I have an '02 4.7 Quad cab. I just bought it, and the previous owner has done several upgrades to it. The biggest ones are:
Full exhast upgrade
Cold Air Intake
70mm Air Intake
Jet Stage II performance Module

My mileage over two full tanks has only been 11.5-12 mpg. Manufacturer specs say it should be around 20 mpg. So I am losing almost 150 miles per tank, which is pathetic...

The only thing I can think that would affect my mpg significantly would be the Jet Performance Module, but when removed, my mpg didnt really increase at all.

Anyone else have comparable engine mods, and lost that much mileage? Any advice? I love my truck, but at $2.50 / gallon, I REALLY need the lost mpg back...

 

Start with the basics. Oil change, tune-up, check tire pressure, check alignment, clean air filter (if reusable, it not, replace if it is needed), check belts. I would guess the drop in mpg would be due to the 70 mm throttle body. This is going to make your motor eat up more fuel to even out the air/fuel curve.

 

I was just wondering what grade of fuel your using?If it is a stage 2 they were made just for the high Octane gas.The stage 1s could run the 87 octaneStage 2s can not run no less then 89 it says it prefers 91 but can get away with 89.This could be why the drastic drop.The 70mm body will suck a couple not that much thoe.Also dont know if there is that much dif in the 02s from 03s but my Fuel rating is 15 in city 17 on Highways.I have a 2003 Quad cab slt 4.7 litter with few mods.

 

o2 sensors my man, replace them.

 

I suffer from the same problem. My 2003Dak 4.7 Quad 4x4 has gotten horriblegas mileage since Ibought it new in 2003. Recently I did the K&N CAIand Magnaflowexhaust, and my mpg got worse. On a good day I'm getting around11 mpg, andit really SUCKS!!! I have yet to replace the O2 Sensors. But right now I'mthinking that might be my next option.

For both me andpunkwood2k...does anyone know a good place to get them?

And, how many O2 Sensors are onour trucks? I know about the one by the Cat, but are there any others I/we should know about???

 

Replace the O2 sensor

 

There are two 02 sensors. One before and one after the cat.

 

The O2 sensor after the cat converter doesn't do anything except tell the ECU if the cat is working. It doesn't impact A/F ratio at all. On the LA based magnum engines there are only 2 O2 sensors, but I'm not sure on the newer overhead cam motors, there might be more. I went to napaonline and partsamerica and found the best price for mine, then printed it out and went into the local napa store and they matched the price. It was about $90 for a direct fit one. You can get a universal fit one and wire it up yourself for about $60, but I didn't want to introduce any more splices than needed.

 

This is true. However, it is responsible for many Check Engine lights. For future reference (Horatio, I know that you already know this ) if you get a check engine light and it throws a Cat Inefficency code, do yourself a favor before you run out and spend a whole bunch of money getting a new cat installed. Buy or borrow a heat measuring device. (I prefer the laser heat indicators) Measure the temperature before and after the cat. The temperature should be higherAFTER the cat. If it is the same temp on both sides of the cat, it needs to be replaced. If it is hotter post cat, then it is the downstream O2 sensor that needs replacing.

 

I might be wrong, but I am pretty sure that if the O2 sensor is malfunctioning, it ALWAYS throws a check engine light on.. My check engine light doesnt light ever. Any way to check an O2 sensor before I throw a bill at it?

Also, I dont think its the Jet Module. I took it out, put a tank of fuel through my truck, and only got 1.5 mpg increase. Slightly better, but not enough to offset the extra power I have with the Module installed. I'm going to put it back in.

But yes, I have fresh oil change, recharged K&N filter, good air pressure (I love Nitrogen in the tires, hardly ever lose any pressure)..

maybe I'll throw down the dosh on a new O2 sensor in a couple weeks. Its the Pre-Cat sensor I need to replace, right???