Lost MPG after Tune Up on Honda VX - Fuelly Forums

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Old 08-22-2008, 08:46 AM   #1
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Lost MPG after Tune Up on Honda VX

Hi Everybody,

Got a odd ocurrence with my VX. After a tune up of
  • Mobil One 5w-30 oil change
  • Fuel filter
  • Cap and rotor
  • Spark plugs (NGK ZFR4F-11)

My MPG DROPPED 7 Miles per gallon or about 15%
(From Nearly 50mpg to 43mpg)

What on earth has happened? I thought I'd see a little increase not a large decrease.

Please offer some insight if you can

Thanks
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Old 08-22-2008, 10:15 AM   #2
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Originally Posted by SuperVX View Post
Hi Everybody,

Got a odd ocurrence with my VX. After a tune up of
  • Mobil One 5w-30 oil change
  • Fuel filter
  • Cap and rotor
  • Spark plugs (NGK ZFR4F-11)

My MPG DROPPED 7 Miles per gallon or about 15%
(From Nearly 50mpg to 43mpg)

What on earth has happened? I thought I'd see a little increase not a large decrease.

Please offer some insight if you can

Thanks
It is running "right" (besides fuel consumption)?
Did you do the work?
Was the timing checked?
Are all the vacuum lines re attached?

I very often overlook something or do something wrong when I work on my car and usually need to go back double check everything to dial it in.
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Old 08-22-2008, 03:44 PM   #3
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I'm assuming you did the work. Did you gap the plugs? Like mini-e said, check for loose connections, wires, hoses. If you have the old cap and rotor, you can try putting them back on and see if you get a difference. You lost a little fuel replacing the filter (admittedly, not much). Lastly, your new mpg number is only based on 8.5 gallons, so you may get a rebound with your next fill up.

Bill
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Old 08-22-2008, 07:57 PM   #4
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Originally Posted by Nrggeek View Post
I'm assuming you did the work. Did you gap the plugs? Like mini-e said, check for loose connections, wires, hoses. If you have the old cap and rotor, you can try putting them back on and see if you get a difference. You lost a little fuel replacing the filter (admittedly, not much). Lastly, your new mpg number is only based on 8.5 gallons, so you may get a rebound with your next fill up.

Bill
I would not base any mileage change on one tank. The gas pumps can click off at different levels. If you check my gas log on July 10 I miraculously have a 50mpg tank when I used a different pump at the same station. Next tank I rebounded the wrong way at 35mpg.

If your next tank is low then maybe you have something to look into.
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Old 08-22-2008, 09:24 PM   #5
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Mini-e
Thank you for your response
Is running the same
I did the work
Timing was not check (not sure why it would need to be)
Didn’t touch any vacuum lines
I will double check my work, I to make mistakes…

Nrggeek
Thank you for your response
I gapped the plugs (.043) and used the factory plug. This is the place I’d look into first. Recheck the gap. Buy the same plugs that I pulled out and last there are fancy new plugs that don’t need gapping. I’ll play with this one. I’m not sure how a new cap and rotor can cause a problem? The first sign of troubles was the gas gage being in the wrong place for the miles traveled. I filled the tank. Divided the miles traveled by the fuel just put in the tank to come up with my mileage. The fact that the tank was about 1/3 empty before the tune up tells me that the MPG will be even worse at next fill up.

Rex-O-Saurus
Thank you for your response
I realize that pumps stop at different points. But 15% decrease in MPG?
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Old 08-22-2008, 10:37 PM   #6
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[QUOTE=SuperVX;116036]Mini-e
Thank you for your response
Is running the same
I did the work
Timing was not check (not sure why it would need to be)
Didn?t touch any vacuum lines
I will double check my work, I to make mistakes?



i like to check timing if i open up the distributor and change the cap just in case it clocks a bit different or there is a difference in parts. i have a volvo 850 that i changed the cap/rotor on and i did not seat it properly- the car ran so- so for a year untill i re visited the work i thought i had done right and caught it.

checking timing is a basic given to eliminate if something is off.

since that car is running well i too would run through another tank and check the millage and see what number you get before taking things apart. it could be a few things- wires not pushed on the plug(s) quite all the way, rotor not seated properly- old wire(s) gave up when you yank them off the plugs- good luck! (nice car...)
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Old 08-23-2008, 12:35 PM   #7
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Quote:
Originally Posted by SuperVX View Post
Mini-e
Thank you for your response
Is running the same
I did the work
Timing was not check (not sure why it would need to be)
Didn?t touch any vacuum lines
I will double check my work, I to make mistakes?

Nrggeek
Thank you for your response
I gapped the plugs (.043) and used the factory plug. This is the place I?d look into first. Recheck the gap. Buy the same plugs that I pulled out and last there are fancy new plugs that don?t need gapping. I?ll play with this one. I?m not sure how a new cap and rotor can cause a problem? The first sign of troubles was the gas gage being in the wrong place for the miles traveled. I filled the tank. Divided the miles traveled by the fuel just put in the tank to come up with my mileage. The fact that the tank was about 1/3 empty before the tune up tells me that the MPG will be even worse at next fill up.

Rex-O-Saurus
Thank you for your response
I realize that pumps stop at different points. But 15% decrease in MPG?
Don't know about the gas pumps in Tenn, but in CA we have the pumps that scavenge the fumes out of the tank, some are more sensitive then others. I stop filling at the 1st click and I've definetly seen different pumps click off at different levels. The only way I am consistent is when I use the same pump to fill my car. When that isn't possible, I usually have a higher or lower mpg tank followed by the next one that counters it. Your 15% drop is about 0.8 gallons.
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Old 08-24-2008, 08:48 AM   #8
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I'm new here, been 'lurking' for awhile. Hope I can learn/help.
I work with fractional distillation(cryogenic) and deal with flows,temps,pressures, and fine analysis to PPB.
I also am a lifelong gearhead from b/stratton to aa/funnycars, taken my Ranger from 19 to 28mpg, my sons CRX to 50+ a few times. We get into it.

Great input here, here's a few other possibilities;

You need to know the quality of the fuel. 'E' fuels can and do vary greatly. I find 3-15% 'E' in 'E10' to be normal!!??!! They also can have up to 8% water in 'E' by law(10oz/gal). It is not economical/possible to make 100% pure 'E'.

Pump Calibration can vary. Your state will have a spec as to +/- allowance.
They should be caled annually, and have a tag on the pump. The ONLY way to know is to check it yourself. Pumps are just machines, as good as their P/M program.

Station pumps are not temp/pressure compensated. Time of day/weather has a small impact here.

Each one of these alone shouldn't be a BIG factor. However, if the planets are all in alignment-----?????? +/- 10% is very possible.

1000-1500mi is my point of pain with +/-. The higher mpg you get the more impact there is.

Good Luck, this crap happens to me tooooo often with 4 cars to track.
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Old 08-24-2008, 05:48 PM   #9
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I've personally had significant differences on one tank compared to another on my VX.

I wouldn't worry about a single tank, look at averages.
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Old 08-25-2008, 08:31 PM   #10
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Thanks Danronian,

I might just be freaking out over nothing. The gas gage seems to have slowed down (to normal?) I'll post the mpg after this tank.

Sweet paint job on your VX.

Thank again everybody for your time and input
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