WKD DRGN

I am still having very poor gas mileage and am trying to figure out what the graphs mean as to what the problem might be with my car.

I have been watching videos to learn about STFT and LTFT but am confused with the mapping of the graphs.

My car was getting 28-30 mpg but now is getting 23 mpg or less.

Can someone explain these graphs to me?

Poopies

iTrader: (4)

How are you calculating your mpg?

ezone

STFT .78? I can't tell how much of the time it's in that range, it looks like it nears 0 part of the time. Describe more?


LTFT looks in a normal range, less than 10% is good.

What front O2 sensor is? Original? Replacement? OEM?

WKD DRGN

My dad inputs my mileage after each full tank fill up into some program and it averages it out and such. He always keeps track of my mpg.

Both oxygen Sensors are replaced with NTK. Was thinking about putting the oem ones back on if I still have them.

If I put the engine in park and idle it and then Rev and hold the rpms around 1500 - 2000 the STFT goes up but spikes like you see in the graphs. Up and down and up and down. If I drive it, the STFT fuel curve goes up with engine speed but still spiking to some degree. It's not a smooth curve. I was thinking that it might be a fuel delivery problem from the videos I've been watching but the spikes are throwing me off. Wondering if it might be a vacuum leak? There is no CEL. I have no idea. And am kind of scared of doing the whole spray stuff around the engine bay to see if there is a leak.

ezone

STFT should change rapidly and often, technically it is changing with every transition of the front O2 sensor.

If you graph the front O2 sensor along with the STFT you may see more of this.

Hot engine:
What is STFT -- idling in neutral? (rough average number)
What is STFT -- idling in drive?
What is STFT -- at 2000 RPM in neutral?

What is the LTFT range under all these conditions?




With fuel trims, base calculation without correction is 0 (%). This is calculated from temperatures, load (MAP in this case), and RPM inputs.

Corrections to fuel trims come in when O2 sensors are read and used for additional calculation. The sensors are the "feedback" the computer is looking at to measure the oxygen content in the exhaust.

(Your .78 number is the equivalent of -22% STFT, which would be removing fuel from the base calculation. Computer thinks system is too rich and is removing fuel.)

WKD DRGN

Okay got some more graphs/readings from under the conditions you asked about.

STFT
Idle in Park is reading in range of
-1.49%
-0.69%
-2.29%

STFT
Idle in Drive
-0.77%
-1.55%
-0.78%

STFT
Neutral @ 2000 RPMs
-3.11%
-4.67%
2.34%
-2.33%
-7.02%
3.9%

LTFT
Park
Neutral
Drive
All average out at -0.78% to -0.77%

Graphs to follow (graphs are showing correlation between stft and bank 1 sensor 1 %)

ezone

I think I may be confused as to how your app works.
I may have interpreted your .78 as lambda instead of %, or based the starting point as 1.00 instead of zero.
There are several different ways of reading trim values.

Anything within 10% fuel trim correction is usually OK.
Codes don't start happening until you hit the 20% correction range.

WKD DRGN

Took it to the dealership they didn't want to bother with it. Took it to meineke they said there's no exhaust leaks at least. That's about all they could do. Took it to a mom & pop shop I know through our work. And asked if they could check for vacuum leaks. He didn't think it was a vacuum leak but found my distributor was off alignment from the line. I *think*he rotated it back towards the firewall. And the engine sound changed. The car has been running sluggish the last couple of days. And shifting bad again. The mechanic doing this made the pep come back and the shifting smooth out. Idk know what or if it will improve my poor mpg. Got a full tank to day so will know in a week. Thing is I don't know how the distributor was moved from its spot unless it's been moved since June when they put the transmission back in? Idk. Will keep you updated.

ezone

Well that would explain it, but how in the hell did it get moved? Did someone pull the trans out the top????



Paraphrased from a tech class: "Once distributor timing has been set, it should never ever need to be moved for the rest of its natural life.

If anyone thinks it needs to be moved, there are 3 hold down bolts so one would need to make at least 3 mistakes before they can move it."

(Some distributors use 2 bolts, but you get the idea.)

I rarely think of ignition timing mainly because it should never need to be touched. Sometimes there is telltale evidence like witness marks where the bolts were if someone moved it recently. Along with a lack of power and slowed response on snap throttle.

Didn't jump the timing belt, did it?

WKD DRGN

I have no idea how it was moved or why. There was a white line drawn on top to line it up. Anyway it worked cause my car is shifting perfectly, is full of pep and is back to its normal gas mileage. It's sad I spent all that money on tune up and other parts when I should have taken it to this shop first. But I never know which shop is gonna find the problem. Either way I'm estatic to have my good gas mileage back. Thanks for all the input.

-Kristy

ezone

Maybe a previous shop? Was there a shop visit shortly before you noticed the problem?

Someone unscrupulous trying to generate more revenue?


If this wasn't the shop that broke the car (see comment above), I think this one should go on your speed dial.

Figure out who the tech was that found the problem and request him whenever you go.

WKD DRGN

I don't think it was at a shop when the problem started. The only thing I can think of is maybe like long ago when I changed out the distributor cap and rotor maybe I mistook the distributor bolts as the ones that held the cap on and accidently adjusted it. Or maybe my dad adjusted it at some point trying to fix something. Advice noted about leaving it alone though.

The shop I took it to is a local shop ran by a wife and husband and the husbands' dad. We're pretty close professionally wise. They came to my small wedding. Lol. I usually don't always take it there cause the husband likes to say just turn up the radio if I hear weird sounds. I'd rather him find the issue but I think he says that when he thinks it's insignificant. I still like going to them though. They're honest and very reasonable. Too bad they don't do alignments.

ezone

I suggest the radio fix as humor once in a while. Usually for noise complaints that aren't serious.
I don't normally joke about stuff that would be dangerous like suspension problems.

We all have strengths and weaknesses.
I hate trying to find random faint squeaks and rattles in the interior, but I love the driveability and electrical problems that nobody else can figure out.

Darn tough to do that over the internet though.

WKD DRGN

I went back to Honda just to let them know I had the problem fixed and what the solution was. They asked if the distributor o ring had ever been changed and at first I said no but then remembered I had another shop do that within the last 2 years cause they said it was what was causing a leak. So that must have been it to why it was out of range. Thanks again.