ok so i have a quick poll for everybody. what kind of miles to the gallon do you get with our cars? i have the 2.8 and i get 15 around town...and thats not getting on it. highway is still probably around 18 or so. i used to get like 18 all the time. by the way i have no cat, high flow muffler, rain shields removed from intake and maf screen removed. got 15 before i took out the maf screen though. thanks

 

with my big cam,... and driving it like I stole it....about 16 city and 26 highway.

 

I was getting around 20 city and 30 highway, but I think my fuel return line is leaking and needs to be replaced ...

 

Im roughly the same as Maverick and AM91, probably in the middle. Im running pretty rich too, need a tune.

 

so what the hell could be wrong with mine??

 

I'd replace the MAF. Let's just say that that screen was there for a reason (straightens out the air flow coming over the frequency film and blocks larger debris from clogging it). Looking at it another way, let's say that the screen in the MAF cost GM around 5 cents per unit (probably more, but let's just say this for numbers). Multiply that by hundreds of thousands of MAF sensors across thousands of cars (let's say 100K units here), and you have $5000. Would GM spend that kind of money on something that isn't absolutely necessary?

Also, when was the last time you did a tune up? Did you use Delco R42 plugs? Did you replace the O2S?

 

yeah but i got 15 before the maf mod. so take that variable out. am i running too rich?

 

i get 15 mpg all day city or highway and its driving me crazy i replacing every sensor in the car air-temp, tps IAC, O2, coolant temp, the whole ignition system, MAP and the vac lines the canister near the air filter and im still getting 15

 

maybe ya'll have leaky injectors or something.

 

ok so we are in the same boat. maybe we'all have leaky injectors. and i was just about to start swapping sensors.

 

yea im down to that now but i want some of them ford injectors everyone been talking about. but can't find any 2.9s to get them out of

 

I've had mine for about a month and a half, and my mileage is terrible! I'm getting about 11mpg flat.

Finishing a tune-up this weekend, but thus far I've changed oil/filter, air filter, properly inflated tires, and ran Sea Foam through the intake and fuel.

Today I changed my plugs, wires, distributor cap and rotor, PCV valve, and in the morning I've got an O2 sensor to put on.... then we'll see if I get any improvement. Oh, my timing is WAY off too. So I'm going to set that as well. The thing is, the car runs great! If you didn't smell how rich it runs, you wouldn't ever know that the mileage is so poor or that it was as in need of a tune-up as it was...

 

Heh trade it in for a Cavalier or Cobalt, problem solved 25-30 mpg, Worn valve train can also be a big factor the harder your engine works the more fuel it dumps trying to leg it out, Flush the motor gunk out that also leads to resistance in performance (not in the nascar way) The more smoothly it runs most likely the better mpg you get,you get the idea, um check the voltage on the injectors sometimes a short can cause the to dump mass splurges of fuel, computer components in general,Timing what else... Oh transmission filter gunked up, Oh and accessory pulleys locking up or giving resistance, And the AC being stuck on the on position. Those are all things I can think of that will drop MPG

 

Just finished that tune-up, and it feels like a whole different car! The engine is snappy and responsive, and the idle dropped and evened out at roughly 700 rpm. I barked the tires a few times unintentionally while taking it for a test drive! That's a new one. It had a vibration in 3rd and 4th gear before, and now it's completely gone. Smooth through every gear and RPM.

Time will tell, but I was only getting 150 miles per tank of gas. I'd like to see at least some improvement.

 

I hope you fixed your timing too. Shoulda fixed that first, before buying a bunch of parts.

If your timing is off, you could end up messing up all the new sensors & such, by running pig rich.

 

Huh???? if the timing is off far enough to mess up fuel burn that bad....I'm not sure that you'd even be able to get the car to move, anyway!

 

Simple......Start with the free fixes, before spending $ on parts.

 

Being that the car is new to me, everything I did is part of a basic tune-up that should be done regardless of whether the timing is off or not. And yes, I did adjust the timing back down to 10 BTDC like it should be.

