Downdraft cover and grill grates

You can't modify gas appliances.

It is possible to remove the downdraft equipment from underneath your JennAir electric cooktop and still use the cooktop, but it depends on how the downdraft equipment is attached to the cooktop and whether there are any other issues that may arise from removing it.
Before attempting to remove the downdraft equipment, you should consult the user manual or contact JennAir customer service to ensure that it is safe to do so and to obtain any specific instructions for your particular model.
Some potential issues to consider when removing the downdraft equipment include:

1. Airflow: The downdraft equipment is designed to help draw smoke, steam, and odors down and out of the kitchen. Without it, you may experience reduced airflow and ventilation, which could result in lingering odors or smoke.
2. Heat distribution: The downdraft equipment may also help distribute heat evenly across the cooktop surface. Without it, you may experience hot spots or uneven cooking.
3. Stability: The downdraft equipment may provide additional support or stability to the cooktop. If it is removed, the cooktop may become less stable or secure.

If you decide to proceed with removing the downdraft equipment, it's important to follow all instructions carefully and to take appropriate safety precautions. You should also be prepared to address any issues that may arise as a result of the removal, such as by using an alternative ventilation system or adjusting your cooking techniques to compensate for any changes in heat distribution.
If you're unsure about whether or how to remove the downdraft equipment from your JennAir electric cooktop, it's best to consult with a professional technician or contact JennAir customer service for guidance.

where there is a will there is a way --correct you will break it - it is tacked to frame ---to remove it you need to tear apart the unit ---purchase a claw style part retrieval tool $4 at harbor freight -$11 home depot---lowes etc

The downdraft is electric so there must be something malfunctioning with it. It is a high volume downdraft fan that is to be vented to the outside. Could it be that something has clogged the vent hole up, not allowing the fan to evacuate the smoke?

While I am not a big fan of Jenn-Air, their fans are usually high quality if they are installed correctly, with the proper vent lines.

Is this the part you are looking for http://cgi.ebay.com/Jenn-air-Range-Grill-Vent-Cover-Chrome-Down-Draft-Vent_W0QQitemZ220536707181QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item335903186d

The poupose of either is to eliminate any smoke created by the range or grille and move as much of the cooking odors to the outside. I wouldn't use both at the same time, but if the hood is vented to the outside, it would be just fine to use only the hood. Aregular cleaning will be necesssary. The downdraft has limits as to the distance it will efficiently exhaust air. Flex hose should not be used. And excessive bends or vent length, cuts into the efficiency.

Typically the Jenn-Air has a grill on the left hand side and the fan is suppose to come on when that burner is turned on.

the only way is to block off/check the flapper., if your not going to use for the winter you can disconnect the vent from under the cabinet temporaily and close off there till you can gain access to check outside grill

How do you get the inside area of the vent clean from the grease and oils where the filter is?? I have a rectangular box style downdraft that the vent goes into the floor, I pulled the filter, but the box is to slender to get an arm into to scrub the grease....... does the bottom come off, or is it a sealed unit? How do you get all the brease from the bottom if you cannot reach it?

No. If it is really important order the grates and downdraft cover as replacement parts. This will be expensive probably around $200 - $300.