Dodge Caravan 1999 3.8liter
Another story about a little engine that could. (First one being 1976 Chevy pu truck.)
Miles per gallon before “adjustments” & Gadgetman Groove:
13 to 15 miles per gallon
Miles per gallon after “adjustments” & Gadgetman Groove:
17 to 25 miles per gallon
30% improvement city
66% improvement highway
A used throttle body was purchased for $50 to allow the vehicle to be used while some of the “adjustments” & Gadgetman Groove were being made on used one. Dodge Caravans have the idle air intake at the bottom of the throttle plate, right in the way of the Gadgetman Groove location. This area needs to be filled in.
Remove idle air injection unit (2 screws) and throttle pedal position unit (2 screws) from throttle body to make things easier. Use paper towel pieces to cover up openings.
Thin metal roof flashing or aluminum can be used to make a dam pieces to form quick epoxy (5 Min.) to fill gaps from idle air pathway. This is necessary to allow for Groove. Also epoxy is necessary to build up thickness so Gadgetman Groove doesn't cut through to outside of throttle body. A large piece of flashing following inside curve of throttle body and a smaller piece on other side of idle air intake gap provide a dam to form epoxy. Also a little narrow strip lower down below dam in idle air chamber will keep epoxy from dripping down to much.
All areas in contact with epoxy need to be ground clean with small Dremel tool. The smallest can be used in the corners and the next size up can be used in the flat areas. Take just enough off to expose fresh metal.
With a small flat wooden stick (cut from a wooden shim) scoop up mixed 5 min epoxy and fill prepared area. After 30 min carefully peel back metal flashing forms to expose epoxy patch. Extra epoxy will need to be added to areas that are not thick enough or not properly formed. Don't forget areas outside the throttle body near the Gadgetman Groove that the Groove mite break through. If it does break through you can add epoxy and touch up the Groove carefully. File the mating surface of the throttle body flat with a fine flat file.
Cut the Gadgetman Groove into the throttle body being careful not to go to far up each side.
I have herd that up to a 30 degree angel can be implemented ( shaft of cutting bit 30 degrees up ) 15 degree minimum. Using a cup of water to cool bit and wd 40 to lubricate carefully work cutting bit (large) a little at a time. One can use a protractor and draw lines on paper taped to work table to help guide tool angel. Most of it is by eye and feel but reference lines help, you just have to take the leap.
In order to provide the idle air necessary to supply the engine with air at idle, one can install a small hose fitting (3/8 inch hose x 10 mm 1.0 thread pitch) drill hole & tap hole with fitting end requirements. Screw in with teflon tape.
Connect new installed fitting to intake manifold. A narrow hose clamp can be used in middle of new idle air hose to adjust amount of idle air flow through hose. The less the better, enough for proper idle. One can make an intake manifold connection available by re routing the rear valve cover vent line that connects to the intake manifold. Putting a elbow on the end of the vent line tube where it used to connect to the intake manifold and then connect rear valve cover vent hose to the front valve cover vent hose which connects to low vacuum side of air intake. Re routing rear valve cover vent from high vacuum side of intake manifold to low vacuum side eliminates a major vacuum loss.
A better way to provide the idle air necessary to supply the engine with idle air is to not use the idle air valve system at all. Instead of drilling and tapping in new fitting. By removing the cap on the throttle body throttle plate adjusting screw and simply turning screw in approximately 1.5 turns or enough to hold a good idle speed. This brings in necessary idle air.
With air conditioning, the idle speed needs to be slightly higher, around 850 rpm when air conditioning is off. To hold proper idle with air conditioning on and car in drive it needs to be around 650 rpm. Air conditioning causes the idle to drop slightly when compressor kicks in.
By bringing all idle air in through the throttle plate all the air into the engine goes past the Gadgetman groove giving the best possible conditions for highest vacuum. Any vacuum loss on engine side of throttle plate & groove reduces efficiency of the Groove. Any leaks in the intake manifold will substantially reduce positive effects of Groove. Resetting intake manifold with new gasket and sealant
will ensure highest mileage increase.
Some fuel injected engine throttle bodies don't have the idle air injection port in the way of the Gadgetman Groove location, the idle air injection system can still be a source of vacuum loss.
I hope this info is helpful, happy Grooving
