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Old 06-30-2009, 02:49 PM   #1
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97 4.0l error code 72

Hey guys,

I'm looking for some thoughts and insight. My 97 Sahara popped up a check engine yesterday. Today i drove it to work in the morning with no problem. Looked up the code listing and checked it at lunch. It is giving me a (72) "Catalyst efficiency below required level. (Same as code 64)".

Now, I am driving home on lunch break and she starts hitching or dropping power occasionally. I let it sit for 30 min at home. Come back out and everything starts up fine. The code is still there so i take it around the block and it is pretty rough dropping out like it may stall. Then it is ok for a bit and goes to rough running again. Pulled back in drive way let it idle and it was all over the place.


History: 200k on it. Fresh rebuilt transmission, Cleaned IAC a while back and took care of idle problem. Has 250miles on new plugs, wires, dis-cap, rotor, air filter, Crank sensor. All has been good since the tune up till now. I do have a cracked exhaust manifold and a leaking valve cover gasket, but they have been there from the beginning and never affected normal running before.

??? Cat, O2 sensors, Exhaust, Something else????

Thanks in advance.
MAYHEM -2014 Black JKU, Ballistic Jesters, 3" Rancho Sport lift, 35x12.50x17 Fierce Attitude MT, Nfab step bars and more items on the wish list.
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Old 06-30-2009, 06:13 PM   #2
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I would check the temps in front and behind the cat and also the temp of the cat itself.If the cat is much hotter that the pipe in front of it,it is clogged.If it is 100* or more hotter then something is causing the engine to run too rich.This should be done after running the engine for about 20 minutes.Check the temps and let us know what the readings are.If you don't have a thermo gun find someone that is into nitro powered R/C cars.They will have one.I just noticed you had an idel problem before,,,,Was it running rich then??? If so that will burn the cat out.

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Old 06-30-2009, 08:03 PM   #3
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I would guess a clogged cat also

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