Very Low MPG

[glwagonman]

Today i figured out how many miles to the gallon i was getting and i got a very low 12 that's as much as my friends silverado gets so i was just wondering what could be casing it to be soo low?

i have recently put in a new air and fuel filter and new plugs

Thanks in advance

[idosubaru]

this is a tough one, very open ended without much information.

what motor - EA82?

what kind of driving are you doing, what transmission?how's the acceleration and performance, everything is normal, no check engine lights?

 

plugs wires, cap, and rotor.

air filter, fuel filter, O2 sensor, timing set properly?

 

brakes could be dragging..not seized or bad in any way, just dragging. i've seen vehicles get a few mpg better after a brake job eventhough everything was working fine. grease the pins properly - with brake specific grease.

[glwagonman]

yeah sorry i completely forgot to say its a 1987 gl wagon auto trans

i just got new spark plug wires and a new rotor it has a dead spot in the gas pedal and not to much highway driving more city

[ScottG]

A couple of other things to check:

 

1. TPS - this could be the cause of the 'dead spot' in acceleration. Adjust to spec.

 

2. PCV Valve - been known to cause horrendous drivability problems when plugged up. Get a new one from Subaru. Aftermarket ones are chancy. Should be changed as part of your regular tune-up, along w/ plugs, etc. Check the big vac lines to see if they've gotten plugged up

 

3. Vacuum leaks - have you checked all your vac lines. a vac leak will kill your MPG. Replace cracked rubber vac lines. If you're not sure, $7 worth of rubber tubing from NAPA or wherever, will pretty much replace all your lines.

 

4. tires - what kind of pressure are you carrying? Put at leat 30 psi in each tire.

 

5. oil - what weight oil are you using? stuff like 20w50 in New England winters will kil your MPG

 

6. thermostat - are you running at least a 180 degree thermostst? Is it opening properly? Do you have enough heat in the wagon? The temp must be high enough to shut down the fuel enrichening circuit...otherwise, crappy MPG

 

When did your MPG start to fall?....was it gradual, over 3 or 4 tanks of gas?....or was it very sudden & dramatic, like a drop from 25 MPG to 12 lterally overnight?.......Did this occur after you changed plugs, etc?

[GeneralDisorder]

Probably a lot of factors at play.

 

First - please describe the complete formula and procedure you use to calculate your mileage.

 

GD

[glwagonman]

i run it to almost empty go to the gas station and see how much goes in to it so i know how many gallons it used and then look at the trip counter thing theremight be a better way but thats the way i know of

[GeneralDisorder]

Carb or SPFI?

 

Check your tire pressure first, and verify your speedo isn't slow. Have someone pace you with another rig and make sure the speedo and trip are reading correctly.

 

GD

[glwagonman]

1.My manual says i dont have a TP sensor

2.PCV valve looking in to it

3.My friends buddy said there was a vacuum leak but i have looked for cracked tubes and i cant seem to find it

4.tries are fine

5. i have 10w30 in it

6.im not to sure about the thermostat i think it is the original

and it was a it slowly failed i when i first got the car a year and a half ago it got 27 MPG highway

[screwbaru2]

i run it to almost empty go to the gas station and see how much goes in to it so i know how many gallons it used and then look at the trip counter thing theremight be a better way but thats the way i know of

 

Try filling the tank. Zero out the tripodmeter. Drive till less than 1/4 tank. Refill tank, record gallons and miles on tripodmeter. divide the miles by the gallons. that's your mpg.

[glwagonman]

it is carbed

[ScottG]

If you're carbed, & doing a lot of around town driving in cold weather - well, that's a formula for crummy MPG....but there is hope!

 

1. Make sure the choke is opening. There should be some electric or vacuum mechanism to open it...not sure which carb you have.

 

2. If you can adjust the choke, make sure it opens as soon as the power is tractable (able to deliver fairly usable power w/o choke)

 

3. I have a sneaky suspicion that your choke is the culprit - that would account for the 'dead spot' in your aceleration.

 

4. There may be some other problem w/ the carb: jets, float level, crud that managed to get through your fuel filter, etc. Check the float bowl to see that float is set correctly and that no crud is plugging things up.

[Stevethefolkie]

it is carbed

betcha your choke is stuck shut or partially shut ... when you've driven it a bit pop the lid off the air cleaner - if the choke isn't wide open figure out why - it may just be gummed up, the electrical connector to the automatic choke may have fallen off or it might have worn out -

[glwagonman]

ok im going to look at the choke

[glwagonman]

i took her on a drive tonight and when i got back i looked at the choke and it was straight up so i dont think that is my problem

[audio_file]

ya know, i've never done better than @20mpg w my 87 wagon, i'm very interested to see what your problem ends up being. my wagon is also carbed, ea82, 3AT, w full tune-up 3500 miles ago. is yours 4wd?

original fuel pumps?

seafoam lately?

complete emissions setup still or "de-smogged"? (not to judge, just for info)

 

chris

[one eye]

I know you guys are in a deep conversation with trying to find out what the deal is, but a Weber would clear this up no problem. I would highly recomend a Weber.

Jeff

[GeneralDisorder]

Ok - so it's carbed.

 

Now we need to know if it's a feedback carb or not.

 

Do you have an Oxygen sensor right in front of the catalytic converter? Should be a single wire dingus screwed into the "crotch" of the y-pipe.

