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Old 06-17-2007, 10:53 PM   #1
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Default Gas Mileage Concerns

Hello everyone,
You all helped me with my ailing 1994 Park Avenue that runs great now thank you! However, every now and again I'm getting the 18X signal failure code; only at start up and if I turn the car off and start it again it isn't current. I wonder if this doesn't contribute to my wierd gas mileage. My Park Ave. with the 3800 series is getting 28-30 highway and 18-20 around town. It seems like a huge difference to me and was wondering if something was causing this? My 1994 9C1 driving the exact same routes gets 19-22 highway and 15-18 around town. Thoughts?
Thanks, Bryan
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Old 06-18-2007, 12:18 AM   #2
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I believe the code you are referring to comes from the crankshaft positioning sensor. If it is not a hard code I would say that somewhere along the circuit there is a fault. Check the circuit first then check the sensor itself. Through research (not quoting this) you would also be recieving a 3x signal code if the sensor was bad.
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Old 06-18-2007, 10:31 AM   #3
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I'm not 100% sure we can say the 18X might be missing and the 3X should automatically be missing. This sensor contains two paths for the signals..it'* possible one is bad and the other is still functioning. Unless the +5V is missing from both.

The mileage sounds on the mark to me. Mileage depends on your city driving. A person living in NYC is going to get poor mileage while someone in Enfield CT (both being cities) will get much better mileage.
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Old 06-18-2007, 02:10 PM   #4
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OK thanks guys,
I guess the gas is nothing to worry about and I'll troubleshoot the crank sensor. When I start the car up and the light comes on the car shifts a little different than when the code is not present. I tested this when the light was on the car was shifting at higher than normal RPMs and rougher than ussual. I put it in neutral shut it off, started it again and no light and no odd shifting. The code only seems to occur if I get in and start the car immediately; if I get in and wait like 1 or 2 seconds it doesn't come on.
Thanks, Bryan
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Old 06-18-2007, 07:08 PM   #5
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Thats really freaky..

Have you had any other codes?

The crank sensors are cheap enough... Might be worth the replacement... And getting 30 Mpg on a Park Ave is not bad at all

Also depends on your gear ratio

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