I have a 1995 S10 Blazer Vortex 4.3 engine with 148,000 miles. Recently I had a problem with it not wanting to change gears and accelerate faster than 40 miles per hour. I took it to a transmission shop who changed the transmission fluid (per my request) and told me the problem was a faulty speed sensor. This was changed out and fixed the problem until the other day when I noticed the car would surge at idle and driving. It would surge so bad it would shut off the cruise control. I thought it was again something with the transmission, so I took it back to the shop, but
they stated there were no codes in the computer to indicate it was a transmission problem. The problem again disappeared on its own. I have noticed it is better when the car is cold, vs. When it is hot. This week I took my family on vacation towing a pop-up camper. Shortly down the road, the truck would not shift gears greater than 40-45 miles per hour. If allowed to cool down, the problem would get better. To say the least, my vacation was cancelled and we made it home. I have also noticed it is worse when towing. Could this be a throttle position sensor? Or am I having a problem with the transmission? Just a note, also, I have a problem with the anti-lock brakes and a growning noise on the drivers side firewall. I think this is the anti-lock braking pump system. I have heard this is very costly! Any ideas?