25 mpg

[leapin]

Nope, 5 speed. Im curious to know how the cleaner works for you.

[mr2gq]

could be a vac leak causeing missfire. Also a bad fuel pump will too. They got a tool at the part store you can check while hte car is running to see if a sparkj plug wire is getting spark. Maybe could be a wire even though is new. Thats happend to me before

[neanderpaul]

But I have full power.

[eurotiva]

Paul just let me put a turbo on it and you'll never notice any power issues.

[neanderpaul]

The B6t is going in it this spring!

[mr2gq]

just cause you have full power doesnt mean it couldnt be one of those. It could also be a injector o ring or a "sticky" injector. It could be a number of things causing a slight miss fire with bad mileage. Just have to trouble shoot

[neanderpaul]

Ok that's why I posted here. To find out how to trouble shoot.

[JohnGunn]

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.

I think you are misinformed if you think you can always spot a bad plug by looking at it. When my Bosh plugs failed after less than 5,000 miles they looked perfect. I would still say replace the plugs no matter when replaced or how good you think they look. Nothing lost, but face, at this point.

Ok that's why I posted here. To find out how to trouble shoot.

On trouble shooting: Never be as sure as you appear to be, that anything is "new and good." If you are wrong about any of the items on your long list of "new and good" items above, you will be doomed to continue replacing parts until all parts are "new and good" and have before you a "new and good" Festiva that has the same problem. I stress this because I was well along that path myself.

Another good idea would be to focus on one problem at a time. For example, here, you are concerned about your mileage and mention you have a rough idle. Now, I think those two problems are probably related, so forget about anything else and address the problem that is easier to observe, where you can make a change and immediately know whether it had an effect, in this case the rough idle. Applied to the problem at hand, I might want to replace the plugs one at a time checking the effect on the idle after each new plug was installed. In addition, if you grounded the terminal used in setting the timing, you could eliminate any interference from the computer as it works to maintain idle speed. Then you might be able to judge the effect of each new plug in terms of how it affected the true speed of the idle, rather than idle speed as corrected by the computer.

If you did that and could say the new plugs made no difference, I would say you could label the plugs that you just replaced as "new and good" and move on to the next most likely suspect.

A rough idle that is consistent is most likely an ignition problem, much less likely to be caused by poor fuel delivery, mostly because all the things that might affect fuel delivery do not act as immediately as an ignition failure. Of course, it is possible, if you are clever enough and determined to prove something, to justify replacing just about anything no matter how unlikely. That is not advised. Much better to thoroughly test and eliminate the most likely causes before allowing your imagination free range to invent theoretical connections to unlikely suspects. In your case I could imagine a rough idle to be caused by "clogged" injectors, whatever that means, and could quickly convince myself that if the injectors are all providing different amounts of fuel the idle will be rough, or at least uneven. But when I have had a rough idle in the past, that was never the problem.

I can see how a bad oxygen sensor would cause poor mileage, in fact that might be high on my list of suspected parts, but if it is bad enough to drop your mileage by 15 MPG you should have some indication of the engine running rich, soot on the spark plugs and at tail pipe. The oxygen sensor is another part associated with fuel delivery that acts slowly. Still it would be easy enough to ground the set timing terminal and unplug the oxygen sensor to see if it had any effect on your idle problem.

John Gunn
Coronado, CA

[FB71]

Paul, not thinking too clear at the moment, I'll get with you tomorrow (monday 4/19), but Gunn is on the right track. Unplug the O2 sensor for a few days, see if that makes a significant difference in mileage.

[neanderpaul]

Dig it. Will do. thanks!

[Britstiva]

Wow, I'm curious to see if this fixes the problem. Bristiva is a 4spd/carb'd and the mileage is terrible for a Festiva. I've never calculated it, but definitely know it's not getting the gas mileage it should be.I

So it may be having the same problem!

[neanderpaul]

You know Jerm, I have had a couple of carbys with 4 speeds that got around 30 in town running hard delivering food. But they were FAST for real. It was tolerable because it was a trade off. But my auto is still a dog from 0-25.

[Pu241]

Wow, I'm curious to see if this fixes the problem. Bristiva is a 4spd/carb'd and the mileage is terrible for a Festiva. I've never calculated it, but definitely know it's not getting the gas mileage it should be.I

So it may be having the same problem!

You know hard numbers help considerably with diagnoses.
Calculation of MPG is not quantum mechanics and could provide useful data!

[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.

I'm just the guy that knows how to spraypaint...

[neanderpaul]

I'm just the guy that knows how to spraypaint...

I'm trying one thing at a time. The only thing I've tried so far for one tank was the fuel injector cleaner.