Less than stellar gas mileage.

[vortex2450]

Hey guys,

I've noticed that my mileage has been lacking as of the past month or so, I recently pumped 3.97 gallons in moving the needle up two marks to the 3/8 mark, I've only driven 67 miles and the needle is back on the "E" mark and the light is back on.

67/4 = 16.75 mpg. :|

I drove highway miles 100% of the time, I never let the rpm's over 3k and engine brake into every stop light and try to avoid full stops as best I can.

I ran for KOEO and KOER codes and none popped up.
I run 89 octane.
The alignment was just done.
Just replaced the timing belt tensioner and timed everything up the the 3.0 marks as usual.


I do let the car warm up about 5 minutes on mornings colder than 50 degree before I drive but I don't see how I can be sucking up so much gas this way.

I was under the impression that leaving the car in gear while coasting into a stoplight saves gas but maybe the injectors are still firing?

Also, the car has a 93' Cobra MAF on it, I tried to swap this out for a stocker but it run like total crap. There appears to be no LPM installed.

Any common areas for loss of efficiency I should pay more attention too?

Thanks,
josh

 

[AREA 91]

That's about what I get around town if I can keep my foot out of it.
You should get near 30mpg on the highway.

When was your last mantainance performed?
Air and fuel filters changed?
Coolant temp and T stat?

 

[itwonder]

Try a tank of 92 octane. And measure mileage by starting with a full tank, resetting the trip odometer, driving, refilling to full, and dividing the gallons used into miles driven on the trip odometer - too much variability in trying to estimate based on gas gauge readings.

 

[JRA2000TL]

I agree with the previous poster. Our fuel gauges aren't the most accurate. Only way to be sure is the full tank and trip meter.

 

[jelloslug]

According to my MPG meter (which is very accurate) get about 16 MPG just with city driving.

 

[JRA2000TL]

According to my MPG meter (which is very accurate) get about 16 MPG just with city driving.

Really? I thought Gen I's got better gas mileage. I'd planned on DDing my 89 because my 4Runner sucks on MPG's, like 18 MPG. If that's the case, I might as well drive the SUV. It's not as fun to drive though. I probably get worse MPG in the SHO because I can't keep my foot out of it.

 

[jelloslug]

Really? I thought Gen I's got better gas mileage. I'd planned on DDing my 89 because my 4Runner sucks on MPG's, like 18 MPG. If that's the case, I might as well drive the SUV. It's not as fun to drive though. I probably get worse MPG in the SHO because I can't keep my foot out of it.

I can make it get 20 city but that's not very fun. And this is pure city drive with stop and go traffic. Absolutely no highway driving at all.

 

[rbruso]

I'm getting 18-ish in stop&go. It looks like I might have a slight uptick after replacing the original (220K mile) coolant temp sender but it's too early to have definitive numbers.

How long since you replaced O2 sensors? If they're over 80K you should consider new ones. I can't remember where (might have been the Probst book) but there was a chart comparing new and aged O2 sensor response curves.

With clean plugs, good wires, good sensors and a clean air filter I'd expect around 18 city and 25+ highway, at least driving the way I do

If you leave the car in gear coasting down the injectors should be shutting down, until you get to the magic tip-over point where fuel is required to keep the engine above a minimum RPM.

And if you're going to measure from full to full, the best results come from stopping when the auto-shutoff clicks. Don't top off. And the ultra **** out there will point out that you should use the same pump at the same station to ensure the tank is at the same level when you're running comparison tests.

 

[vortex2450]

That's about what I get around town if I can keep my foot out of it.
You should get near 30mpg on the highway.

When was your last mantainance performed?
Air and fuel filters changed?
Coolant temp and T stat?

Air and fuel filters were both changed about 10k miles ago.
I constantly maintain this car, the only "maintenance" items still on the table for me are the cam seals. 60k was done @ 120k by PO of engine, currently sitting @ 160k on engine.

