Engine running rich, poor MPG.
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Engine running rich, poor MPG.
Sorry for posting this in the 7th gen forum but it gets more view/replies. There should just be one mechanical problem forum imo.
97 civic dx:
I'm not throwing any codes, but the engine seems to have too much power. I barely have to touch the pedal and I'm flying around everywhere. I used to get 34-38 mpg consistently, but now I cannot get past 33 and recently I got 31 mpg. The engine holds a steady 670rpm and the timing is correct.
Everything here is in good shape:
Ignition timing
The throttle cable is in spec.
Fuel filter, air filter
Plugs, wires, rotor, distributor cap
Ignition coil, MAP, air sensor, 02 sensors
Fuel pressure regulator
Any ideas of what it could be?
97 civic dx:
I'm not throwing any codes, but the engine seems to have too much power. I barely have to touch the pedal and I'm flying around everywhere. I used to get 34-38 mpg consistently, but now I cannot get past 33 and recently I got 31 mpg. The engine holds a steady 670rpm and the timing is correct.
Everything here is in good shape:
Ignition timing
The throttle cable is in spec.
Fuel filter, air filter
Plugs, wires, rotor, distributor cap
Ignition coil, MAP, air sensor, 02 sensors
Fuel pressure regulator
Any ideas of what it could be?
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
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From: Midwest. Aiming about mid-chest
Rep Power: 517 Re: Engine running rich, poor MPG.
the engine seems to have too much power. I barely have to touch the pedal and I'm flying around everywhere.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517 Re: Engine running rich, poor MPG.
Winter fuel/oxygenated fuel kills gas mileage. Period. (I see where you are, you still get it every year.)
My car dropped almost 6 mpg (city) as soon as i got the first tank this season. Part of it has to do with the cold weather too, but WOW.
I can't tell if highway mileage dropped solely because of the fuel, because I stuck on 18" rims and 225 tires on it earlier this month. But highway mileage was effin miserable on my 300 mile jaunt at Xmas.
My car dropped almost 6 mpg (city) as soon as i got the first tank this season. Part of it has to do with the cold weather too, but WOW.
I can't tell if highway mileage dropped solely because of the fuel, because I stuck on 18" rims and 225 tires on it earlier this month. But highway mileage was effin miserable on my 300 mile jaunt at Xmas.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517 Re: Engine running rich, poor MPG.
What's the operating temp?
A thermostat that is even slightly flaky can drop your gas mileage quite a bit.
A thermostat that is even slightly flaky can drop your gas mileage quite a bit.
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From: Reno, NV
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Operating temp? You mean on my dash or where I drive? It's been snowing here; cold and humid weather. I have been pushing my car harder than usual too, so maybe that's also a factor, but I do wonder about that thermostat. Don't they throw a code if they go bad? How long do they typically last?
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517 Re: Engine running rich, poor MPG.
Operating temp? You mean on my dash or where I drive? It's been snowing here; cold and humid weather. I have been pushing my car harder than usual too, so maybe that's also a factor, but I do wonder about that thermostat. Don't they throw a code if they go bad? How long do they typically last?
Operating temperature of the engine after warmup.....
What the thermostat regulates the temperature at while driving.
Once the engine is warmed up, the temp should never drop below the thermostat rating.
If you have a stat rated at 180*F, the coolant temp should not be 170 when driving down the road (after warmup).
Temperature as seen on a scantool datalist, reading the ECT sensor.
Gauge on the dash is not accurate enough for this.
(Also consider the possibility of an inaccurate temp sensor for the PCM.)
No, it does not have to "throw a code" (depends on the criteria programmed if the PCM and regulations of the model year in question).
A thermostat is "good" until it is "bad".
Please use a factory stat if you decide to change it. Aftermarkets are a crapshoot.
Thread Starter
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From: Reno, NV
Rep Power: 266 Re: Engine running rich, poor MPG.
I almost always go oem but the thermo is aftermarket in mine. I think I replaced it at 100k, and I've got 156k now.
I will check the temp with a scan tool when I get a chance, thanks.
I will check the temp with a scan tool when I get a chance, thanks.
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