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Leaky Valve Cover Gasket = Bad Gas Mileage?
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Tikiman
New User
Dec 20, 2013, 8:04 AM
Post #1 of 6
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Leaky Valve Cover Gasket = Bad Gas Mileage?
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2006 Honda Civic LX
160,000
Our car used to get around 370 miles for a tank of gas. Suddenly we can barely make it to 300. I know the gas blend changes in winter, but it has never made such a drastically noticeable difference.
We brought the car to the mechanic who could find nothing terribly wrong... WE changed the spark plugs, and had a fuel induction/body throttle service which didn't make any difference to the bad mileage.
We also brought it back to the Honda dealership who recommended a few things, but nothing made a difference.
However, one of the things they recommended which we haven't done yet, is a leaky valve cover gasket. Could that be the cause of my problem? Could it be causing a lack of pressure in the engine? MY mechanic didn't catch mention it, only the dealer... But since I came in complaining of poor mileage, I would think they would have suggested that if they thought it was the cause, but maybe they just didn't put it together?
I know I should probably have it done anyway but if this poor mileage continues I may not want to put any more money into the car and just get a new one.
Thanks for your help..
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 20, 2013, 8:18 AM
Post #2 of 6
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Re: Leaky Valve Cover Gasket = Bad Gas Mileage?
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No, a leaky valve cover with not effect fuel mileage unless it gets so bad that it submerges the spark plug in oil and then there would be an obvious misfire that no one has mentioned so I doubt it.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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GC
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Dec 20, 2013, 8:20 AM
Post #3 of 6
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Re: Leaky Valve Cover Gasket = Bad Gas Mileage?
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Im assuming cel is not on, since not mentioned. Are you warming the car up in the morning, leaving it idle? How cold is it there? Weve had an uncommonly cold start to winter here, and everyones fuel economy has gone south. Idling the car to warm it up and clear ice, cold air temps, winter blend or some water contamination in fuel - all contribute.
edit: Are you getting good heat inside the vehicle? Does it warm up in the same amount of time as before? What does temp gauge say? Would think that a thermostat or temp sensor would have been caught at this point...
____________________________________________________
Willing to help, willing to learn... Rob
(This post was edited by goiserclause on Dec 20, 2013, 8:39 AM)
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nickwarner
Veteran
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Dec 20, 2013, 8:21 AM
Post #4 of 6
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Re: Leaky Valve Cover Gasket = Bad Gas Mileage?
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You changed the spark plugs, but did you change the coil boots? Was there oil around them when you did the plugs or where they dry?
The valve cover gasket has nothing to do with any pressure. It simply keeps the oil from leaking out of the top of the engine. But in a DOHC motor, the spark plugs are way down in the middle and there are round seals as part of the gasket kit in the valve cover to keep the oil from leaking into the spark plug tubes. If oil is in there, some of the energy from the coil will short to ground instead of going through the spark plug. You get a weak spark which will give you poor mileage. It will also deteriorate the boots going between the coil and plug and can weaken the coils over time. With the age and mileage of this weak ignition coils are possible and likely the boots are worn out.
Take a look in those spark plug tubes and see if you are getting oil in there.
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Tom Greenleaf
Ultimate Carjunky
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Dec 20, 2013, 8:24 AM
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Re: Leaky Valve Cover Gasket = Bad Gas Mileage?
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Leaking gasket probably not involved but should be tended to especially if soaking spark plug boots.
Gas mileage??: It's generally measured how far you went on how many gallons taken know full to known full and do the math. If you just watch fuel gauge and get gas there tons of room for errors. A Civic if just one gallon off when you get more fuel makes a lot of difference. That and as you mentioned fuel formula, % of ethanol and plain cold (if the case) can use a good bit more alone all depending on many factors.
Not sure yet MPG is really an issue at all with this,
T
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DanD
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Dec 20, 2013, 9:00 AM
Post #6 of 6
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Re: Leaky Valve Cover Gasket = Bad Gas Mileage?
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As everyone else here has said; winter's cold temperatures will use up extra fuel.
I know you went in and had the vehicle checked; but because there were no running issues for them to latch onto, a few small things could have been overlooked.
Thermostat for one; if it is not holding the engine temperature in the proper temperature range, will cause fuel mileage loss.The computer knows that a cold engine needs more fuel to run properly.
Coolant temperature sensor; it may be sending a signal out that is within its range, not to trip a code; but it should be checked for accuracy. Again if the computer things the engine is cold, it will dump more fuel.
There are many other things that could cause this loss of fuel mileage; but a scanner and someone that is willing to take the time to investigate the possibilities are what you need.
The dealership is likely a flat rate shop, meaning the techs only get paid while producing. If the guy that checked your vehicle didn't have any codes or drivablity (sp?) issues; it likely got the bums rush out the door, so he could go onto the next vehicle.
Dan.
Canadian "EH"
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