Will a bad EGR valve hurt fuel mileage?

Ive had the same problems for 2 years now. As soon as temp's drop below 40 or 50 degrees I also lose a full MPG, WW Williams in Atlanta found nothing wrong and gave me the option of replacing EGR or the V-Pod. I replaced nothing, as I don't wanna throw money at it for nothing. I did talk to PDI about it, they recommended getting the ECM flashed which is being done now while I'm on vacation. If you find something please post it as I will do the same!!

 

My '04 does the same thing. Bad cough/miss/smoke and the fuel mileage is terrible. Then eventually the ECM logs a code, turns the CEL on and the engine runs smoothly, MPG goes up. It will stay like that until power is somehow interrupted, resetting the ECM. I guess the ECM eventually figures out the EGR is cycling way too much and shuts it off, logging a code. We may do the resistor mod to throw it into permanent boost mode.

 

One thing worth looking at is check out the website www.egrtuner.com and give that a try. I don't own a Detroit, but I know of a few people that have gone this route.

Seems the EGR flow is also tied into an altitude sensor. Like when in high elevation, the ECM basically turns off the EGR flow. The EGR Tuner is supposed to reset the altitude sensor so that it always thinks it is in high altitude and therefore shuts off the EGR all the time. The cost is not that great compared to other tuners and such on the market. I think it is only around three hundred bucks. Heck of a lot cheaper than going with a complete ECM flash or similar, unless one is really wanting big power as well.

 

The problem with this solution is it also limits how much boost the VG Turbo will produce, which then limits the horsepower of the engine

 

My observation is ECM limits VG turbo rpms by opening turbo wider which lowers the boost in turn. In other words variable geometry turbos work a lot on their rpm safety limit (90,000 on my ISX) thus they are maxed out when comes to efficiency any given time engine is loaded. Boost doesn't matter anymore since increasing it would take them beyond their limits. Its just different than old school turbos - boost can be build any time by closing the sliding vanes.

 

by definition, an EGR hurts MPG.

 

Have you looked at this? http://www.thetruckersreport.com/tr...teen-wheelers/152719-detroit-power-boost.html