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Discussion Starter · #1 ·
In my 1988 YJ with I have the 4.2 engine block with the 4.0 head. The intake and exhaust manifolds are stock to the 4.2 I believe. I have nuttered the Jeep, therefore I am not using the knock sensor and coolant sensor in the intake manifold and the oxygen sensor in the exhaust manifold. I would like to remove the sensors and switches and install plugs. I am having a mess of time finding appropriate plug for these ports. Do y'all have any suggestions where I can get these plugs?
 

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The oxygen sensor is M18 x 1.5 thread. If you google oxygen sensor bung caps you will find lots of choices. Some oil drain plugs are this same thread so a decent auto parts store should have something on the shelf that fits.

I believe the coolant sensor is 3/8 NPT thread so any local hardware or box store should have pipe caps that fit. I have no clue what size the knock sensor is but would not be surprised if it is also a NPT thread.
 

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Discussion Starter · #3 ·
Thank you Boojo35. Really appreciate it, gonna head to the hardware store. I went to a local Ace Hardware already with the actual sensors and switches in hand and they had nothing, so no Auto stores, Amazon, Home Depot, etc. I will get it now that I know the sizes.
 

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I went to a local Ace Hardware already with the actual sensors and switches in hand and they had nothing,
They "had nothing", or didn't bother to look, because it was an automotive fitting?
It wouldn't surprise me if it was a lazy somebody that had no clue that many auto fittings are nothing more than standard NPT pipe fittings, and just said "we've got nothing like that".

Ace better have pipe fittings, or it's not much of a hardware store.

Roger
 

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Discussion Starter · #5 ·
GTS225, it was really on me, I was looking for a bolt, I did not try to get a plumbing plug, so I was "DUMB". I will take care of this tonight. Thanks.
 

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Fair enough. Although Boojo says the oxygen sensor is an 18x1.5. Sounds like a metric bolt thread to me. Can't guarantee the Ace will have something that big, but you should be able to find it locally, somewhere.

Roger
 

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I foggily remember using a nickel, JBWeld and some part of a bushing or part of one of the sensors when I did my dual sensor elimination on my 4.2. Sketchy I know but I was in LA, Lower Alabama at the time, two hours away from anything
 

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Fair enough. Although Boojo says the oxygen sensor is an 18x1.5. Sounds like a metric bolt thread to me. Can't guarantee the Ace will have something that big, but you should be able to find it locally, somewhere.

Roger
It is a metric thread and it is a common oil drain plug size and as previously stated, any decent auto parts store should have it in stock.
 

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Can you share what all sizes you bought? It may be helpful to somebody else down the line.
 

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Discussion Starter · #11 ·
I used the following to plug the O2 sensor in the exhaust manifold (https://www.amazon.com/dp/B07DKGFVXP?psc=1&ref=ppx_yo2_dt_b_product_details). This came with a copper crush washer.
I used the following to plug both holes in the intake manifold (https://www.amazon.com/dp/B07DN1JLD1?psc=1&ref=ppx_yo2_dt_b_product_details).

I used Permatex high temperature thread sealer to prevent any leaks out of the manifolds. Especially since the water jacket actually connects to intake manifold and runs coolant through it in the 4.2 version.
 
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