So I've got this 2003 V8, and when driving on the highway, particularly uphill, the engine sputters and coughs. At first I tried a can of dry gas but that doesn't seem to have helped.

The SES light was on for a while but a couple of weeks ago it went out, of course the day I was going to take it over to Advance Auto Parts to get the code checked.

From what I've read it could be a clogged fuel injector or it could be a bad coil, bad spark plug(s), or something else. What would you check first?

 

You have the codes read then you go after the problem. Once you code the vehicle, it will give you where to go and what the problems can be to each code. Example: P0308....#8 is misfiring. You would then pull the wire or COP and plug from that cylinder and go from there. This is the only way to keep from throwing a load of money into something that you want to fix, and only find that that wasn't the problem.

 

yep. diagnose the issue before you start throwing parts at it

 

You can get a basic OBDII code reader on Amazon for about $20 and save driving to the parts store.
How many miles on the vehicle and how long has it been since the plugs and boots were changed?
Definitely find out what codes, but my guess would be a misfire under load from a bad plug boot or plug.
The coils and injectors are less likely, but also possibles.
Does it idle and accelerate smooth?
You could be having misfires and it takes a lot of misfires to set a code.
If you get a code such as P0308, first thing would be to check the plug and swap the COP with #7 and see if the code moves to #7.
Check the PCV hose for cracks or soft spots, particularly near the throttle body where all the heat is.

 

Yep, 10 to 20 dollars will get you a wifi or blue tooth code reader on ebay. The days of an inexpensive code reader costing $200 is long gone.

 

The bluetooth or wifi code readers need software, such as Forscan or TorquePro, on an iphone, Android or PC to get the codes.
There is a a basic code reader on Amazon for $14.95 that will read the enine codes, display them on the unit and can clear the codes for a retest.