Hi Guys this is my first post as I have been reading for awhile now here is the problem

I have a 92 chevy s10 tahoe blazer got it off someone everything runs great! only problem is while driving once I reach 25 mph the motor surges as it moves into 30mphs never acts like its going to die or anything just surges and moves on doesnt do it any other time other then at 25mph any suggestions where to start? I am in no way shape or form a car expert so dont know much so any help would be great thanks

 

for starters is their a check engine light on? if so id run the codes those r simple and can do with paper clip. but from experience sounds like a vehicle speed sensor or a bad temp sensor(sounds funny but the one on my 2.5 went bad and really made it run weird)

 

No Check engine light is on on Could you please explain how to run codes with a paper clip? that would come in handy hah also as I said before I am in no way a car person very much but I am having a great time learning and could anyone point me in the direction of where these 2 sensors might be at? Thanks so much!

 

Check troublecodes.net. They have a pretty comprehensive rundown on it as well as the codes applicable to your vehicle.

Does this surge occur during a shift? Maybe something is amiss with the transmission...

 

well it is a automatic so not really sure when it shifts but you know when this is going to happen everytime at 25 mph I've had it all the way up to to 80 and it runs great no engine trouble at all just right there but I figured if it was anything too bad I would have a check engine light come on Im gonna try and go to advance today and see if they can check my transmission but any idea how to check for codes on this model?

 

Does it always occur at the same speed regardless of throttle position? The 1-2 shift should occur at different speeds depending on throttle position (slow acceleration or hard acceleration) so that is one way to rule out or confirm a transmission problem.

 

yes always happens at the same speed if I get out on the road and punch it to the floor you can still feel it when it reaches 25 but its ofcourse not as noticeable when going normal speed but drving normal speed I never have to let up off the gas it surges then moves right on in and drives fine after that point

 

So it is independent of the transmission gear/shift, independent of throttle position, and from the sounds of it, independent of engine RPM... That makes me think it is something with the drive line. A worn out u-joint or cv-joint that is causing a bad vibration right at 25mph...

 

is there anyway to test these to find out?

 

If there is play at the u-joints, they need to be replaced. Get under your truck with it parked on a flat level surface (better yet, with all 4 wheels off the ground safely supported by jack stands) and feel for play at all of the u-joint locations.