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500 mile trip to school. trying to maximize efficiency

toates89

toates89

NAXJA Forum User
Location
suffolk
Sorry I know the topic is beat to death but i just figure that i shouldnt have to go through two tanks of gas for the trip and its really hard on my wallet about 100 bones each way isnt easy for a student.

The rig:
89 4.0
5 speed
31's
3 inch lift
no armor
160k compression good
3.07 gears
running about 1900 rpm at 65mph
new map sensor
Minor crack in exhaust mani
new 02 sensor
The temp doesnt get ever get close to 210 changed the thermostat with i believe 195 a year ago. temp gets tot he line between 210 and 0 and stays there.
aem dry flow intake
the exhaust has been changed since but not sure how long ago
new wires dist cap and rotor and plugs(going to clean them tmrw as it used to run rich)
runs good nice power nice steady idle(900 a little high i think)
Egr non functional
no intake manifold vacuum leaks(no leaks that i can find)
breaks not dragging as far as i know
needs an alignment
tires at 32 psi


so it takes me 32 gallons to go 500 miles(not on odometer but googled map directions) so about 15mpg figured with the 5speed and low rpms i should be doing a bit better.

i also travel through the adirondaks and i am in between 5 and 4th gear because of the steep inclines. prob not helping the average.


sry again to do this to everyone. just wanted to see if my situation stood out at all

i think apart of my jeep bug is making everything work to the best of its ability
 
i heard i can check everything as far as fuel managment with a multimeter. what systems should i check for proper operation?
 
toates89 said:
i heard i can check everything as far as fuel managment with a multimeter. what systems should i check for proper operation?
Click to expand...

Check your AIC and TPS. Might solve your high idle problem. Get a can of throttle body cleaner and clean the whole throttle body out. Make sure to get in the side port where the AIC mounts with some q tips or something.

Lock out hubs would drastically help your mileage... but they're pricey. Good for 1-2 mph I heard, but I've never had a vehicle with lock out hubs.

Take out any extra weight...

Tail gate a semi...

99+ intake swap...

Port polish and gasket match head...

Full exhaust...

Full synthetic in all your fluids...

Install a vac gauge and change your driving habits accordingly...

And last but not least, buy a Honda...

Mileage is a tricky animal to catch. I try and improve where I can, but it seems like my mileage is dependant on where I have to drive... Like to work at a ski resort, uphill the entire way there...oh well, what can you do?
 
nochance9 said:
Check your AIC and TPS. Might solve your high idle problem. Get a can of throttle body cleaner and clean the whole throttle body out. Make sure to get in the side port where the AIC mounts with some q tips or something.

Lock out hubs would drastically help your mileage... but they're pricey. Good for 1-2 mph I heard, but I've never had a vehicle with lock out hubs.

Take out any extra weight...

Tail gate a semi...

99+ intake swap...

Port polish and basket match head...

Full synthetic in all your fluids...

Install a vac gauge and change your driving habits accordingly...

And last but not least, buy a Honda...

Mileage is a tricky animal to catch. I try and improve where I can, but it seems like my mileage is dependant on where I have to drive... Like to work at a ski resort, uphill the entire way there...oh well, what can you do?
Click to expand...

i cleaned my aic(with carb cleaner. whoops) and cleaned the port. maybe not spotless but cleaned it decently.

little nervous about cleaning the tps. i heard that they cant be cleaned and once moved need to be recalibrated
 
toates89 said:
31's
3 inch lift
3.07 gears
Click to expand...

Well, there's your problem. Seriously, that right there (meaning worse aerodynamics courtesy of the lift coupled with stock gears turning larger tyres) is likely your biggest hit. That crack in the manifold probably isn't helping any either, as may be the non-functional EGR valve (though to a lesser extent). Have you corrected for speedo error with the oversized tyres?

Honestly, though, 500 miles divided by 32 gallons is 15.625mpg. Not knowing your driving style or the mix of city/highway driving involved here, that doesn't sound too off the mark for an average.
 
casm said:
Well, there's your problem. Seriously, that right there (meaning worse aerodynamics courtesy of the lift coupled with stock gears turning larger tyres) is likely your biggest hit. That crack in the manifold likely isn't helping any either, as may be the non-functional EGR valve (though to a lesser extent). Have you corrected for speedo error with the oversized tyres?

Honestly, though, 500 miles divided by 32 gallons is 15.625mpg. Not knowing your driving style or the mix of city/highway driving involved here, that doesn't sound too off the mark for an average.
Click to expand...

i averaged about the same mileage prior to lift and tires. and i may be wrong but i thought larger tires hurt taking off from a stop but can help on the highway. its a 500 mile trip on basically one road(nys thurway for 430 miles)

miles of trip not based of odometer and is based of gps
 
the_weirdo said:
Drive at 55mph.
Click to expand...

I hear that. when i am on the island i try to keep it at 55. but on the thurway where the limit is 65 its tough with all the trucks. plus at 55 its real hard to keep it in 5th gear

would you say i would get better mpg doing 55 in 4th gear or 65 in 5th?
 
Think of your MPG in relation to the position of the throttle plate.

