my van has just had a complete tune up but it still continues to jump, jerk and stall. A new motor (not used) was installed 2 years ago and we have tried everything to stop the jumping and jerking. I have been told by several people that it may have to do with the catalictic converter. Is there a way that I can disconnect or by-pass it?
If you live in the USA, you cannot LEGALLY disconnect or bypass the catalytic converter. If you live in a state with emissions inspections, the modifications will be discovered. Also, you will pollute the air even more; the rest of us have to breathe that air.
Who are the “several” people who told you is is the cat? Are any of them qualified mechanics? Assuming the Check Engine Light is on, have you scanned for codes?
You cannot legally disconnect or by-pass the cat. If the cat is bad you need a new one, that’s all. I’d get a professional opinion about the cat. I don’t think it’s the cause of your problems.