25 mpg

[neanderpaul]

93 Auto. Was getting 33 in town, highway ac no ac. Took it on a road trip. Ran it hard. I.E. floored up mountains. Started getting 25 mpg. At that same time developed a slight miss - slight rough idle. No loss of power. New in the past 5000 miles: oil, oil filter, fuel filter, air filter, plugs, wires, dist. cap, rotor button.

So is this the O2 sensor? Maf? How do I test those things? Something else?

[92festie]

if its missing wouldnt that be a sign of bad plugs?? but i see you have recently changed them.....hhhmmm

[Team Lightning]

Still could be plugs that are bad. Also could be a plug wire has developed a break. Intermitten contact could cause a skip.

[TominMO]

Pull the disty cap, check for corrosion. Clean off if found.

[freshtiva]

if its missing wouldnt that be a sign of bad plugs?? but i see you have recently changed them.....hhhmmm

Ive had brand new plugs that were bad. Autos just dont do so well. May not be a problem at all. Ive had similar MPG in mine before. Depends on the factors. Id say hard mountain driving would do it.

[Festiva_Fred]

I bet I get 25ish sometimes.. during spirited driving on a hilly/curvy road..

[Pu241]

FWIW,I just finished towing another Festiva with an auto Festiva got 21 to 25 MPG between St Louis and Wheeling, WV.
Then drove it 400 miles from the east coast to Wheeling, WV and averaged 34 MPG.
When I drove 25horseplays favorite Festiva from St Louis to Wheeling I got 37 MPG.
All of this was at 55 to 60 MPH max.

[neanderpaul]

No it went from always getting 33 no matter the condition to always getting 25 no matter the conditions. I was 4000 miles in at 33. Now I'm 4 tanks in to getting 25.

I will check the plugs and dist cap even though they are new.

[neanderpaul]

Just saying it was a hard defined change. Now I'm back to same conditions that used to yield 33 and I'm still getting 25.

[resuwrecked]

It could be a bad coolant temp sensor, making it run richer. The 02 sensor wont have too much effect on fuel trim, but if shorted will ask for full rich, compounding the problem. You can try unplugging (or replace if you like) the 02 sensor for a tank and see what you get.
I have a wideband meter in my car and it actually runs richer all the time with it plugged in, (known good sensor). It does a very good job keeping afr's between 14.5 and 14.8 when cruising, idle, and light accel. With it unplugged I'm getting mid-high 15's and sometimes 16 cruising and 16 (as lean as meter will read) at idle, and as long as its not misfiring thats a good thing- saves fuel.

[TominMO]

I've heard that some places, like discount stores, might be getting spark plugs that are "seconds", not the best quality. So I always buy mine from a McParts store.

[JohnGunn]

If it's missing, BEFORE DOING ANYTHING ELSE, no matter when you last changed them, replace the plugs. Recommend NGK V-Power, but curious what brand you have been using. Bosch by any chance?

John Gunn
Coronado, CA

[neanderpaul]

Update. NGK is what I use. I pulled them they were all good. So plugs, wires, dist cap, rotor button, air filter, oil and filter, fuel filter all new and good. Today I'm borrowing a whole air box. I will run a tank out and check the mpg after that. I also may borrow an O2 sensor if that doesn't fix it. I still have an intermittent rough idle. I have all my power. No smoking.

[leapin]

Im working on the same thing right now. and seem to be at the same point.

[neanderpaul]

I couldn't get the air box today. I did get a bottle of fuel injector cleaner after my buddy Jack told me to today for the fourth time. Will report back.

Leapin, is yours an auto?