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my truck is suddenly getting 6 mpgs. it feels like this thing is lugging everywhere, and the gas pedal vibrates terribly at low rpms. the most recent thing i did was the fuel pressure regulator, which helped it run a little better but didnt aid in my mpg problem. the only basic things i haven't replaced yet on this truck are the tps, iac, and the pcv valve. i know there's a ton of things that can go wrong, but iv covered all the basics; tune up, oxygen sensor, air filter, seafoamed it several times, cleaned the iac, one cat is gutted, the other one i had checked. i did a self test and heres what i got:
179- Fuel system was rich at part throttle Single, Right or Rear HO2S - Fuel control
556- Fuel pump relay primary circuit fault - Power / Fuel Pump Circuits
these next three i got while the engine was running:
116- Engine Coolant (ECT) sensor out of range - ECT
411- Idle speed system not controlling idle properly (generally idle too high) - ISC
167- No Throttle Position sensor change in "goose" test (must get at least 25% rotation) - TPS
-truck in sig. sorry for the long post, all help is appreciated.
well our trucks dont get the best MPG from the get go but 6MPG is really low, i would start thinking computer is acting up on this one...
yes i agree. one code said its running rich, and then theres a ect and a tps code. the ect and tps could cause it to run rich. i think my next step will be to replace the tps and then check the codes again.
Did you pull those codes with a reader? I would have thought that truck would have 2 digit codes so if you just counted the flashes maybe they're decoded wrong.
That said.. I don't think 6mpg is possible if all the EFI sensors were faulty so you likey have some other issue.. like the fuel transfer problem. Does the truck get the same mpg on both tanks?
With the nature of those codes reported I suspect an electrical issue such as bad ground on the engine harness or ECM, or even possibly (after ALL other possibilities have been eliminated) a bad ECM itself.
Did this problem happen gradually, or all of a sudden did your fuel economy drop and these codes pop up?
Did you pull those codes with a reader? I would have thought that truck would have 2 digit codes so if you just counted the flashes maybe they're decoded wrong.
That said.. I don't think 6mpg is possible if all the EFI sensors were faulty so you likey have some other issue.. like the fuel transfer problem. Does the truck get the same mpg on both tanks?
i did the codes by counting flashes. i ran a wire from the little plug to my neg battery cable. i dont think this is a fuel transfer issue because when i put gas in my front tank, it all leaks into my back tank. so i only use the back tank. the front is always empty.
Originally Posted by redmondjp
With the nature of those codes reported I suspect an electrical issue such as bad ground on the engine harness or ECM, or even possibly (after ALL other possibilities have been eliminated) a bad ECM itself.
Did this problem happen gradually, or all of a sudden did your fuel economy drop and these codes pop up?