THIS NOT LEGAL ADVICE: There really isn't much one can do to stop a buyer from suing over anything, really. Section 24007 (b)(2) of the Vehicle Code states it is the responsibility of the seller to provide a valid smog certificate at the time of delivery of the vehicle. There is no provision in the law to sell a vehicle "as is" as it applies to the smog inspection. However if the buyer will sign a waiver, admitting full on that he/she is aware that the vehicle is being bought without a smog certificate because of a damaged engine or such, you should be fine with the sale. Remember though, if the buyer one day decides that they made a bad choice, they still maintain the right to sue you in small claims court to collect on any damages. A buyer would probably not do this sort of thing, specially after signing a waiver, but just keep in mind.
There is also the option of selling the vehicle as "Non-Operational". In this case you will need to place the van under non-op with the DMV before the sale. Vehicles registered as non-operational do not need a smog check during sale. The buyer can remove the non-op after paying registeration fees and obtain a 30 day temporary operating permit (for a fee) while attempting to get the van to pass a smog check.
