I'm having some major hesitation issues.
Whenever I put my car under load it starts missing.
It gets worse, the warmer it is: At night when it's in the 60's, I have to close to floor it to see the problem. But in the afternoon when it's in the 90's, when it's at its' worst, anything above 1500 rpm on a level road will cause it to start missing. Give it more than 1/4 throttle and it'll miss so bad that it stalls and shuts off.

Any ideas?
I've got a 98 s70 glt

 

What have you done to cure the problem?

 

So far, other than ask the forum for assistance, nothing. I'm on my way to get a code reader as my check engine light is on.

 

Pulling the codes is always a good start... when was the last full tune-up (i.e. stage0)? That may just fix it.

Does higher heat also correspond to higher humidity? If so, then suspect secondary ignition break-down; that could mean anything between the coil and the spark plugs.