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Tips for replacing Catalytic Converter (Pre-Cat) BJ

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    Tips for replacing Catalytic Converter (Pre-Cat) BJ

    I am looking at replacing the pre-cat on my 2001 LX. This is something that I intend to replace myself in the home garage. My question to all is what tools are necessary for the job and what tips or tricks can you offer.
    It appears to bolt on/off easy enough but I am concerned about what i am not seeing. Any help would be appreciated.

    #2
    One option that you have is to replace the headers, pre-cat and j-pipe with aftermarket headers w/ non-fouler trick. I cannot give much more info than that as I have not done this myself. If you search this thread and mazdas247.com, then you should gain some more info. This may be cheaper and yield positive gains.

    Comment


      #3
      Pre-cat change.

      Originally posted by Proplayer View Post
      I am looking at replacing the pre-cat on my 2001 LX. This is something that I intend to replace myself in the home garage. My question to all is what tools are necessary for the job and what tips or tricks can you offer.
      It appears to bolt on/off easy enough but I am concerned about what i am not seeing. Any help would be appreciated.
      It's easy. I did it this past weekend. As long as you have some metric tools (Ratchet set and some combo wrenches) you should be fine. The only issue I had was that the bolt on the bottom of the pre-cat are studs and my replacement cat just simply had holes. So needless to say I had to make a run to the store for some nuts and bolts. And unless you are going to take off your exhaust manifold then you will have to take it out through the bottom. I also pulled off the plastic splash guard underneath. The only other part of my exhaust I had to mess with is the hanger bolt on the exhaust pipe that connects the Pre-cat to the exhaust (It gives you play to pull it out and put in the new one.

      Lastly, my new Pre-cat did not have the mounting holes to put the heat shield back on. But I didn't really care.

      Comment


        #4
        Thanks Guys for the info. I must say, I went ahead with the job and it wasn't that bad. Only took couple of hours at the most.
        highspdd you are right on. Unfortunately I didn't get you post till after I completed the job.

        Here is the process I took:
        1) Disconnect negative battery terminal.
        2) Remove intake on top of radiator.
        3) Remove top O2 sensor
        4) Remove manifold heat shield.
        5) Loosen the 5 nuts on top of Pre-cat(do not remove)
        Move to underside of car
        6) Remove splash guard
        7) Remove the bolts on exhaust pipe(spring loaded nuts) highspdd mentioned only removing the hanger bolt. I wanted more clearance so I disconnected the j pipe from the exhaust pipe. Removed bolt hanger bolt from J pipe.
        8) Remove lower bracket holding the Pre-cat.
        9) Break loose the nuts on the bottom of pre-cat.
        10) Removed bottom O2 sensor from the J pipe. Remove or unwind the wire from the heatshield.
        11) Remove all nuts from pre-cat, top and bottom.
        12) Everything drops out from bottom with the j pipe.
        Reinstall new Pre-cat in reverse.

        The kit that I purchased came with all the new bolts to install. I did have to purchase a gasket for the top of the pre-cat where it connects to manifold. My OEM metal gasket was broken. The new cat did not allow the cat heatshield to reinstall.
        So I moved the metal wire holder down to the j pipe heatshield and mounted it there.

        Hope this helps y'all get-r-done. Not really hard at all. Just do it!
        Done
        12

        Comment


          #5
          Thanks for this post, just changed out my pre-cat today and appreciated the guidance. The job itself wasnt hard at all. I had to make 2 trips to autozone to get bolts to attach to the j-pipe. I ended up using 10x1.25 30mm bolts, 40mm were too long. I called the local muffler shop and they quoted me $185 for labor to change it out. It makes me feel even better knowing what I saved!

          I would like to add to the above list to make sure you have new gaskets for the top and bottom of the pre-cat.

          As noted by other posters, I too had a coil pack go out and shortly after replacing got a CEL p0421. Inspection is coming due in March so I couldnt let this go. Thanks again!

          Comment


            #6
            Proplayer, highspdd and upanddown could you provide photos of your work and post them along with your installation steps. Also could you list brand and price of the aftermarket parts that you used. This would add to the utility of the thread and be very helpful for our Forum members needing to make similar replacements.

            Thank you.

            Happy Motoring!
            Last edited by goldstar; 02-17-2012, 08:59 AM.
            02 DX Millenium Red - The Penultimate Driving Machine
            MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
            MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
            Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
            MP3 Shifter, Knob and Aluminum Pedal Set
            Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
            Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
            Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
            Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
            Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
            Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
            Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
            Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

            Comment


              #7
              I dont have any pictures however the above steps are great, hopefully anyone reading this before they change out their pre-cat will have a camera with them.

              I went the way of Amazon.com for my parts, they have saved me tons of money on this project and on past jobs. I have never had a problem with their parts and shipping was free! Converter comes with 5yr 50,000mi warranty.

              Amazon.com (Autozone)
              Walker Exhaust 16220 Ultra Import Converter - $269.11 ($327.99 plus tax)
              Walker Exhaust 31642 Hardware-Gasket-DF - $6.18 (not available)
              Fel-Pro 61044 Gasket - $6.33 (not available)

              This fit my 2003 Protege 2.0 ES with no issues.

              Comment


                #8
                ^ Thanks for the additional information.
                Since I haven't done the job myself, I'll take your word for it that the posted installation steps are great and we'll make this thread a sticky.

                Happy Motoring!
                02 DX Millenium Red - The Penultimate Driving Machine
                MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                MP3 Shifter, Knob and Aluminum Pedal Set
                Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                Comment


                  #9
                  Sorry no pics of the job. I will try to accommodate the threads on future repairs.

                  As far as where I got the new part, I ordered it from Ebay from the notorious Canada seller. The part included all the upper and lower bolts. I needed to buy only a upper gasket for the part. The part is quite different in design buts it fits well. I don't have any ignition or timing issue so I didn't need any better part. If I get 36K from it I'm happy.
                  I spent about $120 shipped.

                  Problem Resolved
                  Done

                  Comment


                    #10
                    Thanks for the added details, Proplayer.

                    Happy Motoring!
                    02 DX Millenium Red - The Penultimate Driving Machine
                    MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                    MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                    Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                    MP3 Shifter, Knob and Aluminum Pedal Set
                    Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                    Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                    Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                    Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                    Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                    Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                    Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                    Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                    Comment


                      #11
                      had your engine light come on signalling a cat problem? does the cost include a cat and a pre cat or just one? I have a 99. I'm told it has 2 cat converters.

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