Hello Everyone, First of all I am new here and this is my first post! GREAT SITE!!

I have 99 Blazer LT 4.6L 4WD. Always have been good with oil,transmission and general MXat regular intervals. So pretty decent MX history on it. However, since I am not the all knowing Blazer guru I figured you all could point me in the right direction.

Ok, Here is the problem:
When I reach about 45MPH the engine seems to hesitate a little then the RPMS jump plus or minus 500 from where it's at. Usaully around 1500RPMs. While I am accelerating to 60MPH it still does it. If I ease off the gas at 50 and maintain then its ok. If I try to accelerate at that speed then it stumbles.
It does NOT if I accelerate real fast. Just seems to do it with normal acceleration. I'm thinking fuel sending unit/sensor or maybe even the injectors in the throttle body???? Any ideas??? Thanks for the help

Mark

 

I would be more inclined to think it was a torque converter lock up issue than anything with the engine. While it is doing this, what happens if you lightly tap the brakes?

 

It acts normal if I lightly tap the brakes, basically as soon as a lift off the gas it just sets at a normal RPM for that speed and decrease in speed as normal. Now if I try to accelerate or maintain between 50-65 it starts jumping again. At first it was maintaining just fine between 40-60 now it jumps a little while trying to maintain. You can tell that there is really no change in the transmission case, no noticeable whine or vehicle sudden jerking that would indicate a gear shift problem or any other as far as I can tell. Hope this answers your question thanks for responding!

 

I guess I should have been mroe precise in how I meant you should do this. Holding the gas steady, with your left foot, lightly tap the brakes. If the RPMs rise and stay there for a bit, then you have a torque converter lockup problem. I'm thinking this is the problem anyhow, but that would confirm it.

 

LOL, Sorry that makes more sense. I'll give that a shot tomorrow and let you know. If it is that, is there an easy fix to it? Thanks

 

It did exactly what you siad it would do, tapped the break and the rpms went just a little higher but stablized then off the break they went back to flucuating. So where should I go from here? if it is the torque converter is that an easy fix?

 

This could mean that the torque converter clutch has gone bad, or it may be a problem with the TCC circuit in the transmission (either electrical or hydraulic). If there are no transmission codes present, then I would take it to a qualified transmission repair shop and have them diagnose it. I hate saying that, but automatic transmissions are VERY complex. One thing that you really have to do is to make sure that they fully explain what is happening. If they tell you that you need to replace your transmission, tell them that you would rather get a second opinion.

 

Well, I would like to say thanks for all the help in troubleshooting. I got it fixed! With your help and a little troubleshooting believe it or not it was the trnas FLUID! Wow, talk about an easy fix. I was a little surprised that it was fluid considering it was replaced not to long ago however I found out living up here in -50 temps destroys the fluid life. So I have replaced it with a full synthetic fluid that last longer in lower temps. Hope this helps anyone else that has a similiar problem! Thanks!

 

Wow! Good deal! Thanks for the followup and glad you got it fixed!