Hey scotty, i drive a 2014 chevrolet sonic Ls with an automatic transmission and 110,000km, over the past year when im idling at a red light my car makes random thumps/rpms drop about 100-300 and go back to normal, it doesnt happen everyday maybe a a few times a week but i know its not normal and the car idles great when its not bouncing/thumping, changed spark plugs and serpentine belt, cleaned MAF sensor and new engine air filter, no check engine light, any advice would be helpful, thanks scotty you rock 👍
Well its hard to say what's causing it exactly but at least get your battery and alternator load tested because if either are weak it can cause weird issues like this. If both are fine have the car scanned with a dealer level(top of the line) scan tool. Nothing and I mean nothing can hide from a high quality scan tool and a seasoned mechanic. That should help narrow down the problem and I wouldn't be surprised if its something serious consider chevy isn't known for quality. That should get you going in the right direction.
Dont these things have GDI, a turbo, and super high compression? Could it potentially be carbon build up?