Upon removing the plugs and wires, I discovered that the previous owner spray bombed the motor with the plugs still installed. I don't know how this motor was getting any spark. The ends of them were covered in thick blue paint. And a few of the plugs themselves had very heavy deposits.. a few wires had heavy corrosion and or rust on both the distributor and plug side. I really don't know how this car ran before the tune-up!

 

"...did adjust the timing back down to 10*..."

where was it? a few degrees advanced won't hurt you. In fact, it'll probably make the car a bit more "peppy" on bottom end.

 

hello, i have a 2.8 on my 86 camaro, the question that has been itching is how good is it on gas? oh and another major detail. its got a carbie. and a detail on the carbie. its only got the small throat.. the big one was bad so i had to cover it. it was getting too much air and accelerating out of control. how much could i expect? thank you!

 

The carb motors suck fuel. Best I've heard of is 18mpg. Normal for mpfi is ~23mpg. I'm getting about 26 city 32 highway, but I'm not using the stock ecm or injectors.

 

hm but that would be with both throats working.. you think it makes a difference? hopefully i wont be stuck with less than 13 or 14

 

One's a secondary that opens at higher throttle positions. Yours is stuck so you might actually see better mileage... if you don't get impatient.

 

It was about a half inch off the timing tab!

 

ahh so then i cant really accelerate... how fast do you think i can get to highway speeds? and about how many miles should i see? can i do something to boost them? i read somewhere that someone dropped their hp and got 40mpg... is that plausible? i'm a car newb.. well somwhat.. i just dont know the terms.. but i know how things work... thanks!

 

You'll still get to the same speeds, just not as quickly. Get the carb working. And clean. Don't know what your mileage will be or if it will improve, but the carb won't help you. Best way I've heard it put is a carb is like painting with a cup. Fuel injection's a brush.

Improving your mileage is as much psycological as it is mechanical. If you're an impatient driver like me you can quickly degrade your mileage by sticking your foot in it alot and constantly triggering accel enrichment. That's why I program less fuel at lower load changes and more at higher. Careful drivers can miss out on mileage as well by driving too slow (out of the engine's efficiency peak) or by not letting off the throttle quick enough to trigger decel enleanment. Pay attention on where your foot is. Only apply as much throttle as you need to maintain speed. There can be 'dead spots' in the powerband where added throttle really won't help accelerate the car, just burn more fuel.

 

Was I really that much of a granny driver? When I had the 2.8 mpfi I averaged 24~26 mpg in all city driving, and did even better on the highway... Heh then swapped to a hot rodded 350 and now get in the single digits more often than I should Oopsie

 

well the big throat is gone. the bottom latch thing was always open so it always let air in.. i tried to fix it.. no go. so i closed the bottom one with a screw driver and a hammer and put some j-b weld on the opening. so its completely sealed off.. how could i clean it? using solvents? or just some soap and a toothbrush? oh and where? the inside?? yeaa well i'm not a fast driver and i never want to get to the speed limit as soon as i let go of the break lol could i set my carb to let go of less gas? or that wouldnt deliver enough gas? hmm that question was confusing.. well how can i make a carb more efficient.. there ya go thanks again!

 

Get rid of it.

 

yeah, carb and efficient don't really go in the same sentence.

 

I used to get good mileage. 28-29 avg.

 

If he wants to do that I've got the top end of a 2.8 MPFI I wouldn't mind selling cheap, lol go go 3400 top end and 22.5 lb/hr injectors :P.

 

Well Jesus I get around 9mpg around town and maybe 14 on the highway. But that's cause my manifolds are cracked and my y-pipe is rusted out, sooo yeah my o2 sensor doesn't know what the hell is going on:/

 

Funny how people ask me why I bought a V6 Camaro rather then a V8 lol...

 

first tank with the car, 23 MPG

 

Wow know this is a dead thread but as for carbs/efficiency I get 23-25 around town and just had my first all highway run since I bought the car and got 31mpg, I was so surprised had to share this

 

im an 84 carbed 2.8 all stock... running 30mpg highway, probably 25ish city...

 

mileage, no idea, cars running to strange right now to get a good estimate on that, i'd say about 20-26 but idk, i'd love to get more once got 300 miles on half a tank doin about 48mph on the highway everybody else in the fast lane was pissed