Starting in damp weather 1993 240 wagon, auto/od, 235k miles

Have you checked the oil,checked to see if dipstick and fuel cap are tight.Do you have oil spots on driveway? Those are the first things I would check,if oil is on driveway is it coming from the oil pan.It 'seems" it May be tied in with the oil change from 2 weeks ago

Does the temperature gage on the dashboard show that the car is getting warm?

I would say it is to do with the ignition system.

1st. Congratulations on having 235K miles! I've got another 50K to catch up to you, very encouraging. Try pcmforless.com these guys have a good rap for reprogramming Trailblazer computers, not very expensive either and can have it back to you in 2 days.

I have seen crank sensors go and leave no codes, but, likely the fuel pump is going away...they get hot and seize, then cool down and work again. I would not replace either without proper testing only because parts are expensive and there are other heat sensitive components in there. (coil etc) Be aware that it will check out good if it is running right while tests are being done.

Your problem is that the transmission has gone beyond it's life expectancy with 235k. A host of Internal complications can be expected; seals become brittle, clutch plates become worn, pumps become weak and etc. Any remedy outside a replacement or rebuild will be temporary and indefinite. I have tried, (with limited success) adding a pint of brake fluid to transmission oil to soften the seals. With 235k, it can't hurt and may get you some extra miles out of it.

they all last to 235k, you may want to get to a dealer soon.

I'd be tempted to pull cover off & check belt too, or a quick compression test, to see what it tells me.

Did you try your fuel pressure regulator?

Idle air control valve