With 3.07s on those 31s you are out of the "power band" of the engine and have to use more throttle to maintain speeds. You would be better off to stay out of 5th and keep the RPMs up higher with less throttle.

Slow down to 55 as suggested already. Increase the pressure in your tires just for the trip, perhaps up around 36 psi.

Any exhaust leak upstream of the o2 sensor will cause an indicated "lean condition" to the ECU--the ECU increases the duration of the injector firing pulse to correct the lean condition thereby wasting fuel.

Fix your idle speed--700 to 750 RPM after 20 minutes of engine operation. Your high idle could be due to a number of things. Intake leak will lean the mixture and that gives you a high idle. Uncle Bob may have adjusted the "idle screw" that doesn't exist on the throttle body. There is a 3/32 Allen screw on the throttle body that has one and only one purpose--it is there and adjusted so the STEEL throttle plate doesn't slam fully closed and damage the ALLOY throttle body. Uncle Bob can't understand that and likes to tinker with it all the time. If you think Uncle Bob may have messed with it you can undo the damage easily. Remove the intake tube from the throttle body. Back off the 3/32 Allen screw until it no longer effects the throttle plate--so that the throttle plate is fully closed. Slowly turn the 3/32 Allen screw in while observing the throttle plate--AT THE FIRST PERCEPTIBLE MOVEMENT OF THE THROTTLE PLATE STOP TURNING THE SCREW. Put the intake tube back on you are done. Now, adjust the TPS as it will likely be a little out of adjustment.

The IAC--Idle Air Controller--is a stepper motor that has a pintle that extends and retracts on command from the ECU. When Uncle Bob screws with the screw the IAC can't do its job, the ECU gets mad and starts changing things because it wants things the way it wants them to be and after a little while you have a mess.

Now, Winter blend fuel will rob you of 10 percent of your MPG. If you have E10 fuel--ethanol--that will rob you of another 10 percent of your MPG.
 
Last edited:
joe_peters said:
Think of your MPG in relation to the position of the throttle plate.

With 3.07s on those 31s you are out of the "power band" of the engine and have to use more throttle to maintain speeds. You would be better off to stay out of 5th and keep the RPMs up higher with less throttle.

Slow down to 55 as suggested already. Increase the pressure in your tires just for the trip, perhaps up around 36 psi.

Any exhaust leak upstream of the o2 sensor will cause an indicated "lean condition" to the ECU--the ECU increases the duration of the injector firing pulse to correct the lean condition thereby wasting fuel.

Fix your idle speed--700 to 750 RPM after 20 minutes of engine operation. Your high idle could be due to a number of things. Intake leak will lean the mixture and that gives you a high idle. Uncle Bob may have adjusted the "idle screw" that doesn't exist on the throttle body. There is a 3/32 Allen screw on the throttle body that has one and only one purpose--it is there and adjusted so the STEEL throttle plate doesn't slam fully closed and damage the ALLOY throttle body. Uncle Bob can't understand that and likes to tinker with it all the time. If you think Uncle Bob may have messed with it you can undo the damage easily. Remove the intake tube from the throttle body. Back off the 3/32 Allen screw until it no longer effects the throttle plate--so that the throttle plate is fully closed. Slowly turn the 3/32 Allen screw in while observing the throttle plate--AT THE FIRST PERCEPTIBLE MOVEMENT OF THE THROTTLE PLATE STOP TURNING THE SCREW. Put the intake tube back on you are done. Now, adjust the TPS as it will likely be a little out of adjustment.

The IAC--Idle Air Controller--is a stepper motor that has a pintle that extends and retracts on command from the ECU. When Uncle Bob screws with the screw the IAC can't do its job, the ECU gets mad and starts changing things because it wants things the way it wants them to be and after a little while you have a mess.

Now, Winter blend fuel will rob you of 10 percent of your MPG. If you have E10 fuel--ethanol--that will rob you of another 10 percent of your MPG.
Click to expand...

WELL I DID CLEAN THE IAC

I SPRAYED EVERYWHERE WITH CARB CLEANER AND DIDNT NOTICE ANY JUMP IN THE RPMS. I TIGHTENED ALL INTAKE BOLTS AND SPRAYED THERE ALSO AND AGAIN NO JUMP.

DOES THE TPS PLAY A FACTOR IN IDLE RPMS?

I DOUBT THE PO FUDGED WITH THE SCREW AS THERE WASNT A TACH IN THERE UNTIL LAST WEEK SO I COULDNT IMAGINE ANYONE TOUCHING SOMETHING LIKE THAT WITH OUT A TACH

STILL AT A LOSE WITH THE IDLE
 
toates89 said:
ON THE e10 NOTE I ROUTED MY TRIP SO THAT I WILL PITSTOP AT ETHANOL FREE GAS STATIONS THAT I FOUND ON PUREGAS.COM
Click to expand...

EXCELLENT!

E10 is mandatory in OR. They did, as of January 2010, allow a limited number of stations to sell PREMIUM ONLY non-ethanol fuel--$$$$$.
 
toates89 said:
WELL I DID CLEAN THE IAC

Yep, saw that. However, Uncle Bob--he is quite a character, he has been the previous owner of a lot of vehicles, he has worked in service stations, he is the always-helpful neighbor lending a hand, and sadly he has worked in way too many "professional" garages. Don't a**ume, adjust it like I posted above.

