Auto festiva is getting 25 mpg :(

[mraz]

So my 1990 festiva is a auto 3 speed and i drive it fairly hard but 25 mpg seems very low.. 3 of my buddys driving equally hard with there 5 speeds with fuel economy ranging from 37-44.

My engine is stock efi with 78783 miles the resignator and muffler have been removed and replaced with 1.75" exhaust following stock location, it has 8mm wires and plat/plugs, fuel filter is new, and air filter is new. Is my cat/conv maybe clogged? also im thinking about pulling a cone filter on and removing the noise reducer for mpg gains.. im up for ideas ha 25mpg makes the festy not even worth driving

[Slyder]

hmm. well, i dont know much about this but what about your O2 sensor. i do believe that can significantly reduce fuel economy if not working properly. are you running on all cylinders? i would check plugs, wires, etc. or possible your timing is way out. thats all that comes to mind for me. hope this helps.

[TominMO]

25 MPG for an auto might not be that low if you drive it hard, esp. in the city with fast starts off the line. 37-44 is pretty normal for a 5-speed.

The cat should be fine with the mileage you have. Try switching to NGK BPR6ES-11 plugs; this motor may not like the platinums, but other members here will possibly know more about this. Air filter changes (other than a clean filter) won't help mileage. Make sure your tires are aired up to at least 30 PSI. Make sure your e-brake isn't dragging too.

The right foot is by far the main determinant for gas mileage. Try driving it conservatively for a 1/2 tank or so and notice the change. Shut off the motor if a stoplight has just turned red on you and you know it's a long light. Also, if you're checking mileage, make sure you fill up the tank the same way both times, preferably at the same pump, and rock the car a little to "burp" the gas tank.

[FestYboy]

no platinums for the B series engines! they don't like them at all.

[eurotiva]

^^X2

[mraz]

no plats huh that might do it ill go get some plugs... i run 50psi in my tires not to worried about them wearing out 10 bucks a piece from the junk yard with rims so i have a few sets..

is there anyway to trick my little b3 into running lean?

my other thought is play with the amont of fluid in my tranny... i know too much kills power and mps.. so maybe less= good ? just a thought

[i218127]

Get the tranny serviced (Complete drain and refill). "Sea Foam" for transmissions may also help. I had my sister do it (she has a Stratus with 75 thousand miles) and it worked wonders for both mileage AND performance. Automatics are not indestructible, and are a critical link to the ECU. They BOTH must work correctly. 5 speeds are mechanically linked. The ECU doesn't care what the manual is doing. It only deals with the results of a manuals actions.
A suggestion.

"Drive On...ARMY"

[FestYboy]

the autos aren't linked in any way to the ECU, it's a mechanical auto. ant don't mess with the fliud levels, too much will just expand and push out the vent tube, too little will butn up the clutch packs and ruin the trans. just run fresh fluid at the propper level and monitor the o2 sensor (reply with results).

[i218127]

I only give advise. I'm told, the more advise you get the more choices you have. Not sure if NOT servicing the tranny is good advise. Even if there was a technical error in linking the transmission to the ECU, following normal service intervals can't be all wrong. Fifty thousand (50K) seems average for most cars. Seventy eight thousand (78K) may be a little long. I suspect SOMETHING will improve when the fluid is changed.


"Drive On...ARMY"

[FestYboy]

i agree completely

[freshtiva]

Auto festivas never were good on gas. They are too low geared.

[mechanicaldj]

33mpg combined is what i had on my 1991 auto(bone stock)

loose the platinums and try some NGK V-powers instead
and check the distributor secondary circuit contacts for corrosion

[TominMO]

And take about 10% off that window sticker's 31/33 mileage rating, as the method they used to come up with those numbers wasn't very precise.

[Schildir]

And take about 10% off that window sticker's 31/33 mileage rating, as the method they used to come up with those numbers wasn't very precise.

I have an '89 auto, and I beat both those numbers without really trying hard to drive economically. Just wanted to mention that, even if I am an exception to the rule.

[TominMO]

I have an '89 auto, and I beat both those numbers without really trying hard to drive economically. Just wanted to mention that, even if I am an exception to the rule.

Yeah, it's certainly possible. In my '90 5-speed, I have gotten 50.5 MPG in city driving by using hypermiling techniques; and 58.5 MPG at a steady 55 MPH.