Could someone please help???

[vis_inc]

I have a 1996 Blazer auto trans 4.3 motor the problem when I get to cruising speed 50-60 MPH the RPM's will not stablize it goes up and down constantly roughly 500 RPM I have replace the TPS but no changes. It only happens when at 50-60MPH.

Please help me out here I need some advice with anyone that has had similar problem?

Thanks

[BlazerLT]

Torque convertor solenoid is failing and the truck going in and out of overdrive.

[vis_inc]

Is this the only symptoms which occur if a torque converter solenoid is bad?
How hard is it to replaced?
Thanks

[blazee]

It's most likely the torque convertor locking and unlocking. The condition is caused by wear in the valve body. The bore that contains the TCC isolator and regulator valves, wears and allows fluid to slip past causing poor TCC apply. GM sells an updated Valve Body that fixes the problem. There is also a repair kit (sold by Sonnax, I believe) that will allow you to repair your current valve body.

If the PCM detects it as a slip, it will command max line pressure, in which case you will notice hard shifts. If it is detected two times in a row, it will illuminate the SES light and store a P1870 code.

[vis_inc]

Turns out the problem was a tune up!

[BlazerLT]

What did you do for the tuneup?

[vis_inc]

Distributor Cap, plugs, and wires

[BlazerLT]

Ummmm,,,

You have to replace the ditributor rotor when you replace the cap, you cannot just replace one or the other.

Also replace the fuel filter, the PCV valve, the air filter as well.