whats going on!

I have a problem that is baffling. One day I drive the van with no problems. Next day or whenever out of the blue,it starts running like a bucking bronc. Missing,and spitting,and STINK.Come to a stop and just about stalls. Not noticed to much at road speeds. Although it is probably doing then also. I have tried the gas additives,like fuel line cleaner or injector cleaner. No luck.About 2 years ago it did this for my wife,I went to tow her home,and it started and ran fine. Then again about a year ago. Now it is about two or three times a week. I am scared to drive it anywhere. Any help would be appreciated. Here are the details. 1994 GMC Safari 4.3 V6 244,000 miles. A very good van,and would buy another. Just having troubles right now. Thanks to all.

Maybe a new alternator. Mine did something simialiar and would start sometimes on the old alternator but if i drove it somewhere or let it sit while running it would start to act up and quit.

sounds real similar to what my 93 with 125000 miles did. the original thought was the fuel pump or blocked catalytic converter but turned out to be just a fuel filter in the gas tank. cost about $110 to fix at our local shop. dropping the gas tank was not a job I wanted to do.it did the same as yours sounds though including the frequency of happenings. usually was worst when temps were real hot or changed drastically for whatever reason.

Sounds like your EGR valve may be stuck open.

Check there first.