98 Sunfire Transmission Converter surge problem

[kbethke]

I have a 1998 Pontiac sunfire that surges in third gear. Transmission shifts fine through first two gears and when it gets to third gear and the transmission is warm the transmission starts to act funny. Seems if I try to maintain a steady speed above 70 MPH it feels like the transmission slips a bit. I have a 3speed automatic transmission with a 2.2 liter engine.

It seems like the torque converter is unlocking for a second the rpms climb.

I replaced the tcc solenoid and had it flushed out. but it still does it. The transmission shop suggested the throttle position sensor is faulty but the check engine light is not on. Just wondering if anybody else had this problem?