Need some help. I have a 2002 Chevy Blazer V6. While driving around 45mph the RPM's begin to jump causing the truck to lurch forward then drop back. If I speed up or drop below 45mph the issue stops. One person I had talked to suggested it being the fuel injector (of which is the 'spider' fuel injector system) but I get no check engine light. Does anyone have any suggestions or ideas what could be causing this issue? Also, I get horrible MPG.

 

does it only do it in overdrive or in normal drive as well? I'm thinking might be a tranny issue? sounds like an issue shifting maybe a belt or solinoid on the tranny?

 

Double and triple check the transmission fluid level. The down/up shifting happens when it gets about a quart low.

 

Mine is doing basically the same thing - only it's been rebuilt and the shop just serviced it last week to try to fix the issue ... so don't think the fluid would be low?

 

Same problem on my 04 blazer any ideas

 

You guys got any codes?
A crank sensor can cause that symptom.

 

I'll also add that you might want to look into the O2 sensor(they don't always throw codes). If it's not reading correctly then it will throw off the AFR and the tug of war between the TPS and MAP sensors will mess with shifting.
Just another path to look into.

 

I have no codes coming up when I hook up my reader. It only happens in OD. Idle is perfect and shifting is smooth it is just when the trans gets to OD that this issues occurs.