fuel economy

[cld783]

Pfft, I'm running 1990 LTC O2 sensors and currently rocking 19mpg all city on my Frankenstein. If the OP does all city driving, some lower gears could actually help in the economy department as well. A good tune will do wonders as well, should be the first mod of ANY car.

they make a huge difference if faulty or aged. if you knew anything about o2 sensors and how the computer uses them for adaptive strategy you'd know.

[SVT98t]

I actually dont run o2 sensors. Mine are unplugged. I have, a 93 Mercury Grand Marquis. And it looks just like the one in my sig. I go green. lol.
I'm not sure if the driveshafts would swap right over. I'm pretty sure the output shafts are the same, just not sure about the length of the drive shaft itself.
If anyone has an AODE or 4R70W, I would highly recommend doing the J-mod. I didn't do the full J-mod on mine; I just drilled out the separator plate to spec. No accumilator springs were removed. And it still has a firm, authoritive shift.
And I use E3 spark plugs.

-ryan s.

[thewishkah]

180miles on 16.8 gallons. I just replaced my fuel filter in hopes that it may help a bit but who knows?! When I tilted the old one it looked like coffee grinds coming out of it so I assume that it was pretty dirty, I don't know the last time it was changed as I only got the car in January. Since then I have replaced the spark plugs with motorcraft copper, the air filter, checked the pcv valve(good), cleaned the maf and throttle body plenum, and made sure its always properly inflated. And I have kept up with the usual oil changes. Also I do not see much of a difference even when I baby the gas pedal for a whole tank, If I drive with a slow and even acceleration I get maybe 200 to the tank tops. Any other ideas?

[1980c10]

Are you sure your speedo is reading correctly? And are you calculating correctly? Fill it up, drive it, fill it back up. Then how many miles you went divided by how many gallons it took to fill it back up? If your car is actually only getting 11 mpg there is something wrong. If you take lots of short trips let the car idle and warm up to operating temp before you drive.

[thewishkah]

I am sure I calculated correctly. I filled it completely then I drove till the low fuel light came on. I filled it which took 16.8 gallons and I had only driven 180 miles. This is the average. I have to fill it once a week and its pretty much right on the money every time. I have done fuel filter, air filter, plugs, this past week i did coolant change and flush, I have cleaned the tb, and maf and still not seeing a noticeable increase at all. It seems as though the gas mileage got worse when I tried to baby the pedal for a full tank I only managed 165 miles that way. I do not want to throw money at it with out first really researching the issue. I have hooked my scanner up to the car which gives me a full read out of data but I'm not sure what all of it means. There are no codes and no dummy lights on either. Any ideas would be great, Thanks.

[1980c10]

Put more air in your tires. Inflate them to max recomended pressure on the sidewall, prolly somewhere in the 45psi range. Also since you do alot of stop and go and short distances if you have acces to plugins where you park, you could install a block heater that way the engine will be warm as soon as you start it. Driving on a cold engine kills milage.

[SVT98t]

Unfortunately, these are highway cruisers. It takes alot of power/gas to make these go. My only recommendation, as bad as it seems, would be to downsize.
Unless you need the cargo space, seating, safety; then you might want to look elsewhere.
4.10 gears might help your cause.

-ryan s.

[johnunit]

10mpg is pretty brutal, and that's about what thewishkah is getting. I top that in the city with 2.73 gears, a heavy foot, and a carburetor in my vic, often with passengers. I'd suspect brakes or bearings dragging or something if the engine is ok. Clogged cat maybe? Something is seriously wrong unless you're doing a huge amount of idling.

[thewishkah]

Well I did a seafoam treatment today, not sure how much it will help if any but it did make A LOT of smoke and crap come out of the exhaust. I also took pictures of the data stream on my obdII scanner maybe that will help someone identify my problem?

[zoomie]

yup i understand that i get like 12 mpg at the moment...grrr i need to fix the vac leaks fo sho!

[thewishkah]

[thewishkah]

Im not really sure what to make of it. If anyone knows please chime in.

[thewishkah]

here's the video of the after seafoam effect. http://youtu.be/w9-oAUE-Lu8

[sly]

as far as the smoking after the seafoam... run it a while... it should clear up. They always look like a mosquito truck while the seafoam does it's dirty work. You don't need to drive it around... just run it a while.

if it doesn't clear up... or gets worse... then the valve seals are probably shot and now unclogged and it's burning oil.

[MattsLincoln]

I am sure I calculated correctly. I filled it completely then I drove till the low fuel light came on. I filled it which took 16.8 gallons and I had only driven 180 miles. This is the average. I have to fill it once a week and its pretty much right on the money every time. I have done fuel filter, air filter, plugs, this past week i did coolant change and flush, I have cleaned the tb, and maf and still not seeing a noticeable increase at all. It seems as though the gas mileage got worse when I tried to baby the pedal for a full tank I only managed 165 miles that way. I do not want to throw money at it with out first really researching the issue. I have hooked my scanner up to the car which gives me a full read out of data but I'm not sure what all of it means. There are no codes and no dummy lights on either. Any ideas would be great, Thanks.

right now my 1983 GM CFI gets 12MPG in the city and about 21 on the hwy.