Well being old and growing up in an era of carburators, computer control has gotten me again.

2018 Versa stick shift, 56,000 miles. I changed the battery yesterday, and had it disconnected for two hours while I cleaned the battery tray. I restarted the vehicle when fixed but did not drive it. Today, I immediately knew something was wrong, even from the first shift when cold. Dash shows no codes.

Upon starting from a dead stop the throttle seems to have a delay. It makes driving this manual transmission difficult. Something is wrong, but I don't know what it is. Googling and looking at YouTube, I see this car has an electric throttle body, and I suspect somehow this is the problem. Videos all tell of a re-learning procedure for new replacement ETBs, but can this existing part need a re-learn? What else could be the problem. I suspect this is a common problem in newer cars. Thanks!

I'd clean your MAF before trying anything else, and check your airbox for debris.

Cleaning the throttle body is standard procedure when searching for solutions, but I think the answer is different here. I bought this car new, and the engine has always run flawlessly every mile. The throttle delay happened suddenly, yesterday, when I disconnected the battery. I removed the battery tray and cleaned the tray and tray area. It dried out for more than an hour, and I started the engine briefly to make sure it would start, then shut it down.

Today it has the delayed throttle problem. Since the throttle and gas pedal are computer controlled, I think the sudden problem is electric or perhaps I bumped a hose or wire when the battery was removed? Totally unexpected problem. I think the need for the throttle body cleaning would make itself known gradually? Not that cleaning it would not be good for it. I don't really want to creat a second problem by damaging that somehow before I get the delay problem fixed.

I'll pop open the air box tomorrow and take a look. Filter is almost new. That might give me some access to view behind the ETB. Thanks!

Could this be a blown fuse? Perhaps there are some codes to discover that do not cause the check engine light to come on? I'll look into that tomorrow. I would think a shorted component would throw a code.

The MAF is on the airbox and not the Throttle Body, right behind your repair area. Even a piece of lint or butterfly wing will cause very bad behavior, because Nissans for the most part have no MAP to cross-check the MAF. The ECM simply has to trust it. When it lies, bad things happen.

Yes, I know where the MAF is located. I suspect a different issue though. Very ODD.

Changing your battery shouldn't cause this. I've owned a 2012 Versa and now I own a 2019 Versa. Both have had their batteries changed with no issues. You might check to see if your Nissan powertrain warranty is still in effect. I think it's 5 years or 60,000 miles which ever comes first. If your powertrain warranty is still in effect, I would suggest taking it to Nissan for a diagnosis. Maybe their code readers could pick up the issue. If the powertrain warranty is no longer in effect, I would recommend purchasing the Haynes manual for the Versa. They're not that expensive and can be found online.