Don't drive it with the valve off, scrub the passages and run it with the valve off just to blow out the chunks that come free. It will run like crap but you don't want to blow the carbon through the rest of the system if you can avoid it.
Flashing SEL/CEL actually means there is a problem that could damage the converter. There are a few things that can be, the primary one is a misfire as those dump raw fuel into the converter and they are not designed for that. It can easily cause them to burn out or glaze over inside.
I prefer seafoam or GM top cylinder cleaner as it seems to do a better job than most others.
Tuesday, March 27th, 2018 AT 10:36 AM