1998 chevrolet cavilier , ets light and check engine light on . One or the other starts it and the opposite follows immediately . Either can and does come on first , the only change in the driving I notice is the transmission slamming into the next gear . Not shifting good at all , very scary slam?

. Check for any engine and/or transmission codes.
. Ensure spark plugs (ACDelco only) have been recently replaced.
. Ensure fuel filter has been recently replaced.
. Ensure transmission fluid and filter have been changed within the last 24,000 miles or 24 months.

If problem persists, check/replace the Ignition Control Module and coils.