If you bought a vehicle “as is” but the dealer not disclose that it had a bad converter, can you sue?

Texas does have a series of Lemon Laws that protect consumers when they buy defective automobiles.  However, the term "As is" for used cars, is usually held to mean exactly that-- "As is."  I'm assuming from the some of the issues that you're having with this vehicle, that it was a used vehicle.  The Texas Lemon Laws provide more protection to consumers who purchase newer cars that are still under warranty, rather than older cars purchases "as is."  This doesn't mean that you don't have potential remedies, just that they will be more narrow.  If the truck you purchased is a newer model, used truck, and is still under a manufacturer warrant you may be able to evoke some provision under that warrant to help you.  If the warranty has expired, your only other option may be to file a fraud claim.  It would be interesting to see how this vehicle managed to pass inspection before with these issues.  You should be able to track down who did, or did not, inspect this vehicle.  If the inspection sticker was tampered with, you will have a stronger fraud claim because the sticker is a specific representation (and a government record which cannot be tampered with).  Even though satisfying, the cost of a lawsuit may cost more than the amount of money that you need to fix the repairs... so do a balancing test before you decide to file.  You may also be able to file consumer complaints, for free, through consumer protection agencies like the Texas Attorney General or the Texas Department of Motor Vehicles.  Even though these agencies will represent you for free, their response time tends to be a bit slower.  A private attorney can probably get something moving a bit quicker.  Even a demand letter from an attorney may be enough motivation for the dealer to at least meet you half-way in getting the vehicle repaired.