Hey guys, so just bought a 2005 gmc jimmy, about 120 000 km on it. Been having a bit of **** luck lately with it. Had a check engine light pop up, and mechanic said it was the thermostat, but on top of that it started to have a rough time accelerating going from 40km to 50km and the rpms would drop. I was told it could be tranny so I had tranny fluid replaced , started driving better, but after an hour of driving it acted up again for a bit. Took it to a transmission machanic but he said he couldn't feel anything wrong with it, said he drove it for a couple hours, just brought it back home, going to keep an eye on it. Anyone got any pointers or past experiences ?

 

Can't offer specific help, but only general. The first thing is to try to diagnose the issues as best as possible.

The first step is to find out what the error code are that are making the check-engine light pop up. These can help identify what is not working properly.