Poor mpg

ColoYotaGurl

ColoYotaGurl

New member
I recently purchased my 99' and like I always do when buying a used car, went through an oil change and general tune up. Everything is running great and no issues, other than really poor mpg. I'm averaging 14.8mpg with mixed.city/highway driving.

Anyone have any easy and not to exspensive ideas for boosting mpg?
 
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When I first bought my 97 3 months ago I was getting 11! (eek!)

I did a tune up consisting of the following:
Oil Change
Filter
PCV
Plugs
SeaFoamed

I'm now averaging around 15-16 with mostly city driving which was a huge increase from the 11 I got on the first two tanks.
 
reset the ECU.

Do you have the factory remote?

I hauled a heavy load from Vegas to Louisiana. After that day my truck did the same! 13 MPG! Before this trip it did 20-21 mpg in NV and CA area.

I took off the battery neg. terminal. Press the brake and hold for a minute or two. Leave it over night. Connect the battery and turn the ignition to ACC and leave for 10 minutes.

Before you strat the car make sure AC, head lights and everything else is off and start the truck. It might hesitate to start. once it starts running leave it for 8-10 minutes.

What happens is reset the ECU to factory settings. It will take fresh readings from the sensors.

After this adjustment I did a trip 90 miles and took 5.2 Gal (65 miles freeway at 70 MPH and 25 miles city and 70 minutes parked with AC on. Impressive mileage!)
 
How do you reset your ecu. Im getting 10mpg and am doing oil change AND SEAFOAM thursday as a bday present to myself :) Tell us all your results after resetting your ecu please
 
One of my 3rd Gens was getting terrible mileage. I went through it: Seafoam, plugs, wires, fuel filter, air filter, PCV valve, O2 sensor and cleaned the MAF & TB. Still got awful mileage. Turned out, had a small exhaust leak. Fixed it, MPG's shot way up.
 
After the reset your fuel gauge acts crazy until you refill the tank to full. Remember ECU is brain dead so it needs all the readings from the beginning to give correct results. Just an update.

By the way. my truck has stock muffler, OEM spark plugs and wires, OEM air/gas/oil filters. 35 PSI all around. No vibrations, perfect wheel alignment/balance (Firestone lifetime $160!). Don't go beyond 70 MPH. Wind resistance rises exponentially with the speed! + 70 MPH is a safe speed for a SUV.

Have you cleaned your injectors? This is how I did. Use one STP bottle with 1/4 tank. Run until the reserve comes on (try to have high concentration). Then use another with a full tank and best results can be achieved at long trips. I only use SHELL OR CHEVRON regular gas.

Let me know how it did.
 
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i got terrible mileage on my first tank in mine, so i did the ecu unplug/reset and got about 19mpg on two tanks after, now this past weekend I got the exhaust leak I had fixed and it seems to have gone down, will have to see when i fill up later in the week and do the math though. maybe i need to reset the ECU again.

I should just cover the gas gauge anyway cause once this thing gets lifted and tires its gonna need filled up twice a week I can already tell.
 
After the ecu reset, oil change and mf/tb clean.. I got 16mpg on my trip. Not great but some improvement.

I'm going to clean my injectors and see.how that works.
 
PitbullRescuer said:
One of my 3rd Gens was getting terrible mileage. I went through it: Seafoam, plugs, wires, fuel filter, air filter, PCV valve, O2 sensor and cleaned the MAF & TB. Still got awful mileage. Turned out, had a small exhaust leak. Fixed it, MPG's shot way up.
Click to expand...

Where was the exhaust leaking/how did you find it?

I feel like that may be my problem, it sounds like air is escaping from somewhere
 
Mine was leaking from the muffler and believe it or not, the rear O2 sensor. I replaced the little gasket on the rear O2 sensor and the muffler, did the trick.
 
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PitbullRescuer said:
Mime was leaking from the muffler and believe it or not, the rear O2 sensor. I replaced the little gasket on the rear O2 sensor and the muffler, did the trick.
Click to expand...

I had the exact thing with mine last weekend fixed. Hasn't seemed to make a MPG difference so far.
 
Buy a manual???

34" tires, TRD/LC lift, stock engine, intake, and exhaust, 5-speed = 17.16MPG (NOT ACCOUNTING FOR OFF SPEEDO/ODO) and included city, highway, and two short days of wheeling, often in 4Lo.

For reference, my speedo calibrated to GPS shows 100km/hr at 92 km indicated. So every hour or 100km I'm doing 8 km further then the ODO shows. Don't want to calculate that out but I'm getting 18-19MPG. Before lift I got 24 on a few occasions but averaged around 20-22.

I know I'm of no help here, but I'm shocked at how some auto's get horrible mileage. I do drive slow, but figure those complaining must not be ragging on their engines either.
 
I would call myself a conservative driver. Tend to keep it under 70 and don't punch it taking off from a stop.

I used stp fuel injector cleaner today at about a quarter tank. I will most likely fill up tomorrow before heading to wyoming for the weekend (250 miles round trip). Hoping to se better mileage and if not going to do a full tune up next week.
 
16 mpg on the highway still seems a bit low. With my lift and little larger tires I was getting 16 with city driving here in Denver. I get closer to 19 mpg on the highway when I'm not towing. Of course I'm also running a manual transmission too.

Definitely take a look at your air filter, replace it if it hasn't already been. Another thing to check might be your brakes to make sure they're not dragging. I think most everything else has been suggested..

Good luck!
 
I haven't changed the air filter but will check it today and do so if needed. I replaced my brake pads and rotors the day after I bought it and no longer have the shaking when I brake.
 
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