So i bought truck used. It gets driven once a week if that and not very far at all. Has about 108k. Drove it today to the store, no problems. Went to leave and as soon as I put it in reverse it started shaking and the sound of the engine changed. Turned it off and on again same thing. Did the same thing while driving. Went to auto zone and on the way check engine light came on. put some fuel injector cleaner in it and filled up. Still same thing. Any ideas? Temps all good, no changes in rpm while idling. It did this once before but the rpm would dip real low in idle, put some cleaner in it and it went away immediately. Thinking its gotta be a misfire. Thanks for any feedback!