hey all, bought my 04 qc hemi 4x4 in may and was getting around 14 city 17 highway. yesterday it turned 49000 miles and while driving kids to school my CEL came on. i scaned it when i got home it was code P040? don't remember but it said to check egr performance/parameters. cleared the code and 50 or so miles later no code yet. would this explain why i'm getting 12 city 15 highway now? i researched this site and found much info on this, i also priced new ones 75$dealer/50$ autozone. if i clean the old one will i need new gaskets? is it worth it to clean the old one or just buy new with 49000 on it? sorry about the length of this but i'm still learning about my new toy and if i can save some money all the better. the truck never had drivabilty issues and still doesn't. it's also all stock. thanks in advance, carl

 

Just get a new one. And YES, a bad egr can kill your mileage.

When the PCM decides to recirculate exhaust gas it does two things- send a signal to the egr valve to open, and it retards the timing to compensate for the hot exhaust being introduced to the combustion chamber.

With this understanding, let's look at how the egr causes problems-

When the egr goes bad it can either stay open all the time causing the engine to run lean which causes the o2 sensors to tell the pcm to dump more fuel, or it can stay closed even when the pcm is pulling timing. Either way, the truck runs bad and your mileage goes kaput.

 

True story..

 

Yep, the TWO largest killers of fuel economy on the Hemi are an EGR not functioning properly and a dirty throttle body. Replace that EGR and clean the TB at the same time and it'll probably do wonders for your MPG's...