 

GD

[audio_file]

I know you guys are in a deep conversation with trying to find out what the deal is, but a Weber would clear this up no problem. I would highly recomend a Weber.

Jeff

 

you should be a weber sales rep

[spokanesoob]

weber fixed my gas mileage just thought i would throw that in

check to see if your leaking any gas anywhere that could throw your mileage off

spokanesoob

[pyro926]

weber fixed my gas mileage just thought i would throw that in

check to see if your leaking any gas anywhere that could throw your mileage off

spokanesoob

My weber is giving me crappy milage. It also has the dead spot at wide open throttle. I wonder if my choke it acting up too......

 

 

oh, and the gas leak would be real easy to find. just start a small fire in the street and drive slowly over it.

[audio_file]

oh, and the gas leak would be real easy to find. just start a small fire in the street and drive slowly over it.

 

i guess we don't need an explanation for your screen name now . . .

gas leaks are pretty easy to find, my constant sinus headache from the gas smell on my wagon led me to repair/replace some hoses around the external fuel pump that had ballooned up and were leaking . . . now my garage and house smell a lot better too . . .

my .02 would be that you have a vacuum problem- print out the vacuum diagram thats here on the usmb and start checking hoses (so much fun :-\ )

oh and seafoam, 2 bottles of seafoam, seriously

[glwagonman]

Ok - so it's carbed.

 

Now we need to know if it's a feedback carb or not.

 

Do you have an Oxygen sensor right in front of the catalytic converter? Should be a single wire dingus screwed into the "crotch" of the y-pipe.

 

GD

nope no oxygen sensor

[glwagonman]

ya know, i've never done better than @20mpg w my 87 wagon, i'm very interested to see what your problem ends up being. my wagon is also carbed, ea82, 3AT, w full tune-up 3500 miles ago. is yours 4wd?

original fuel pumps?

seafoam lately?

complete emissions setup still or "de-smogged"? (not to judge, just for info)

 

chris

mine is 4wd and it has 61,000 miles on it i think almost evrything in the car (besides the stuff i have put in it)is stock not really sure what seafoam is

[Rooinater]

my weber gets doesn't get great gas mileage, but i'm sure it's jetting or the throttle plate is going bad...

 

as for checking for vacuum leaks, try spraying carb cleaner on around the hose connections or suspected leak, if engine stumbles it's a vacuum leak.

[GeneralDisorder]

nope no oxygen sensor

 

Now we are getting somewhere.

 

1. Get some brake cleaner or carb cleaner. Spray all around the carb - at the base, the throttle shafts, etc. If you hear the engine change pitch (RPM increase) then you have a leak near the location of the spray. Fix any leaks you find. Trace as much of the vacuum line system as you can.

 

2. Look down the carb throat while revving the engine. Use a flashlight if you need to. Pay special attention to the spray pattern of the primary and secondary jets. You should see a fairly even spray pattern. If it's dribbling, or not spraying evenly this will need to be addressed with a carb tear down. Make sure the accelerator pump isn't leaking and is pumping fuel each time you rotate the throttle.

 

3. Check the operation of the distributor vacuum advance pot. Hook a section of vacuum line to the pot and suck on it. It should move the advance plate inside the disty and it should HOLD it there if you pinch the line while sucking on it. If it bleeds down faster than 10 seconds or so, the diaphragm is shot.

 

4. Verify the timing is set to about 8 degree's BTDC. You can use a timing light, but you can also just set it static when the engine isn't running. Verify TDC on #1 using a drinking straw. When the timing marks come up on the flywheel, both valves are closed (you'll feel air escaping with your finger), and the straw says it's at TDC, align the timing mark with 8 degrees BTDC, and then move the distributor till it's pointing directly at the #1 plug wire tower. This will be close enough to 8 degrees if you are careful. I'm usually within a half of a degree if not dead nuts on 8.

 

5. Check for slop in the timing belts. They get loose as they stretch and allow the timing to jump all over the place. They should be adjusted if you don't remember the last time it was done. Or just replaced if you don't remember the last time that was done either. Make sure the crank sprockets are on in the correct order (the one with the groove in the back goes next to the crank seal).

 

Beyond that how is the idle speed? Overall running of the engine? Does it miss and stumble? Does it accelerate smoothly with apparent power? Are there dead spots in the throttle? If so where?

 

The amount of mileage loss you are describing could only be attributed to a number of problems occuring simultaneously. Start adjusting and ruling out things one by one.

 

At the end of the day you may need to rebuild that carb. I've done plenty of Hitachi's and they are no picknik to rebuild. The biggest source of problems I had when rebuilding them was problematic cheap rebuild parts. Most especially the float needles and seats. Buy the highest quality rebuild parts you can get.

 

Weber's are decent. But they can be a pain to tune at times, and they require seasonal tuning. They have a tendancy to bog out on hard cornering, or severe off-angle running unless the float is set in a posistion that is not desireable for decent mileage.

 

The far better option is SPFI - especially for you as your EA82 is already setup for it. It's basically a bolt-on and crimp some wireing. The cost is generally less than a Weber with all the performance and none of the drawbacks. It does, however, require about 150% more labor to install. A couple weekends anyway if you haven't done it before. Straight Weber swaps can be done in a day, maybe two if you have all the right stuff. Still I prefer the SPFI having run multiple vehicles with both.

 

GD