Re: CivicLX -2003 auto 68K - Sluggish pickup in cold start condition - diagonosis needed

Bottom line here is what I would do:
--Go to Autozone and have them read the engine computer for any stored codes. Report back. --Change out coolant using a reputable shop. Use Honda OEM
coolant only. Make sure the coolant is topped off in the reservoir. --Change out auto tranny fluid using Honda OEM fluid only.
Then I would be looking at checking the idle RPM, the EACV and the fast idle valve pictured at http://www.bkhondaparts.com/billkay/jsp/prddisplay.jsp?catcgry1=CIVIC&catcgry2 93&catcgry3MR+EX+ABS&catcgry4=KA4AT&catcgry5=THROTTLE+BODY&ListAll=All&vinsrch=no&systemcomp=Engine&prdrefno=&quantity=0&act=&count=0&hidSwitch=Switch&hidIrno=%7C013%7C017
More detailed responses to your other queries follow.

True regarding what the owner's manual says. My understanding is Honda recommends 5W-20 oil to improve overall fuel mileage for its fleet, and so conform with federal fuel economy requirements. It is still okay to use 5W-30, and in fact Honda is not allowed to void any warranty on the car if a person does use the 30 weight, despite what the owner's manual says. See http://motoroilinfo.com/ford-honda-5w-20-oil.htm
But 5W-30 is a heavier viscosity than the 20. For Chicago winters, I would have the 20 weight. On the third hand, could the 30 weight oil be contributing to this sluggishness? A tiny bit not likely to be noticeable around 25 degrees F.

I do not know how much you work with cars, but the above sounds like overanalysis by a relative layperson. It's a nice layperson's theory but highly unlikely. And no, there is no such indication.

Honda automatic trannies circa 2003 are known to have problems unless one uses Honda's OEM tranny fluid. I would change this out, if only for peace of mind on such an expensive part (the tranny).

On a 2003 Civic, yes, you should get a CEL if the O2 sensor is faulty. But unless this car has been abused, I do not expect its O2 sensor to fail at only 68k miles.
Furthermore, the engine control computer ignores signals from the O2 sensor until after warmup.

Do you have an owner's manual? If so, look up the maintenance required light in the index in the back. You will find instructions on how to reset it. Walmart did not do it because it is not their yob (sic). Walmart, Jiffy Lube et al. do not deal with this much specialization. If you do not have the owner's manual, then go to site https://techinfo.honda.com/rjanisis/logon.asp . On the left, click on "Owner's Manuals." Follow the pointers. Once you arrive at the pdf file, it may appear that only one page has come up. In fact, page numbers that are highlighted within the pdf file are links on which you can click to take you to the page. Also, in the upper right hand corner of any white page look for an arrow. Click the right arrow to get to the next page.
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