2001 hyundai perfect on Thurs. Engine light flicker, sulfur smell, rough running, low power on Fri

Hi - 2001 hyundai Elantra 97000 mi. perfect on Thurs. Engine light flicker, sulfur smell,
rough running, low power on Friday

First thought / hope, Bad gas? Had Filled up on Weds… I added dry gas and FI Cleaner.

Second thouht / fear Cat. Converter

Third . … . ??? Any ideas / suggs. Thanks!!!

If the ENGINE light is flashing the computer is warning that there is a serious problem that could be narrowed down somewhat with a code reader. Has the timing belt been replaced? A timing belt one slot out of time will cause your problems.

Hi - good advice, thanks. Did belt around 60K. This time it Turned out One Cyl. wasn’t firing. New plugs and wires got me rolling. Thanks.