Baffling engine problem - '99 automatic

[rabbitracer]

New to this forum. Hi all :)

I came at first looking for a black 99 trunk lid (backed into an F350, nice sized ding, way to go me ) and then saw this place may be able to help me with a bizarre engine problem I have. Basically about a year ago I bought my frickin amazing little 99 black Miata. It's an auto (haterz gonna hate, the car was so cute and fun I didn't care if it was an auto) and was in good shape. No mods. About 115K miles, had had a tune up before I bought it. Fell in love with it!

A few months after I bought it, though, it started doing this horrible thing. When I start the car cold, put it in drive, and push the gas pedal down, the whole engine frickin dies. The car will lurch forward a bit - it's trying so hard - and then it just cuts out. Dead as a door nail. The battery light comes on sometimes when this happens, sometimes also the check engine light comes on. The weird thing is it's so bizarrely inconsistent. I have to get up early and let my car warm up a bit, in case it decides to crap out on me. I turn the engine off, let it run for a few minutes in park, start her up again, and then I can get it to finally move. The problem seems to be worse on rainy days.

The throttle is very slow too. When you push the gas pedal down, the car is so slow to accelerate. Strains especially between 0 and 20 MPH. Have to push the pedal to the floor basically to get it to go. Some days it's worse than others. Once it's up to highway speeds, it's fine, as far as I can tell. Nothing other than the 65 mph shimmy really.

So I will straight up admit I know next to nothing about cars. If you couldn't tell already. I'm learning though I fell in love with my little Miata and I want her back to normal so she'll last me for years and years. Any insight I can get here would be awesome.

[Flyin96M]

Do you have any details on what was done during the tune up?

[cone-cerned]

Are there any DTC's stored?

[VFR750]

Sounds like your idle air control valve has some issues in the AM (as far as the stalling goes). The 0 to 20 thing is probably just a Miata with an automatic.......

[shortshift]

A lean fuel mixture is one possibility (basically what VFR750 said). Perhaps a vacuum leak or a malfunctioning part. A vacuum gauge might help with the diagnosis.