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California98Civic · 07-06-2018, 03:19 PM

The acid wash technique worked. Here are my SMOG test results before and after. Remember, this CAT survived a leaking head gasket, 260,000 miles of operation, wildly bad chronic fuel trim problems, and it was showing the P0420 code as recently as last weekend. I will update the OP with technique details.

2012:

A couple days after this test in 2012, I got an O2 sensor code.

2016:

2018:

07-06-2018, 03:19 PM	#52 (permalink)
California98Civic Cyborg ECU Join Date: Mar 2011 Location: Coastal Southern California Posts: 6,299 Black and Green - '98 Honda Civic DX Coupe Team Honda 90 day: 66.42 mpg (US) Black and Red - '00 Nashbar Custom built eBike 90 day: 3671.43 mpg (US) Thanks: 2,373 Thanked 2,172 Times in 1,469 Posts	It worked The acid wash technique worked. Here are my SMOG test results before and after. Remember, this CAT survived a leaking head gasket, 260,000 miles of operation, wildly bad chronic fuel trim problems, and it was showing the P0420 code as recently as last weekend. I will update the OP with technique details. 2012: A couple days after this test in 2012, I got an O2 sensor code. 2016: 2018: Attached Thumbnails __________________ See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.