Modifying my Brick-On-Wheels

[theholycow]

30mpg from an automatic SUV rated 15 combined? 24 at 55mph is a miracle.

[MTUboi86]

Yea, I can hardly believe it myself.
The highway estimate is 18mpg, even before any mods I got 19mpg going 55-60mph, but 17-18mpg going 70mph.
From everything I read, fixing the EGR valve shouldn't have done THAT much for fuel economy on the highway. I don't know if it's because it's functioning correctly now, or if it's because my check-engine light is no-longer on because it's fixed.

I really have no clue about the accuracy of this statement: I read somewhere that when your "check engine" light is on, your car's computer goes into a default mode and doesn't really pay much attention to the sensors, and gas consumption is higher (basically the default mode when you reset the computer??)
Anyone else hear of this? It would make sense... but I really don't know what the "check engine" light being on does, other than tell you something isn't working.

[Jay2TheRescue]

At least with the older models, like my Buick, when the Check Engine light is on, the car defaulted to a "limp home" mode, and ignored the sensors. Newer models may take some sensor readings, but I'm not sure.

[theholycow]

Some (maybe an old one like yours) might do that, but I think most only go into "limp-home" mode if there's something seriously wrong that could damage the car, rather than any time it throws a code.

[MTUboi86]

If anyone is interested, I am putting my Explorer up for sale. It's an unfortunate ending to this thread as I've had fun and enjoyed tinkering with it. The main reason I had it was because of it's 4 wheel drive, but now that it's broken it does me no good. I can't afford to fix it, so I'm cutting my losses. If you're interested at all, take a gander at my eBay classified listing and/or Craigslist posting below:

eBay

Craigslist

Thanks everyone for all of your input, help and comments on this thread! I appreciate it.