I SPRAYED EVERYWHERE WITH CARB CLEANER AND DIDNT NOTICE ANY JUMP IN THE RPMS. I TIGHTENED ALL INTAKE BOLTS AND SPRAYED THERE ALSO AND AGAIN NO JUMP.

Yeah, that trick doesn't always work. First, it could be that 3/32 Allen screw holding the throttle plate open enough that the IAC can't control the idle no matter what the ECU tells it to do. Adjust it like I posted above.

DOES THE TPS PLAY A FACTOR IN IDLE RPMS?

Yes--sort of. The TPS reports the throttle position to the ECU. The ECU collects data from all of the sensors and, depending on pre-programmed parameters, adjusts the idle speed. Every time a sensor goes bad the ECU gets FALSE data. The Renix ECU is very limited, it doesn't store codes and it doesn't throw a CEL--it is going to try and get things sorted out but when the data it receives is bogus things turn ugly pretty quick.

Ok. Lets PRETEND the 3/32 Allen screw is not set correctly. Lets say it is backed too far out--worst case the throttle plate will damage the throttle body bore, that damage will allow air to bypass the throttle plate and you will have a high idle. Lets say it is turned too far in--that means the throttle plate isn't closed and too much air is bypassing and causing a high idle. Alright, well what else is going to be wonky? The ECU is receiving data from all the sensors and sending commands to the IAC--however, the air/fuel mixture is screwy because too much air is getting in, the TPS is reading wrong because the throttle plate is damaged or open, the o2 sensor, MAT, MAP, CTS are all screaming bloody murder along with the crank sensor and synch (cam) sensor.

I DOUBT THE PO FUDGED WITH THE SCREW AS THERE WASNT A TACH IN THERE UNTIL LAST WEEK SO I COULDNT IMAGINE ANYONE TOUCHING SOMETHING LIKE THAT WITH OUT A TACH

Uncle Bob is one wily son-of-a-gun! He has been known to actually buy/borrow a tach and use it on vehicles. Even worse, Uncle Bob's brother, Uncle Fudd, well he just likes to adjust it by "ear". Don't A**ume, adjust it.

STILL AT A LOSE WITH THE IDLE

Follow the steps, adjust the screw, adjust the TPS, report up the idle speed you achieve.
Click to expand...
 
Well i never got around to tracking down the idle issue prior to leaving for school(but i did bring my tools cept in buffalo its about 5* out give or take and that means i am no doing anyting out side)

But i drove it like a granny on sedatives. i kept the spedo at 55 which means about 60mph with no passing and going through the bronx and everything i was able to get 210 miles(so about 231 after tire correction) before i decided to fill up with a 1/4 of a tank left. at the pump i was able to squeeze 11 gallons so i was at about 21 mpg(shoulda seen me smiling) filled her up and got back on the road.

the route i had to take because my mom killed my ezpass didnt allow me to stop at E10 free places

but the second tank i go the worst mileage i think i got 150 miles off of 12 gallons. i know it was significantly worse. maybe the combo between the gas from the different station plus it got hillier(which means the gear ratio i am running is really killing me) and maybe i wasnt as easy as the first tank.


all in all i am very happy to know if i at least try i can squeeze 20mpg. not bad for an 89 with 3" and 31"s
 
no way your gonna get 20 MPG's!

Anyways, isnt carb cleaner VERY BAD for electronic sensors? I just took apart the throttle body on my 94 for a through cleaning, and was reading that I should only clean it with only throttle body cleaner designated safe for sensors. I read carb cleaner could also damage downstream sensors like O2.
 
PhotographerMike said:
With your gears (3.07) I don't think I'd ever use 5th gear, especially on any kind of hill. Did you check your actual speed with a GPS? Actual 55mph with 32's you're barely out of idle range.

Mike
Click to expand...

yeah i gave up on going from 4th up to 5th down hill to a an overall slower speed in 4th

I am pretty sure i got 20mpgs on the last trip. i filled then drove 230 miles and refilled and it only took 10.7 gallons so even if it was 1.3 gallons incorrect i still would have gotten 19mpgs

55mph does wonders
 
joe_peters said:
EXCELLENT!

E10 is mandatory in OR. They did, as of January 2010, allow a limited number of stations to sell PREMIUM ONLY non-ethanol fuel--$$$$$.
Click to expand...

from the 1990 fsm regarding the use of 90% gasoline to 10% ethanol. "CAUTION: EXCLUSIVE USE OF THESE FUEL BLENDS IS NOT RECOMMENDED. Vehicle test results have shown that significant fuel system corrosion can result when they are used exclusively."

and in Massachusetts you can find ethanol free gas.
 
After I lifted (3" and 31s) I got about 16 on the road. I re-geared to 4.10s. When I have my stock aluminum wheels and street tires (10bs lighter than soft-8s and MTs) I can get between 20 and 21 if I keep it around 60mph on summer-mix gas. I can also cruise all day long up any hill in WV at 70mph in 5th gear.
 
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