Coolant temp sits where it should; on the bottom leg of the "M: when cruising and it raises up the the "O" in city driving. I cleaned the sensor up when I swapped the engine in, I have an Autometer gauge which I have been meaning to hook up as well.

I'm getting 18-ish in stop&go. It looks like I might have a slight uptick after replacing the original (220K mile) coolant temp sender but it's too early to have definitive numbers.

How long since you replaced O2 sensors? If they're over 80K you should consider new ones. I can't remember where (might have been the Probst book) but there was a chart comparing new and aged O2 sensor response curves.

With clean plugs, good wires, good sensors and a clean air filter I'd expect around 18 city and 25+ highway, at least driving the way I do

If you leave the car in gear coasting down the injectors should be shutting down, until you get to the magic tip-over point where fuel is required to keep the engine above a minimum RPM.

And if you're going to measure from full to full, the best results come from stopping when the auto-shutoff clicks. Don't top off. And the ultra **** out there will point out that you should use the same pump at the same station to ensure the tank is at the same level when you're running comparison tests.

02 Sensors replaced a little more than 10k ago as well. Bosch sensors.

And is this "fuel cut on point" somewhere around idle? I usually put the car in neutral once I've reached a speed where the rpms are around 1200.

I can't fill the tank all the way up. Another thing I forgot the mention was the fuel pump seal leaks ever so slightly and I can smell gas whenever I fill up.

I'm thinking I will run this next tank dry, have exactly 2 gallons metered out on a gas can in the trunk, then go the nearest station and pump exactly another 8. 10 makes for an easy divider. Right?

Does the fact that I am riding on 235 tires versus 215 tires play a role as well? I would assume more rolling resistance would lead to a loss in efficiency as well.


-Josh

 

[shobote]

Sticking caliper can adversely affect mpg. Easy way to check woithout jacking up all corners; after a highwy run, where the brakes are not used for a while, pull over and feel the wheels and if one of them is hot, that caliper is sticking.

 

[overthehill]

I would second the recommendation of using 91 or better octane fuel. Makes a difference as it allows more timing advance which usually always improves fuel economy.

I am fortunate that in the area where I live (Virginia) many places have gasoline without ethanol. I can see a 10% improvement in mileage when I use non-ethanol. I check my mileage often and find I get 30-32 mpg on the highway and low 20's around town.

I've also found that I don't put my foot in it as often as I used to do. Must be getting old or maybe I'm trying to make this old car last a few more years.

 

[AREA 91]

If you have a fuel leak, you need to address that ASAP!!!
You won't care about mpg's if your dead!

 

[220ksho]

Does the fact that I am riding on 235 tires versus 215 tires play a role as well? I would assume more rolling resistance would lead to a loss in efficiency as well.

Yes, but more importantly, if your speedo is off because of the overall tire diameter, your distance traveled is inaccurate.

 

[itwonder]

Also check the fuel tank venting system.

 

[intimdatr]

Yes, but more importantly, if your speedo is off because of the overall tire diameter, your distance traveled is inaccurate.

That number is in reference to width, not hight.

 

[Cl-Slick]

You could have bad catalytic converters, mine have gone bad. The car has no power and I only got 170 miles out of a full tank of 93 octane. I'm having them removed come payday.

 

[kevinspann]

That number is in reference to width, not hight.

But the aspect ratio also plays an important role too.

A 235/60/16 would be taller than a 215/60/16, for example.

 

[kevinspann]

You could have bad catalytic converters, mine have gone bad. The car has no power and I only got 170 miles out of a full tank of 93 octane. I'm having them removed come payday.

He's catless.

 

[SHOtime2511]

measure mileage by starting with a full tank, resetting the trip odometer, driving, refilling to full, and dividing the gallons used into miles driven on the trip odometer - too much variability in trying to estimate based on gas gauge readings.

^This.

 

[intimdatr]

But the aspect ratio also plays an important role too.

A 235/60/16 would be taller than a 215/60/16, for example.

By maybe a few millimeters?