Passat uses fuel when coasting in gear
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i thought that in newer vehicles the fuel was cut off when in gear and off the throttle and uses the momentum of the car to keep the engine turning over and as soon as fuel is supplied the power instantly comes back. maybe that technology is only in the newer models? if your car was at idle in your drive way it would burn fuel still, no? that has to happen for the engine to stay on.
Before it said on the car computer / mfd :
0l/100km no it never touches 0l/100km when i release the throttle?
The injectors should not operate if the throttle position switch is at idle, and the RPMs are above normal idle speed. My '99 sometimes has AM radio noise from the injectors when tuned between stations. You can hear the noise start when just barely opening the throttle while coasting in gear, and it gets louder as the throttle is opened.
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You must turn the engine off while coasting if you do not want it to use any fuel. 
& a nod.
If the engine is running, it is using fuel except for the period when the transmission is being used to "engine brake". In that case, you'll see "- - -" for the instantaneous fuel economy reading.
If the MFA is reading a different fuel consumption value than you are accustomed to (my 99 has done this), you probably need to clean the throttle body or possibly the crud from the PCV system.
& a nod.If the engine is running, it is using fuel except for the period when the transmission is being used to "engine brake". In that case, you'll see "- - -" for the instantaneous fuel economy reading.
If the MFA is reading a different fuel consumption value than you are accustomed to (my 99 has done this), you probably need to clean the throttle body or possibly the crud from the PCV system.
I've got a question for the panel concerning this cause I've recently noticed the same kind of deal as the OP. Before getting my GIAC chip the car would read " - - - " off throttle, and "200.0 mpg" with the clutch pushed in. After chip, off throttle I get a value in the 100's after a momentary " - - - ", and on the clutch it generally doesn't change from the value it was at before I pressed in the clutch. Additionally, I've noticed the average MPG meter changes a lot more. Anything with maybe an APR, GIAC, Revo, etc, chip that can chime in? I do still manage about 32 mpg on back roads (55 mph) and on highways (70 to 75 and depending upon hills etc.)
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auto2012, you need to clean the system as electron man stated.
if the engine is on and you are not on the throttle , the car is using very little or no gas at all because the transmission is keeping the motor in running. however if you are in neutral, the car must use fuel to keep the engine from stalling...which is why you should > double clutch and engine brake > more than > putting it in neutral to slow down .. that is, if fuel consumption is something you care about.
what im assuming, is that something is clogging the airflow.
if the engine is on and you are not on the throttle , the car is using very little or no gas at all because the transmission is keeping the motor in running. however if you are in neutral, the car must use fuel to keep the engine from stalling...which is why you should > double clutch and engine brake > more than > putting it in neutral to slow down .. that is, if fuel consumption is something you care about.
what im assuming, is that something is clogging the airflow.
The mpg calculator is a function of manifold vacuum. My guess would be that you are coasting in a higher gear now. If you down shift and raise the rpm's to coast, the vacuum will go up and then the display will go to ---. It only does that when you exceed 999 mpg since it can only display 3 digits.
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Coasting in gear should activate fuel-cutoff. As talked about above where the poster can detect the injectors not firing by using the AM radio to listen for the static. Vag-com measuring blocks can also show you when the fuel injectors stop firing. My 99 1.8t has a wide band air/fuel ratio gauge and I can see the AFR's max out beyond the lean limit of the gauge when coasting in gear and off the throttle.
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No MAP sensor on the 1.8t. Just a Charge Pressure Sensor on the SMIC (the wrong side of the throttle body to be able to take readings of manifold vacuum).
I would guess it calculates MPG from a combination of other inputs (MAF flow, Injector duty cycle, vehicle speed)?
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How is the engine supposed to stop using fuel unless it's off and not spinning? The fuel acts as a lubricant in the upper cylinder, so you don't want it to run too long without fuel. Which should obviously make people think about my transmission part issue....:hijacked:
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I know the injectors are off in gear with no throttle... but I have too always wondered how it doesn't run lean during this. Anyone know?
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Running lean is when you don't have enough fuel in the mixture to have the chemical reaction happen the way you want it to. You do have enough fuel for a reaction to take place, but not enough for the proper outcome. Fuel Cut Off is running with NO fuel, thus NO chemical reaction. It won't run lean because it isn't running at all. The cylinders act like those in an air compressor, just pumping air through the engine.
Fuel cut off is built into these cars from the factory. It helps improve gas mileage and reduce emissions.
Fuel cut off is built into these cars from the factory. It helps improve gas mileage and reduce emissions.
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Ok so they actually work like an air compressor sucking air through the vacuum system/creating vacuum while rotating, being driven by the momentum of the wheels>trans>crank. That's what I was leaning towards.
Yep.
Yep.
No, the gasoline does not act as a lubricant. Piston rings can scuff from lack of lube if overly wet with fuel. Some types of engines use a primer pump to start, for instance light aircraft, and can be damaged from excessive liquid fuel in the cylinders (but that's not a typical Passat issue).
i forgot to say that my car is chipped.
My car was chipped when i bought it, but i did not know that, so i went to my tuner and he tuned it with another software through the obd connection(you know where you put the vag com cabel in, its a b5.5 so it has a obd connection).
after the new software was installed, he did a TBA(throttle body alignment).
But all this happened after the car had been chipped, before that it always showed 0l/100km on the MFA when I "motor breaked" or coasted with gear. now it never shows that. look at my enclosed video, it shows what i mean.
ps: the fuel economy is has not decreased according to the MFA, but it just kills me that it doesnt show 0l/100km as it did before, i just want my car to be perfect you know.
http://db.tt/r42nRAI1
But what you are saying is that i need to clean my throttle body?
My car was chipped when i bought it, but i did not know that, so i went to my tuner and he tuned it with another software through the obd connection(you know where you put the vag com cabel in, its a b5.5 so it has a obd connection).
after the new software was installed, he did a TBA(throttle body alignment).
But all this happened after the car had been chipped, before that it always showed 0l/100km on the MFA when I "motor breaked" or coasted with gear. now it never shows that. look at my enclosed video, it shows what i mean.
ps: the fuel economy is has not decreased according to the MFA, but it just kills me that it doesnt show 0l/100km as it did before, i just want my car to be perfect you know.
http://db.tt/r42nRAI1
But what you are saying is that i need to clean my throttle body?
as you can se in the video it will never reach 0l/100km. im driving in third gear when i released the throttle.
and BEFORE my tuner installed the new chip ,which is perfect (the chip), the car did reach 0l/100km when i drove the car the same way on the video
and BEFORE my tuner installed the new chip ,which is perfect (the chip), the car did reach 0l/100km when i drove the car the same way on the video
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