I have a 96 4.3L Blazer and it has recently been giving me some problems. From time to time when I try to jump on the throttle to pull into traffic or get up to highway speed I get hardly any acceleration or it will rev to about 4k -5k before shifting. Also I noticed that when going down the road and it seems to just randomly decide to switch between 2 gears. I notice it does this alot right around 70 on the highway. Other times she runs perfectly fine and give me no problems.

I recently just replaced:

Fuel pump
Distributor cap & rotor
Serp belt and tensioner

My thoughts were that it may have to do with a throttle positioning sensor but not certain. Anyone have any ideas as to what could be causing this

 

How to Test a Throttle Position Sensor (TPS) on a 4.3L | eHow

You sound right about the tps being the culprit, test it just to be sure.

 

its the tps sensor i garuntee it as i had the same issue a few months ago with mine. the trhorrtle is calibrated by the transmission shifts almost like a old school kick down cable. change it with a new one and ur set.

 

Hmmmm,
Not trying to hijack but having similar issue except mine just started to not upshift unless i release the gas pedal. Like it will be in 1st gear at 3k rpm, i let up on the gas pedal and it shifts to 2nd and so on.
Would that also be the TPS or should I start another thread?

 

its ur tps sensor i garuntee it. change it out and ull notice a diffrence

 

tps and vehicle speed sensor control shifts, if the VSS is bad usually the speedo wont work. And like said before, the TPS is known to have issues. It may not be dead completely but it can get dead spots

 

+9000..and 1 intrawebz reps for you.

 

I just replaced the TPS last night and that didn't seem to help a whole lot. I think I found that problem tho as its pretty apparent. Just noticed a pool of gas under truck this morning and looked up and saw it all over the side of the tank. Looks like one of the lines may have came loose after the recent fuel pump replacement. Checked it for leaks before I put the tank back up but guess something happened. If I remember correctly I started having problems shortly after replacing it too. Makes a lot of since if the engine isnt getting the fuel at a pressure it wants due to a leak. Going to have to drop the tank a little and take a look