see if anything is rattling about... Any help is greatly appreciated... meow Link to comment Share on other sites More sharing options...
Dead Mr. Posted August 23, 2016 Share Posted August 23, 2016 Maybe we should as the mods to just have one forum for ALLLL peoples threads. Do you know where you posted this? I mean unless you were looking for pics of cats and O2 sensors... Anyhoo if you want you can get a M18 spark plug fouler at any autoparts store. They can basically be used as an 02 spacer. You get 2 in a pack and you only use this on the rear sensor. They have a small hole drilled in them so only a small bit of the exhaust actually gets to the sensor and its killed any emissions code I have gotten resulting from removing the cats from my exhaust. If your sensor is long and doesn't thread on you can drill out the hole in the first fouler and then screw it into the 2nd to make it longer and then just screw it into the port of your exhaust. http://shop.advanceautoparts.com/p/dorman-help-spark-plug-non-foulers-18mm-tapered-seat-42002/5014964-p?iv_=__iv_p_1_a_214327102_g_12425515822_w_pla-191564128342_h_9008239_ii__d_c_v__n_g_x_pla_y_6201684_f_online_o_5014964-P_z_US_i_en_j_191564128342_s__vi__&utm_source=ACQ&utm_medium=cpc&utm_campaign=PLA&utm_content=shoppingcampaigns&gclid=Cj0KEQjw6O-9BRDjhYXH2bOb8Z4BEiQAWRduk1uHSx87pP5-CT5pEx6xRtkkEeQrIVflARiqbEUHyVQaAj-98P8HAQ Their are companies that make ones with stainless and bent pipes designed to do the same thing for WAY more money. Might be worth a try. Johann Build Thread to my 3.0R Build Thread to my Super Crazy MR2 Link to comment Share on other sites More sharing options...
Shipman Posted August 23, 2016 Share Posted August 23, 2016 Who cares where it was posted. Mods will move it. Link to comment Share on other sites More sharing options...
trevorno Posted October 7, 2016 Share Posted October 7, 2016 Maybe we should as the mods to just have one forum for ALLLL peoples threads. Do you know where you posted this? I mean unless you were looking for pics of cats and O2 sensors... Anyhoo if you want you can get a M18 spark plug fouler at any autoparts store. They can basically be used as an 02 spacer. You get 2 in a pack and you only use this on the rear sensor. They have a small hole drilled in them so only a small bit of the exhaust actually gets to the sensor and its killed any emissions code I have gotten resulting from removing the cats from my exhaust. If your sensor is long and doesn't thread on you can drill out the hole in the first fouler and then screw it into the 2nd to make it longer and then just screw it into the port of your exhaust. http://shop.advanceautoparts.com/p/dorman-help-spark-plug-non-foulers-18mm-tapered-seat-42002/5014964-p?iv_=__iv_p_1_a_214327102_g_12425515822_w_pla-191564128342_h_9008239_ii__d_c_v__n_g_x_pla_y_6201684_f_online_o_5014964-P_z_US_i_en_j_191564128342_s__vi__&utm_source=ACQ&utm_medium=cpc&utm_campaign=PLA&utm_content=shoppingcampaigns&gclid=Cj0KEQjw6O-9BRDjhYXH2bOb8Z4BEiQAWRduk1uHSx87pP5-CT5pEx6xRtkkEeQrIVflARiqbEUHyVQaAj-98P8HAQ Their are companies that make ones with stainless and bent pipes designed to do the same thing for WAY more money. Might be worth a try. Johann Besides ruining an already problematic cat, any downside to this fix? I'm concerned about damaging something more expensive. Link to comment Share on other sites More sharing options...
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