Replaced spark plugs and car won't run?

[Leo99]

I am sorry, your hypothesis does not sound plausible to me. There is something more going on there that has nothing to do with ECU settings on basically clearing of common "adaptives". Your last comment makes more sense, or you pulled a wire out of a sensor/coil/ect.. by moving stuff around.

Seeing as I didn't do anything except let it run for a few hundred miles and it went from sputtering to purring like a kitten, I'm confident of my root cause analysis.

I didn't touch the coils, just changed the battery. The OP did a bunch of stuff.

 

[Japanese]

I finally got an opportunity to do some work on my daughters 2021 Mazda CX-30...

Where did you buy your spark plugs from and are you sure they are the right part number for your vehicle?

 

[The Critic]

Disconnect the MAF sensor connector and see if it starts.

 

[pbm]

Another update: Yesterday I took the Mazda on a long drive of over 50 miles each way (well over 100 miles total)* and it never ran better. No codes reappeared so I’m thinking my problem is solved. The only thing I can think of is that cleaning the TB made the difference since that’s the only thing I did differently from my previous attempts at fixing the issue. Once again I’d like to thank everyone for their help….the knowledge on this site is very valuable.

*It wasn’t a joyride but rather a trip into NYC to pick up my tax returns. At current gas prices there’s little ‘joyriding’.

 

[lazarus55]

Fake plugs? Where did you get them?

This is way more common than one would think btw. Astute question. I’ve seen it twice

 

[iCurious]

Another update: Yesterday I took the Mazda on a long drive of over 50 miles each way (well over 100 miles total)* and it never ran better. No codes reappeared so I’m thinking my problem is solved. The only thing I can think of is that cleaning the TB made the difference since that’s the only thing I did differently from my previous attempts at fixing the issue. Once again I’d like to thank everyone for their help….the knowledge on this site is very valuable.

*It wasn’t a joyride but rather a trip into NYC to pick up my tax returns. At current gas prices there’s little ‘joyriding’.

If throttle body is dirty and the battery was disconnected, it will cause the car to either die or run rough. The reason being is because it has to relearn the throttle plate position. By cleaning the throttle body you are basically setting the throttle plate position back to default, hence the problem is gone.

 

[Japanese]

If throttle body is dirty and the battery was disconnected, it will cause the car to either die or run rough. The reason being is because it has to relearn the throttle plate position. By cleaning the throttle body you are basically setting the throttle plate position back to default, hence the problem is gone.

Yes, that mostly likely was his issues.

I disconnected my battery a few times last winter and every time after that was running horrible and staled at red lights. But the next day was fine. Then I read that after you disconnect your battery at the first start up you should hold the throttle at 2.5K rpm for a minute or two to reset the throttle position, so the ECU re-learns its idle rpm. I think that is mostly for drive-by-wire vehicles.

That procedure is specifically for Toyota 2AR-FE engine. But probably for other engines too.
But even if you didn't do it, it takes the ECU about a day to re-learn its idle rpm.

I forgot to mentioned it earlier.