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Discussion Starter #1
Hello. I have a 2001 wrangler with the four cylinder, everything is pretty much stock. I was driving the other day and out of no where I encountered a noise that sounded like an exhaust leak. I pulled over and narrowed it down to a factory hole in the exhaust manifold. It is at the bottom of the manifold just before it connects to the pipe leading to the muffler, but on the manifold side. The hole is threaded. It looks like a sensor could go there, but there is no evidence of any wires dangling or anything being disconnected. I went to a few auto part stores but that proved to be worthless. Does anyone know why this hole is there and should it just be plugged with a bolt? If it can/should be plugged, does anyone know what size?
Thanks!
 

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Hello. I have a 2001 wrangler with the four cylinder, everything is pretty much stock. I was driving the other day and out of no where I encountered a noise that sounded like an exhaust leak. I pulled over and narrowed it down to a factory hole in the exhaust manifold. It is at the bottom of the manifold just before it connects to the pipe leading to the muffler, but on the manifold side. The hole is threaded. It looks like a sensor could go there, but there is no evidence of any wires dangling or anything being disconnected. I went to a few auto part stores but that proved to be worthless. Does anyone know why this hole is there and should it just be plugged with a bolt? If it can/should be plugged, does anyone know what size?
Thanks!
You have a replacement exhaust manifold that was built to use on YJ's and TJ's and it has the O2 sensor outlet for the YJ that is plugged for the TJ, so I suspect the plug probably cooked to a crisp and fell out. A lot of 2.5 owners have had similar issues including me.
 

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@TJ4Jim , thanks for the info. This makes sense and explains why I couldn't find it on diagrams for my jeep year. I don't suppose you know what bolt size needs to plug the hole? It's a wide hole and lowes doesn't carry a bolt this large with fine threads.
 

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@TJ4Jim , thanks for the info. This makes sense and explains why I couldn't find it on diagrams for my jeep year. I don't suppose you know what bolt size needs to plug the hole? It's a wide hole and lowes doesn't carry a bolt this large with fine threads.
As long as it's a standard O2 tap the thread should be M-18 x 1.25 like this.

 

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Discussion Starter #6
@TJ4Jim , Great! Thank you so much! You've saved me money in buying a new O2 sensor to plug the the hole or going to a hardware store and buying a handful of bolts to find the right size.
 

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@TJ4Jim , Great! Thank you so much! You've saved me money in buying a new O2 sensor to plug the the hole or going to a hardware store and buying a handful of bolts to find the right size.
Try a NAPA or another established parts store for that plug.
 

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There is a small metal plate and two bolts covering that hole. See if Rock Auto has picks on replacement manifold for better view
 

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Discussion Starter #9
TJ4Jim got me all set up. I was able to go to my local nut and screw place and get a plug that fit perfectly.
 
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