2004, Auto Transmission (w/Tow feature), 6 Cyl Approx 78K miles

A few weeks a go, I towed an old tractor using a 18' trailer. Towed the tractor about 20 miles and then towed the empty trailer back. Temp gauge got well above normal during the trip. Before going back I let truck cool down and then towed empty trailer back.

Afterwards I noticed that my gas mileage has plummeted. Was getting 18-20 MPG around town and now 13-15. Unplugged the battery to reset the computer and aired up the tires but no real change. Twice since that day, I have had a check engine light. When I use the built in code checker (hold the Trip Odometer in while turning on the ignition) the code showed 00. Disconnected battery to reset 'code'. Couple weeks later it showed back up with the same info on the dash. Reset. A few days later it showed back up and then the next time I started the truck it was gone. NO check engine light currently.

Any tips on how I should proceed in troubleshooting this??

Thanks,
Mike

 

I take it the "6 cyl" is a Cummins? The major concern here is the overheating, I'd think. Was this in traffic? I'd start suspecting the cooling fan. Perhaps the clutch has gone bye-bye and is not turning properly under those conditions.

 

Go to Autozone or a local parts house and have them scan it with a real tool. There is something wrong or the light wouldn't have come on.

 

No it is the 3.7L V-6..... There was no traffic and I drove 45-50 MPH.

 

EGR Valve is probably gummed up...clean it or change it out.

 

I understand you might not have had a choice but why on earth would you even want to tow ANYTHING with a 3.7 V6?

Its normal for everything to run a higher temp when towing. You are after all, overloading it with more weight. As long as it didnt get critical I would think you are fine but I certainly wouldnt push it with a 3.7

As for the CEL, when it does come back on, as said above, dont reset it but take it to a shop and let them scan it for codes.

 

Let me guess...Your going by the Overhead console? The reason your mpg's plummeted is because you get much worse mpg's while towing and it recorded that! You certainly werent getting 18mpg while towing around town. I'll tell you that right now! especially not with a V6 where it has to work twice as hard as a v8 to pull the same weight. So, you were likely getting 10mpg while towing and it calculated the average as 13ish...
Ignore the console. Fill up and calculate your mileage that way. Niothing wrong with your truck. You were probably pulling too much weight with your V6 and it got hot!

 

I'm not talking about the gas mileage I got while I was towing. I'm talking about the gas mileage I got before I towed the tractor and what I get now after that experience. I'm not looking on a console, just calculating from miles driven versus gallons pumped

 

Gotta pull that code, a code reader will read "stored codes" so even if you don't have a CEL currently it can be read. Go to nearest auto parts store - they will scan it for free - then you'll have a place to start troubleshooting...

 

Maybe your 02 sensors are gettig old and tired...Also, your plugs should be changed as well. That would not throw a code and cause unneccesary consumption. Non-working sensors throw codes, poorly working ones don't all the time.
I say this because maybe you didnt calc you mpgs the tank prior to towing like you did right after towing. Most people assume coorelation after things like running hot with a rattle or a noise that they never really payed close attention to before.
All I'm saying is...Maybe your mpg's have slowly declined over the last couple of tanks and possibly you havent noticed it until now?