Hello everyone. This is my first tie on the forum. I am the owner of a 1999 Blazer 4.3L 4WD. I have been having the same problem for 8 months or so. Over the past few months it has gotten progressively worse. Once the vehicle warms up and I reach cruising speeds is when the problem starts. If I press lightly on the gas or start going uphill, the RPM's start surging. I'll normally be around 1500 RPM's when driving at constant speed. Then the engine will jump up to 2000-2200 RPM's real quick and then drop back down to 1500. Sometimes are more severe than others, but it happens every time I drive. The engine overall runs alot rougher than it used to. It seems to not be as responsive anymore. The vehicle has died on me about ten times over the past few months. What happens then is it will be off for a few minutes, then start back up again. Then it will run for a couple more minutes, then die again. Usually if it sits overnight, it will run again, but the RPM surging never lets off. Most of the times the vehicle has died, it has been in wet conditions, but once or twice it has been dry outside. One time when it died, I drove through a huge puddle of water on the road, and it didn't start for a week after that. I am at my wits end with this Blazer. I have replaced the battery, alternator, Throttle Position Sensor, Crank Sensor, Fuel Filter, and done a complete tune-up. I have been told that the problem could also be a coolant sensor, a cam sensor, a vacuum problem, or a cracked head, But I cant afford to keep shooting in the dark. PLEASE HELP ME!!

 

Sounds exactly like my problem with a '97. Did you get a possible cause or fixit reply? I shudder at the thought of taking it in to a transmission shop. That could get ugly!
Good luck with your ride!

 

The stalling turned out to be a problem with the mass air flow sensor. As for the surging problem, it turned out that the tranny fluid was slowly leaking into the transfer case somehow. A friend of mine had rebuilt the tranny last year, so he's taking care of it.