Fuel mileage

My 4.0 has started to get terrible gas mileage. I’m the original owner and it has 219,000 miles on it. Not too much has been done to the engine. It’s in really good shape. Just put new plugs,coils, air filter and change the oil and the plugs were set at 44 and I’m only getting 13 miles to the gallon. Does anybody have any ideas why my fuel mileage is so terrible.

 

Clean your MAF and throttle body and see where that gets you.

Have your driving habits changed?

 

Look for an exhaust leak near one of the oxygen sensors

 

Running rough, performance decreased? It's not unheard of to get a bad plug, coil, etc. Wiring all correct? Bump a vacuum hose? Start with the simple stuff. No check engine light?
Do an OBO scan to check for a possible sensor issue or....? Good luck, and know we really like to hear the end results!

 

Did the poor MPG start after replacing those parts? Or were the parts replaced trying to fix the MPG issue unsuccessfully?

I agree with doing an OBD scan. Need to make sure the engine is getting into closed loop mode. Is it warming up to operating temperature?

 

I did a tuneup on my truck because of rough idle and poor fuel mileage. I changed the coils, the spark plugs, the air filter, and I ran two fuel injector cleaners through the fuel system. The rough idle cleared up but my fuel economy is still bad. The first time after the tuneup my tank was 1/2 full and I put 1 can of cleaner in the tank and filled it with premium. I ran that tank down to 1/4 tank and added 1 more bottle of fuel cleaner and filled it with regular 87. This last trip to the gas station took 3/4 of a tank and my fuel per gal was still at 13 mpg. I use Costco gas and my driving habits have not changed. I took my truck to my friends mechanic and he put it on his machine and said that my injection system was working within standards and my pressure's were ok. I was thinking about taking it to the Toyota dealer and my friend told me to join this site and see if I could find some good advice.
I’m new to this site and have been having trouble logging in. Thanks for any advice or help.
My name is Mark and I live in Vancouver, WA
“I used OEM Denso parts”

 

I would do try fuel filter next, then try lucas oil injector cleaner when ur gas light comes on or a low tank. (I know its bad for pump to drive on an empty tank) push the engine a bit while the cleaner is in there and then fill up after. when I did this in my own I definitely noticed some smoother driving at higher rpms and upon acceleration. When I first bought my truck I did run some of the injector cleaner through and notices no differences... this time there was. I think a dirty filter takes away from injector cleaner and what its capable of doing.

 

As a point of reference for the OP; I just drove my '09 4.0L Access Cab from Ft Myers, FL to Boston, MA. The trip was about 1600 miles. I got a 19.5 MPG measured by looking at the trip odometer and dividing by the number of gallons that I pumped to refill the tank (some tanks as low as 18.5, others as high as 21). Using my BlueTooth OBDII port reader, and the OBDLink App, it showed that I was getting a consistent 20.1 MPG using the "Total fuel economy" PID.

 

I'm skeptical about it being anything to do with the fuel filter. It the filter problem was a severe enough factor to cause an mileage issue it'd likely be fuel starvation since filters tend to restrict over time and if it was restricted fuel pressure would be affected. The fuel pressure regulator is a factor in that system also but again, if it were bad fuel pressure would be affected. Sounds like that was checked.

 

Where did the oem denso parts come from? I ended up with counterfeit spark plugs from Amazon.

 

Were the plugs iridium?

 

At this point I'd clean the MAF sensor like dinosaurus suggested, not sure if it will improve things but it's a quick and easy job and it directly relates to fuel delivery. Not much to loose and if it's never been done it's overdue at 219K.

 

Clean the TB and MAF. The 1GR-FE engine is super sensitive to a dirty TB. I also recommend resetting the computer by just disconnecting the battery terminal for a few seconds. That will force the computer to relearn the A/F ratio with your tune up.

did you happen to get larger or heavy tires or a roof rack? I saw those affect MPG a lot.

 

OP, I don’t think you mentioned if the MPG was just drive around locally or strictly highway. It makes a huge difference. There really isn’t a fuel filter to change as the sock that is the filter is installed directly on the fuel pump inside the gas tank so unless your fuel pump is bad, you’re not gonna pull down the fuel tank to look at the pump to replace the sock filter

 

Im understanding what your saying. In my case, I had good fuel pressure as well. ended up buying a filter with the LBJs I went to the dealer for. I did notice a change in fuel economy, and also a pass of injector cleaner did much more than it typically would have after. My filter was long overdue, but if it hasn't been done which Mark didn't say in his post if it has or not, it should 100% be checked/replaced. Again I'm sure it varies on situation

 

The 4.0 doesnt have a canister filter like that. It has a fabric “sock” that wraps around the pump intake.

 

well that's pretty dumb. can you even access the pump without dropping the tank?

 

i gained 2-3 mpg with MAF cleaning, new air filter and throttle body cleaning

 

No, but it’s not a maintenance part, so no need to access it. It’s not fine enough to get clogged.

 

that's filter isn't reflective of the OPs filter design and most modern vehicles.

how many filter issues do you read about on here? Almost none, almost the entire industry uses in-tank filtration for gasoline vehicles and it's made the majority of fuel filter issues a thing of the past.