4" whoa.. that seems a little long for decking screws even with 1 1/2 decking.

You must be using ipe (iron wood) if you're finding that much of a prob, but anyway.. look for what's called a countersink bore it'll be a drill bit which will match the screws head & shank and also make sure it matches the gauge of the screw like a #12 gauge 2 1/2 stainless... which in hardwood needs a 1/8 pilot.
http://www.bitsnbores.com/html/screw_sizes.html

Alter Eagle Construction & Design

After predrilling, try putting some liquid soap on the screw. This will make it tighten a little easier. Also, you may want to try one of those square head screws. You'll need to buy a special square bit for them, but you wont stip those.

just my 2 cents

Since nobody mentioned it I will....

I have better luck on decks with square (Roberts) bits. They don't strip as easily as standard phillips. Replace the bits regularly, they are cheap, because the square bits do strip over time as well. Use plenty of downforce on your driver drill to keep the bit in the screw tight.

I have tried the combination of square and phillips, not sure who makes it, but it didn't work as good as standard square.

Also I used some special screws on one deck that was for composite decking, they were called SPAX screws and used a Torx bit. They worked great, but were expensive and the composite is soft anyway.

I use either the square drive screws or the Torx head ones from GRK Canada

Happy New Year Everyone!

Thank you for your Excellent suggestions.

Altereagle
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In regards to 4" screws, I was working with a stair stringer and needed to drive a 2 x 4" (width) into the stringer (9.5" width) and figured that a longer screw would be better. Did try the countersink bits without much luck. Looking back, perhaps, a lag screw would have been a wiser option. The link you sent has been educational. Because of the pixs, I can now see and relate to what is available for what.

Hammerman
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Liquid soap! Got to try this one. When we say square head, that is different from Torx which seems to have a "star" shaped head...? Correct? I take it that they are for exterior usage? Thank you.

Hoganman
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Is the square bit you are referring to similar to the one Hammerman is referring to? Is composite also what they call MDF? Thank you.

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Here are other things I tried with the results:

1. Used electric 1/2" 800rpm power drill with manual chuck and side handle - same results with existing screws. Better results with more expensive Philips (Mustard colored exterior) screws though the ***** store did not carry 4" and had to use 3".

2. Used a boring bit (1/4") to create a "countersink" hole wide enough to let my extended screw holder attachment with the screw slide in and then applied sufficient downward force. Decent results thus far... cannot understand why it worked...but, desperation sometimes leads to "creative" solutions.

Thank you.

IN MOST CASES, IF YOU ARE USING A CORDLESS DRILL, THIS IS THE INCORRECT TOOL FOR DRIVING DECKING SCREWS. YOU NEED TO CHANGE TO A DECKING GUN WHICH TURNS FASTER RPMS. IF THIS IS A SMALL JOB, AND CAN"T INVEST, CHANGE THE SCREWS TO A #2 SQUARE HEAD,WHICH IS COMMONLY CALLED A ROBINSON SCREW. MAKE SURE THEY ARE A REGULAR DECK SCREW FOR THIS PURPOSE. I AGREE, I FEEL YOU ARE USING WAY MUCH SCREW FOR YOUR JOB