Huge decrease in gas mileage...no codes
11-17-2013, 06:52 PM
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Huge decrease in gas mileage...no codes
So I did some major work on my truck lately and some much needed maintenance. I replaced the engine because my brother destroyed my other engine. I have also cleaned my intake, throttle body, and injectors. I replaced the injector o-rings, replaced the fuel pump and filter etc. I used to average 18 mpg highway and now I cant get any better than 11-12 mpg. I used an obdII scanner to check the ecu and there are no thrown codes or anything stored in the system. Truck seems to run fine, still makes plenty of power etc but I can't replicate the mileage I used to get before my engine overhaul. Any ideas?
11-18-2013, 04:16 AM
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Sorry, didn't realize my truck info was not shown. I have an '03 F150 Extended Cab with the 4.6 Romeo Engine and 5 speed manual. I replaced it with n '04 4.6L possibly the romeo vin...don't remember, with only 45K miles on the odo. The previous owner had the motor sitting around for a while and I found out about him through a friend. He replaced it with an LS1 swap because he was building a prerunner and wanted a better platform.
11-19-2013, 09:36 PM
#5
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Do you have a thermostat in your motor and is it the correct thermostat for the motor. If your engine is running cool, it will not give you the fuel economy that it was designed for. you could also be getting bad readings from certain of your sensors like the temperature sensor or the MAF sensor may be dirty and in need of cleaning. It doesn't cost much to check all your grounds to make sure they are clean and free of corrosion and you don't have any sensors that are not hooked up. I am also wondering if your PCM is not a correct match for the new engine you have installed. The PCM should be getting all the readings from your engine and adjusting the fuel flow to give you optimal fuel economy and emmisions control.
11-20-2013, 03:03 PM
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Do you have a thermostat in your motor and is it the correct thermostat for the motor. If your engine is running cool, it will not give you the fuel economy that it was designed for. you could also be getting bad readings from certain of your sensors like the temperature sensor or the MAF sensor may be dirty and in need of cleaning. It doesn't cost much to check all your grounds to make sure they are clean and free of corrosion and you don't have any sensors that are not hooked up. I am also wondering if your PCM is not a correct match for the new engine you have installed. The PCM should be getting all the readings from your engine and adjusting the fuel flow to give you optimal fuel economy and emmisions control.