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F15 - The Fastest 1/4mile
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Discussion Starter #1
I swear that my VR4 is getting horrid gas mileage. Most folks say that the VR4 does pretty good. It seems to run fine, real strong... but maybe something is wrong. Any suggestions on what I can do to figure out if its a problem??
 

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You break em, we fix em
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Check the o2 sensors with a datalogger or voltmeter. Number one culprit of bad gas mileage. Reading should "cycle up and down between 0-1V at idle and while cruising.

usually they fail and read flat 0V, which the computer interprets as lean and continues to add fuel to no avail, resulting in your terrible mileage.


BTW, When you stomp on it the ECU doesn't use the O2 sensors, gos into open loop so it will run fine then.
 

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F15 - The Fastest 1/4mile
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913 Posts
Discussion Starter #3
Thanx Jim,
I have a voltmeter, where are the 02 sensors and how could I check them?
If they are bad do I just purchase new ones?
THANX!
 

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Lost Soul
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6,235 Posts
Does this same O2 sensor make your car smell like rotten eggs?
My car does this a few times a month. And I think changing plugs and wires......and making sure your airfilter is clean helps with mpg.


-Jeff
 

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How bad is your gas mileage? If its 16mpg or better I would worry about it. If it's worse just buy new O2 sensors and change them out. They run about $120 for a pair.
 

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Me to

I just bought my car ... last saturday .. and i have gone about 600 miles and gone through 3 tanks of gas
... maybe I should stop stomping it everywhere though ... hehe!:D
 

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BFA
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Try $190 a pair....

I was going to see about getting new ones, but that's a little too steep for me. My ARM-1 cycles at idle and at cruise, but it takes it some time to idle right, and it is usually running rich at idle if it's not cycling. Do the O2 sensors either operate normally, and then not at all, or can they be degraded and operate half-ass?
 

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1 slick Mothafu*ka
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2,287 Posts
SnakeSkinner said:
the rotten egs thing is from clogged cats most of the time
I've smelled that a few times while driving my car, how would I go about fixing that? It's a really unpleasant smell and i always blame the passanger because i know it wasn't me:D ;)
thanks.
 

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You break em, we fix em
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You can get the O2 sensors from ANY parts store that carries KEM electrical components. They are the correct sensor but come with only the leads, no connectors. they are under $50 apiece, well worth the extra effort to cut the connector off your old one and splice them in. Bosch and other companies don't make them for our cars, so you have to find a chain auto parts store that carries KEM. I got mine at Trak Auto.

16 MPG Trevor are you CRAZY! My 15G modified car gets 22 MPG OR BETTER, 25 or so on the highway. If your getting anything under 20 you have problems and/or your car is not tuned properly.

To check the O2 sensors, measure resistance across terminals 2 and 4 on the sensor, should be around 20 ohms at 68 degrees F. Then jumper terminal 2 to the battery positve, number 4 to the battery negative. Now run the car and measure voltage across terminals 1 and 3 should see 0-1V cycling around as the car idles. Check both sensors, my guess is one or both will read 0V = not working.

layout of connector is:

tab on top
1 - red wire 2 - black wire
3 - black wire 4 - white wire
 

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BFA
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SO if my air/fuel guage cycles, this would be th same thing as teting them?

My AF gauge cycles at Idle, but it has to sit for a minute sometimes. Wold this be a problem with the O2 sensors?
 

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It must be the way I drive then. ;) Out of the three stock TT 3/S's I've owned they've all got between 16.7 and 18.7mpg around town. My Stealth still gets the same gas mileage that I got out of it when it was stock (17-18).

EPA mileage estimates for TT 3/S's is 18mpg city and 24mpg highway.
 

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You break em, we fix em
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I do drive mostly highway probably 80%.Part of the good thing about modding the car is that with a better flowing intake and exhaust, ability to adjust fuel curve, etc. you shoudl eb able to get better MPG as well as more power.
 
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