Lost 6mpg

[Evil D]

Well i did find a vacuum leak today...but it couldn't have been disconnected very long. It's the line that operates the trap door valve in the breather housing for the heater hose...go figure, the damn thing actually works. So now i have that line plugged, because even after warming the car up, the valve stays shut trying to pull air out of the tiny little preheater hose on the bottom of the snorkel. I'm pretty positive there's no vacuum leak now, and i can't find any hint of a gas leak...no smell, no dripping on any lines i can see. The vacuum leak could be part of why my last tank of gas sucked so bad..we'll see.

[Safety Guy]

Yes, I'm pretty sure the stock Aisen carbs are part of a feedback loop system.

The reason I'm so sure (without going to get my '89 manual) is that, fed up with the bureaucracy at work several years back, I marveled that the difference between a bunch of incompetent administrators and a Festiva carb is that our carbs at least give feedback!

I consider our carbs to be smarter than the Pathological Administrative Subculture.

Yep.

Karl

[Pu241]

Carbie, should have known wasn't EFI as you mentioned shifting earlier.

Don't know if theses are feed back carbs or not someone else will need to chim in on this!

[Evil D]

It's a carbie....is there even such a thing as open/closed loop on them? I haven't smelled gas anywhere but i'll check the fuel lines for signs of leaks. I have replaced the fuel filter though (which was pretty clean to begin with). It doesn't smell rich or anything either.

[Pu241]

Ah, another clue.
My engine doesn't even get up to temp, at highway speeds, till I've gone 5-7 miles.
My guess is your engine doesn't get into closed loop mode before your at your destination and shut down.
Then do it all over again when you go home.
That still doesn't explain the drop from your July average, of course your fuelly data only goes back to August 2nd.
But, that shows 3 tanks averaging about 32 MPG then a drop in the next two tanks, then back to 32+ MPG. So what happen with those two tanks, because as late as Oct 11th the car still was capable of 32+ MPG on your daily commute?
I do agree the temp plays a roll.
I wonder now that the temp are much lower, probably what 40 degrees, from say even Oct, that as I mentioned your car never heats up enough to get into closed loop mode and it higher combustion efficiency.

[GenevaDirt]

maybe fuel return line is plugged up....fuel leak somewhere?

[Evil D]

It's a stick. Look at how it's dropping off on my Fuelie graph...it's so sad

There isn't any noticeable loss in driving or performance. It fires right up and drives like it always did.

[GenevaDirt]

wow.....that mileage is WAY low....
do have an auto or stick? My auto get about 35mpg in the winter...a little higher in the summer even running my air. You numbers are telling me something else is wrong.

[Evil D]

Well, i did a full tune up when i first got it but i haven't pulled them to see if they're fouled out. The most driving i do is to and from work, which is about 7 miles one way and has a fair amount of stop lights and stop signs, and only two stretches of non stop driving which are maybe 2 miles each and both are 45mph.

[Pu241]

it always seems to me that whether i run my car hard or not it gets about the same mpg

Do you actually keep a log and calculate MPG or is this, as most people do, seat of the pants cyphering?

Yes; I noticed about a 6 to 8 MPG drop in my 88L (carb) since the temp has dropped here in central PA. Going to be “custom” fitting a nice piece of card board over the rad. here soon.

The "custom cardboard" option will help and make your heater run a little warmer, but I've done a full grill block and that should also keep the cold air from cooling the engine directly. Was even thinking of blocking the lower bummer opening to minimize air flow into the engine compartment. At these temps the fan isn't likely to come on, and if it did there is enough room between the grill block and the radiator for the fan to move air through it and extract heat.

Well 6mpg would be a welcome loss now...i've gone from a 30-32 average to 23-25. The car is running as good as it ever has, so i'm blaming the weather and crossing my fingers that that's all it is.

I still think that MPG is low.
Even given the weather (note it was low in July too) and your nearly 100% city driving.
I think something else is wrong somewhere.
Have you checked the spark plugs for fouling and/or other combustion related clues.
Anyone else have MPG data for 100% city driving?
Mine won't be of much help as mine is nearly 100 Highway.

[Evil D]

Well 6mpg would be a welcome loss now...i've gone from a 30-32 average to 23-25. The car is running as good as it ever has, so i'm blaming the weather and crossing my fingers that that's all it is.

[Kbrier]

Yes; I noticed about a 6 to 8 MPG drop in my 88L (carb) since the temp has dropped here in central PA. Going to be “custom” fitting a nice piece of card board over the rad. here soon.

[Evil D]

it always seems to me that whether i run my car hard or not it gets about the same mpg

That's what a lot of people have been telling me...i just figured i'd give this a shot and see. I'm not concerned enough with it to drive 50 on the local interstates...that's suicide around here.

[LoneManWolf]

it always seems to me that whether i run my car hard or not it gets about the same mpg

[ejp2fast]

my 2 cents is that the festiva gets the best mileage non-stop driving at 50-55 mph...
don't know if thats "highway" or not, but thats been my experience...