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P0401 code - 99 Mustang six, auto

748 Views 1 Reply 1 Participant Last post by  appleimacdude
Had my engine rebuilt about 2 years ago at 180,000 miles, currently 222,000 - added bottle of ATS fuel system cleaner to about half tank of gas about a week ago - got check engine light few days ago, car still ran great. Yesterday, car developed a misfire, auto shops out here are booked for days or weeks, Went to OReilly to have code red - 0401 code. Tried looking up info on youtube, could not get round cap off the EGR vacuum regulator to check operation, it was mentioned to hold finger over opening inside this cap, car should run worse. Also mentioned to check for suction at EGR hose - ordered this part from Oreilly to arrive tomorrow morning, though I would see if the new part showed me how to remove this cap on the old part, to test - return part if necessary as new one would not have been installed yet. Thoughts on this? I read the EGR vacuum regulator is the most likely culprit, then the EGR valve -
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Update - tried again to replace the EGR valve on my 99 Mustang six, auto - it does not come off from the front as in the youtube video's, it comes off from behind a bracket, and I was trying to remove it again, removed the bolts that hold the EGR valve to the bracket in front, and was removing the bolts that hold the bracket to the solenoid or whatever to the left of it, to try to get enough room to remove the large nut that attaches the EGR valve to the manifold or whatever. I went to Oreilly to get an extension for my socket wrench to reach one of the smaller bolts holding it to the bracket = I was told this large nut on the side of the EGR valve requires a flare nut wrench, can't find out what size it is. On an old post, I saw it mentioned that the bolt could be 1", or 27 mm - any info on this? I didn't see anyone else mention using a flare nut wrench.
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