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Old 04-26-2018, 09:43 PM   #2 (permalink)
No idea what I'm doing
westb87's Avatar
Join Date: Apr 2018
Location: Huntsville, AL
Posts: 53

Sleek - '04 Honda Civic Coupe LX
90 day: 36.38 mpg (US)

Broomstick - '18 Volkswagen Atlas SE w/ Tech & 4Motion
90 day: 21.66 mpg (US)
Thanks: 15
Thanked 16 Times in 13 Posts
Originally Posted by Smithcraft View Post

I picked up a Civic EX automatic with ~190k miles, as something of an EmergencyINeedACarRightNow purchase.

I suspect it had been sitting for some time as it ran horribly rough, but it had had a new O2 sensor installed, just over a month or two prior.

When it was running horribly, it was getting around 32 MPG. Not too bad I thought.

Then I did a tune up with a new cap and rotor (both Standard Motors), new NGK V-Power plugs, and NGK plug wires. I also replaced the valve cover gasket. I figured with how much better it was running, the economy would have gone up.

Fuel economy took a dive down to ~28 MPG. I figured the ECU had to relearn timing and fuel metering.

A month or two ago, I posted about the undesirable fuel economy at Honda-Tech and it was suggested that I should inflate the tires to a higher pressure. I inflated them from ~30 PSI to ~35 PSI. The economy went up to ~28.5 MPG.

It was still running rough, so I adjusted the timing and got it fairly close. Economy dived down to an average of ~25 MPG for that week. Granted there was a lot of idling when I adjusted the timing. With a coworkers help, and his really fancy timing light, we were able to get the engine timing to be spot on, and it runs very smooth. It's almost nice to drive around town, but still rough on the highways (the tires are terrible Les Schwab tires). The economy on that tank was down around ~24 MPG. When I fuel up tomorrow I'll have a complete week on the current timing. And that average was 25.7 MPG

So, I'm not looking to hypermile, but I'd like to get decent economy out of this car! At ~24 MPG, I might as well be driving a a turbo Subaru!

Hopefully I can get some suggestions to get this car running better!

If it helps, my 04 Civic isn't getting the mileage (while hypermiling no less!) that many others are able to get while driving like they are at the races. I'm getting an average read of 30-31 mpg. I'm not sure what my issue is either. I've got the engine and transmission running much better than when I bought the car. I'm not going to get wrapped around the axle about it, but it IS annoying. Best of luck my man.
Sleek (2004 Honda Civic LX Coupe, Auto). The Commuter

Broomstick (2018 Volkswagen Atlas SE w/ Technology & 4Motion All-Wheel Drive), Auto 8-speed with "Tip-tronic". The Family 'Wagen...also the weapon of choice of the "Wicked Witch of the Wests" a.k.a The Wife.

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