97 DX Startup Idle and Low MPG?
#1
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97 DX Startup Idle and Low MPG?
Hey everybody,
I have a 1997 Civic DX Hatchback 130,7XX, and I was throwing a CEL P0421 or P0420 code back in July. I checked the exhaust manifold and it was cracked in the center, so I had that replaced along with the catalytic converter. I also replaced the oxygen sensor on the manifold because the light came back on. I also changed a valve near the air box which I heard can throw codes like that. I had been getting about 35-40MPG before the issue. While I had the CEL on, I would get about 22, and now I get about 30 driving either highway or city with no CEL.
I'm wondering what the issue could be that I don't get the mileage I used to (35-40). I don't have anything heavy in the car. I replaced the tires about 2K miles ago, but that shouldn't cause that much of a difference in MPG. Could it be the lower oxygen sensor? I also notice at startup that the car idles high but then lowers to the normal level after about a minute. I work at AutoZone so I could get discounted parts. I'm thinking it could be dirty injectors, the fuel filter, or that other oxygen sensor. Any suggestions? All help is appreciated.
I have a 1997 Civic DX Hatchback 130,7XX, and I was throwing a CEL P0421 or P0420 code back in July. I checked the exhaust manifold and it was cracked in the center, so I had that replaced along with the catalytic converter. I also replaced the oxygen sensor on the manifold because the light came back on. I also changed a valve near the air box which I heard can throw codes like that. I had been getting about 35-40MPG before the issue. While I had the CEL on, I would get about 22, and now I get about 30 driving either highway or city with no CEL.
I'm wondering what the issue could be that I don't get the mileage I used to (35-40). I don't have anything heavy in the car. I replaced the tires about 2K miles ago, but that shouldn't cause that much of a difference in MPG. Could it be the lower oxygen sensor? I also notice at startup that the car idles high but then lowers to the normal level after about a minute. I work at AutoZone so I could get discounted parts. I'm thinking it could be dirty injectors, the fuel filter, or that other oxygen sensor. Any suggestions? All help is appreciated.
#2
If you think a good mechanic is expensive, try hiring a bad one
Re: 97 DX Startup Idle and Low MPG?
I work at AutoZone so I could get discounted parts.
What brand was the O2 sensor you installed?
I also replaced the oxygen sensor on the manifold because the light came back on.
I also changed a valve near the air box
which I heard can throw codes like that.
I don't get the mileage I used to (35-40).
get about 22, and now I get about 30 driving
get about 22, and now I get about 30 driving
Check cam timing first.
If that's ok, then unplug the first O2 sensor and drive it a few days, see if there is any improvement.
#3
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Thread Starter
Re: 97 DX Startup Idle and Low MPG?
I don't know much about Honda engines as this is my first civic and I've had it for less than a year. I replaced it with a Bosch sensor.
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