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Discussion Starter #1
OK......have done a lot of "feeling" around my exhaust system and cats and cannot find any leak. Also it sounds like a "pin hole muffler" sound under the hood. The car runs great with no check engine light. Been doing this for 4 weeks now. Can this be a failed rear cat starting to clog and pushing excessive pressure into the EGR? The putt putt noise alsmost sounds like its inside the intake. Thoughts guys?:huh:
 

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Can you tell if it happens at all rpm's?
 

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Discussion Starter #4
Yes, but at idle it sounds like the intake manifold is where the noise is coming from....that sucker is like a little speaker box.....so I am thinking is it via the EGR because my rear CAT is starting to clog and its pushing more exhaust pressure into the EGR:confused::eek::angry:? Again, the car seems to run fine overall and NO check-engine light!
 

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Do you do your own engine work? The best way to check for clogged cats is to remove the O2 sensor in the top and then use a boroscope camera to inspect down inside. If you don't have that available and you want to test your theory, you can separate the EGR valve from the bracket that mounts to the intake manifold. It is the joint that has the thin stainless steel restrictor plate/shim sticking out of it. You really only have to loosen the bolts enough that you are able to insert a 1 inch wide strip of thin cardboard,(like a cereal box is made of) down in between the shim and the EGR valve and then retighten the bolts. This will block off the flow and if it is what you think, you should hear a difference. ONLY DO THIS FOR AS LITTLE TIME AS POSSIBLE, BECAUSE IF YOU ARE CORRECT, YOU JUST BLOCKED OFF THE ONLY PRESSURE RELIEF YOU HAVE. If it was me I would just loosen the bolts up first with the engine running and see if there is pressure blowing out.
 

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Discussion Starter #6
Thats what I thought about the pipe from the rear cat....so if I take that connection off, the pressure flow should be very very weak....if its pushing then I have a bad CAT correct?
 

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Well the boys at work just found me a nice Olympus borescope.........what should I see when I still that baby down the rear CAT? Should I see a flat/consistent honeycomb? DO I need to look straight down or to the sides because the scope has the straight ahead lense on now. Let me know. CATS from Mazda are $1200/peice, Rockauto has then for about 400 or 550 dpending.
 

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Yes, if it is pushing then I would find someone with a boroscope and confirm that the cat is bad.
 

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Well the boys at work just found me a nice Olympus borescope.........what should I see when I still that baby down the rear CAT? Should I see a flat/consistent honeycomb? DO I need to look straight down or to the sides because the scope has the straight ahead lense on now. Let me know. CATS from Mazda are $1200/peice, Rockauto has then for about 400 or 550 dpending.
When you go in through the top O2 sensor port you should look straight down and see a smooth light grey ceramic honeycomb. I would still do the pressure test, because sometimes the blockage starts down inside the honeycomb and is not clearly visible.
 

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Tkemme......you are the best babe..........this scope is an older Olympus and does NOT have a integrated light source so I am hoping the O2 hole is big enough to put the scope down and then shine in a nice bright flash light......it has a separate light pipe but the dirty dogs at work can't find the F#$^'in light box!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Do I have to go in deep?
 

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No, only about 1-2 inches. If the thing wasn't stuck down behind the engine you would just use your eyes and a flashlight.

The car runs fine at all rpm's? No indication of any engine troubles????? Usually you start getting misfires/studders because of the high volume of hot exhaust gasses being returned and not flushed from the cylinders?
 

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Discussion Starter #13
Car runs fine..........but at idle it sounds like a pin hole in a muffler...then under the hood at idle you hear the blublbubblubblub and it sounds like its inside he intake!!
 

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You could have a bad intake valve :eek: leaking back. Do you have a manifold pressure/vacuum gage available?
 

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Discussion Starter #15
Got a vaccum gage.....where do I hook up and what should I look for....."pulsing" of the needle? Car idles/runs like a TOP thou and NO CEL lights.................
 

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Rapid pulsing of the needle in time with the sound. T into any one of the small vacuum lines just behind the throttle body.

Regarding CEL's.... your car can throw a rod, dump all its oil, catch on fire and burn to a smoldering heap and never throw a CEL if all the emissions components keep working.
 

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Discussion Starter #17
AMAZING!!! I will hopefully try these tests tomorrow and repost.....aslo seeing if I can borrow an extra car from my Brother until I figure this cluster out!!!! You ave been a great help...
 

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If they are clogged just get the MSDS header with a high flow cat. If you keep the stock cat back it is not much louder than stock and you get a real kick in the pants over 3000 rpm (I thought the car was fun before but now... I LOVE IT) for around the same cost to just replace the restrictive faulty stock pre cats... food for thought.
 

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Tkemme.....check vaccum tonight and its 21mg rock solid needle. The EGR restrictor plate.......do I loosen those 2 bolts that hold it to the mounting bracket, and then slide a thick piece of cardboard in-between? Looks easirer to do than taking off that exhaust feed pipe. When I did plugs at 80K that was a bitch at the time. Please confirm. Also at idle, there is very very very little flow out my 2 exhaust tips...normal?
 

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Tkemme.....check vaccum tonight and its 21mg rock solid needle. The EGR restrictor plate.......do I loosen those 2 bolts that hold it to the mounting bracket, and then slide a thick piece of cardboard in-between? Looks easirer to do than taking off that exhaust feed pipe. When I did plugs at 80K that was a bitch at the time. Please confirm. Also at idle, there is very very very little flow out my 2 exhaust tips...normal?
Yes, the two that hold the valve to the bracket. I am pointing to one in the first picture with the red stick. You just need a THIN piece of cardboard like I said in the earlier post. This may trip a CEL immediately, that you will have to clear after you remove the cardboard. Like I said earlier,you may just want to loosen the bolts a little first and then start the engine and see if you can tell a difference before you stick in the cardboard. The actual hole in the restrictor plate is quite small as you can see in the second picture. I included my spare EGR valve, bracket and intake tube in the picture just because I had them handy; don't get confused and think you have to take it all apart like that.

Your vacuum looks good and yes there is very little exhaust flow at idle. I'm still not convinced you don't just have an exhaust leak. Another thing you may want to try first is to start the engine in complete darkness and look for an exhaust leak using a small flash light with a well focused beam. DON'T DO THIS IN A CLOSED GARAGE! Any exhaust gas leaking out will be easy to see.
 

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