Transmission problem - RPM flares up from coast when accelerating

I have just started to have some problems with the transmission in my 98 Grand Prix GTP.
When I am driving along at steady state and accelerate lightly, the RPM will
flare up about 500 RPM and then come back down within a second or so. It seems like the torque converter lockup clutch is disengaging briefly and then re-engaging. I am suspecting throttle position sensor or a solenoid or... Who knows.
The car has about 200,000 KM on it and is otherwise in great shape. No other issues and runs very well.
Any thoughts on this are appreciated as I don't really trust many shops out there and prefer to do all the work on my car on my own.
Lorne Pickering, Ontario Canada
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This should be scanned by a trans capable scanner and look for codes and/or lock up operation and slippage, will all show on scanner.

will
other
out
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.