mileage dropped from 19 to 15, where to start?
 

In early spring I had the intake gasket fail and dumped all the coolent into the engine. Luckily it didn't blow but it pumped the coolent throught the pcv back into the intake where it got either burnt off or pumped out the exhaust.

I used to get a steady 19 mpg weather I was in town or hwy, loaded or empty. Now I'm getting a constant 15 mpg.

So where should I start? I had just replaced plugs and wires before the gasket failure. Could the plugs have gotten partially fouled? O2 sensors gunked up or cat plugged?

I guess I could just replace all that as I just turned 100k but I'd rather not waste money replacing stuff that might be fine.

have the codes pulled....it is possible for a code to be in the PCM, but not showing on the Check Engine Light.

also, it could be your driving habits have changed.

would Autozone be able to pull a hidden code if the CEL isn't on??

I pretty much only use the truck to go to work and back and hauling. I've tried driving for mpg and I've really romped on it. It's usually a pretty constant mpg.

Keep in mind, a MAF or O2 sensor on its way out may not throw a code.

^^exactly...

yes they will....if there is one in the PCM it will show up on any OBDII code reader...

x2, if no codes show up, maybe a tune up is in order. Wires, plugs, air filter, oil change(if not done recently) fuel filter and PCV change. -Mike-

Check the 2 easiest things first.

Clean intake box/filter.

Tire pressure.

Tire pressure.....good one. Something most people overlook.