I have a 2000 Chevy Blazer V6 with around 120,000 miles. When im driving around 45 to 55 mph the rpms jump up and down. Usaually by 300 to 400 rpms - so if the rpms are at 1600 it goes up to 1900 or so; then back down to 1600 and so on. Im not sure if its a transmission problem or a fuel system problem. I put in a shift kit about 8000 miles ago and replace filter and fuild. Wondering maybe if the TB needs to be cleaned, fuel pump changed or if's something in the transmission it self.
If anyone has any advise would greatly be helpful. Thanks

 

I have a 2003 blazer and the same exact thing happens to me i have no idea why?

 

This is caused by the torque converter clutch unlocking and locking back up again. That speed is actually where the variable lockup happens and, depending on requested engine output (throttle position), the PCM will vary the lockup to suit the conditions. This will typically occur more when the engine *and* transmission are cold (ie not up to operating temperatures).

If this is with everything up to operating temperature, then there may be a problem with the torque converter clutch solenoid or line pressure inside the transmission. If it locks up properly when driving faster, then you probably don't have much to worry about.

 

I have a 1999 S10 Blazer and I am having this problem. Do you have any advice on how to fix it?