Removing A Factory CO Plug

All DeLoreans came from the factory with what was purported to be the proper fuel mixture setting, and the ability to adjust that setting was sealed up with a tamper-proof plug. This was a measure to prevent tampering with the screw underneath which was considered an emissions control component. Adjustments made here will affect the amount of carbon monoxide in the exhaust, hence the name CO adjustment screw. As many owners know, this setting may or may not be where the car is at its happiest depending on the atmospheric conditions where they live, the condition of the car, or any modifications that have been made. 

Luckily, the tamper-proof plug can be carefully drilled out and removed, allowing access to the fuel mixture adjustment screw. Once the plug is removed, the screw can be adjusted with a 3mm allen-head key - one with a T-handle is preferred, as it allows for more minute adjustments. After an adjustment is made, the hole needs to be plugged with a 102392A CO Adjustment Plug (#26 in the image below) in order to cap off what would otherwise be a vacuum leak due to the tamper-proof plug no longer being present.

To remove the factory plug, carefully drill a ⅛” hole as centered and straight as possible into the plug - you can do this without needing to remove anything from the car. You will NOT be able to drill completely through the hole and should not try. While the top of the plug is aluminum, there is a steel cap on the bottom so you should stop drilling as soon as you feel the resistance go up. With a small hole drilled, find an appropriate sheet metal screw that will bite firmly into the aluminum. Firmly thread the screw in as far as possible, keeping in mind that you will hit the steel plug and the aluminum will strip out if you attempt to thread it in further from this point. Now using a pair of long-handled wire cutters, grab the screw at the base and pivot the pliers against the metering plate housing to ratchet the screw and plug combo out of the hole. This will take a little effort at first but should then just pop right out.