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Old 03-29-2018, 10:43 AM   #1 (permalink)
EcoModding Lurker
Join Date: Mar 2018
Location: North Covington, WA
Posts: 8

98 Civic EX - '98 Honda Civic EX
90 day: 27.12 mpg (US)

08 Legacy SpecB - '08 Legacy GT SpecB
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Hello from the PNW with a 98 Civic EX


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!


Last edited by Smithcraft; 03-30-2018 at 01:20 PM.. Reason: Add the most recent MPG average.
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