Not really a question but a fix! My 1994 B4000 automatic 2 wheel drive was surging the rpms to 3000 rpms in park and in drive. I thought it was the IAC but it turned out to be the Coolant temp sensor. It costs me 15.99 at auto zone and now it runs great! As you can see I have a ton of miles on this truck and still have the original engine and transmission. The body is perfect and drives like a dream. I do have a "tick" in one of the valves which I can't get to stop ticking until it heats up but other than that its a DAMN good truck! I hope my "FIX" will help others. My email is erichbugman@yahoo. Com. Have a good day.
Thank you for sharing. For any problems a little diagnostics is required to get to the source and quite often people do it the esay way, it seems, replacing components hoping that it works. A wrong approach and wasteful way of trying to fix problems.
The tick that you are refering to should be the valve lifters and at the mileage you have, it is not surprising that one or more could be worn or at lreast requires some cleaning.