- Feb 25, 2014
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Warm up issue - if the MAP sensor reads wrong, it can cause a lean condition (or rich) and make it hard for the engine to warm up. It takes gas to heat it up.I misunderstood your original post. If you keep your speed at 48mph on the highway, and use some hyper mailing techniques, I can see getting almost 30. In the warmer months, I typically see 31-32 mpg in my duratec (5spd with 3.73 gears), but my highway speeds are 60-65mph, so I see more aero drag than you see going so slow.
As for your problems, I'm not sure. I don't know why the trans would have to be removed to replace the egr valve, but the duratec is still kind of new to me (I've had mine for just a few months). A clogged cat would definitely hurt your fuel economy and cause the engine to run pretty rough. If it's a cat, the question becomes why is it clogged? A stuck injector or valve issue could cause raw fuel to be dumped into the exhaust, which would melt the cat. You'd probably be able to see the converter glowing if it were bad though.
The fact that it won't heat up means the truck is staying in open loop, which is also really bad for fuel economy. Maybe the thermostat is faulty? I've read some threads about Duratec thermostat issues in the past. They can be problematic.
It definitely sounds like multiple problems, or one fairly serious issue to me though.
I won't know more until tomorrow or monday when it is rather cold in the mornings and truck sits all night.
I am debating on changing the t-stat to a hotter one. Might increase MPG. The 180F one seems a bit low. Have to investigate the pros and cons like what happens in hot weather with A/C on.