I sometimes smell gas in the car. I resently had an oil change but sometimes in the morning it shuts off and the oil light comes on. Sometimes my steering wheel locks up when I use the defrost. I am missing my cap for the coolant. The van shakes when I drive it as well. I have a few things wrong but the evap system is the problem. Am I damaging the vehicle more by driving it. How much will fixing this cost me?
My car has 186000 miles.
My car's transmission is unknown to me.
If your vehicle has an EVAP system leak, the Check Engine Light will normally illuminate, because a Diagnostic Trouble Code has been stored, and the Mechanic can use the Code that was stored to start his or her Diagnosis.
The odor of gas could be from the EVAP system but there are many, many other possible sources of liquid fuel leaks (as opposed to vapor leaks in the EVAP system) in the fuel tank, fuel lines, fuel injectors and so forth that can account for fuel odors. If you do have an EVAP system leak, typically a low pressure smoke machine will have to be connected to the system in order to find the leak source.
Driving a vehicle with "most" EVAP system faults will not damage the vehicle but driving with LIQUID fuel leaks could be potentially catastrophic especially if the leak is under hood, near something hot, and if the leak one day becomes "large". So, the concern is not so much the vehicle but the potential for a fire or explosion that could hurt you.
With regard to the coolant cap, that is easy to resolve. The steering wheel locking up is a concern and should be addressed. I would say after the gas leak is addressed and the steering locking issue is resolved, after that the vibration issue can be diagnosed.
To avoid any unnecessary repairs, my advice is start with a fuel leak diagnostic by a certified technician, such as one from YourMechanic, and then deal with the other issues in turn.