{"id":5655,"date":"2026-02-15T14:44:31","date_gmt":"2026-02-15T22:44:31","guid":{"rendered":"https:\/\/www.dognmonkey.com\/audi\/?p=5655"},"modified":"2026-02-15T14:44:31","modified_gmt":"2026-02-15T22:44:31","slug":"q7-3-6l-p0174-fixed","status":"publish","type":"post","link":"https:\/\/www.dognmonkey.com\/audi\/q7-3-6l-p0174-fixed.html","title":{"rendered":"Q7 3.6L P0174 Fixed"},"content":{"rendered":"<p><em>My Q7 is 18 year old and with 88k miles. This year my Q7 needs a smog certificate before it can be registered to drive in CA. It&#8217;s been sitting outside for a long time, I had P0174 Bank 2 Fuel Trim too lean popped up, also P0456 Evap has small leak. The gas mileage keeps going to 14MPG, even on the freeway. The car doesn&#8217;t run smooth and down\/up shift on transmission not smooth due to losing power.\u00a0<\/em><\/p>\n<p><em>After reading online, there are quite a few causes which one of them I don&#8217;t want to think of PCV valve under the intake manifold.<\/em><\/p>\n<ul>\n<li><em>Replacing the Air Filter didn&#8217;t help.<\/em><\/li>\n<li><em>Bought MAF cleaner to clean it and it didn&#8217;t help either.<\/em><\/li>\n<li><em>Bought a $12 gas cap on Amazon to replace the old cracking one and it fixed the P0456.<\/em><\/li>\n<li><em>Bought a $35 MAF on Amazon, replaced and it passed. The engine runs smoother, shift gear up\/down better, gas mileage better, more power.\u00a0<\/em><\/li>\n<\/ul>\n<p><em>The MAF part number 03H906461 and 0280218175 for 2008 Q7 3.6L.<\/em><\/p>\n<p><em>I&#8217;m very happy that I don&#8217;t have to replace the PCV\u00a0 under the intake manifold, it would be a lot of work.<\/em><\/p>\n<link href=\"\/idogjs\/icss\/font-awesome\/css\/ifotorama.css\" rel=\"stylesheet\"><script src=\"https:\/\/ajax.googleapis.com\/ajax\/libs\/jquery\/1.11.3\/jquery.min.js\"><\/script><script src=\"\/idogjs\/ijs\/ifotorama.js\"><\/script>\n<div class='fotorama--wp' data-ids='5669,5670,5671,5665,5673,5666,5668,5667,5672,5674,5675,5676'data-allowfullscreen='yes'data-link='file'data-itemtag='dl'data-icontag='dt'data-captiontag='dd'data-columns='0'data-size='large'data-width='276'data-auto='false'data-max-width='100%'data-ratio='0.46'><div id='gallery-1' class='gallery galleryid-5655 gallery-columns-0 gallery-size-thumbnail'><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon portrait'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0171.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0171.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0171-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"P0171 code\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon portrait'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0174.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0174.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0174-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"P0174 code\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon portrait'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0456.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0456.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_P0456-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"P0456 code\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_BOSCH_MAF.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_BOSCH_MAF.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_BOSCH_MAF-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Q7 Bosch_MAF\" srcset=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_BOSCH_MAF-200x112.jpg 200w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_BOSCH_MAF-300x168.jpg 300w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_BOSCH_MAF.jpg 600w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7-MAF.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7-MAF.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7-MAF-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Amazon Q7 MAF\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_IMG_1754.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_IMG_1754.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_IMG_1754-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Q7 Gas Cap\" srcset=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_IMG_1754-200x112.jpg 200w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_IMG_1754-300x168.jpg 300w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_IMG_1754.jpg 600w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_old_gas_cap.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_old_gas_cap.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_old_gas_cap-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Q7 old gas gap\" srcset=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_old_gas_cap-200x112.jpg 200w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_old_gas_cap-300x168.jpg 300w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_old_gas_cap.jpg 600w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_MAF_cleaner.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_MAF_cleaner.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_MAF_cleaner-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"MAF cleaner\" srcset=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_MAF_cleaner-200x112.jpg 200w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_MAF_cleaner-300x168.jpg 300w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_MAF_cleaner.jpg 600w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7-Gas-Cap.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7-Gas-Cap.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7-Gas-Cap-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Amazon Q7 gas cap\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7_air_cleaner.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7_air_cleaner.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7_air_cleaner-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Q7 air filter\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7_Air_Filter.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7_Air_Filter.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_Q7_Air_Filter-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Amazon Q7 Air Filter\" \/><\/a>\n\t\t\t<\/dt><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_q7_air_replace.jpg' data-full='https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_q7_air_replace.jpg'><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"112\" src=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_q7_air_replace-200x112.jpg\" class=\"w3-image attachment-thumbnail size-thumbnail\" alt=\"Amazon Q7 air filter\" srcset=\"https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_q7_air_replace-200x112.jpg 200w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_q7_air_replace-300x168.jpg 300w, https:\/\/www.dognmonkey.com\/audi\/wp-content\/uploads\/z_q7_air_replace.jpg 600w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/a>\n\t\t\t<\/dt><\/dl>\n\t\t<\/div>\n<\/div>\n<ul class=\"lcp_catlist\" id=\"lcp_instance_0\"><\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>My Q7 is 18 year old and with 88k miles. This year my Q7 needs a smog certificate before it can be registered to drive in CA. It&#8217;s been sitting outside for a long time, I had P0174 Bank 2 Fuel Trim too lean popped up, also P0456 Evap has small leak. The gas mileage <a href=\"https:\/\/www.dognmonkey.com\/audi\/q7-3-6l-p0174-fixed.html\" class=\"more-link\">&#8230;<\/a><\/p>\n","protected":false},"author":2,"featured_media":5670,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[39],"tags":[1239,1240,409,1234,798,801,1238,144,1235,1233,420,1232,1231,1237,1236],"class_list":["post-5655","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-q7","tag-1239","tag-03h906461","tag-air-filter","tag-bank-2","tag-cel","tag-emission","tag-evap-leak","tag-fail-smog-check","tag-fuel-trim-lean","tag-gas-cap","tag-maf","tag-p0171","tag-p0174","tag-p0456","tag-system-too-lean"],"views":37,"_links":{"self":[{"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/posts\/5655","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/comments?post=5655"}],"version-history":[{"count":3,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/posts\/5655\/revisions"}],"predecessor-version":[{"id":5677,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/posts\/5655\/revisions\/5677"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/media\/5670"}],"wp:attachment":[{"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/media?parent=5655"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/categories?post=5655"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.dognmonkey.com\/audi\/wp-json\/wp\/v2\/tags?post=5655"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}