Hello,
Sorry if I posted this in the wrong spot I wasn't entirely sure where to post since I don't know the exact problem. Okay so 6 months ago I bought a 2008 grand prix base with 123k miles on it in pretty good shape besides a dent or two. Recently while driving on the highway between 45-55MPH my RPM will randomly drop down by a few hundred usually between 1100-1300 & if I try to accelerate the car will either gain speed very slowly while the RPM's start climbing or the RPMs will start to actually slowly decrease more and the only way to get it moving upwards again is to floor the pedal, then it's okay. Sometimes it happens almost constantly, other times just once in awhile & it happens at faster and slower speeds but not as common.
The transmission fluid is at the correct level & looks light in color (not burnt) the transmission temp is usually 160-190 but I have seen it at 235F after driving for an hour or so in 90F weather (guessing that's probably okay?) I don't know if the fluid has ever been changed. Now a couple weeks ago I installed a new radio in my car & had the battery disconnected, after getting it connected again and driving around, the car didn't have the RPM issue for the next 3 days. Now it's back again. So far I have tried cleaning the throttle body, had 2 exhaust leaks repaired, looked for cracked hoses or anything obvious and haven't found anything. I'm considering changing the transmission fluid but not sure if that's a good idea or not? I have heard horror stories if the fluid has never been changed. Besides this the car runs great no issues with anything else.
I have a bluetooth OBD 2 scanner and the torque pro app and I want to test it out tomorrow and see if I can find anything. There is no codes or check engine light. If I have live data with the app, what sensors or things should I be looking at/recording while driving around?
Thanks!
