Virrdog Posted October 9, 2007 Share Posted October 9, 2007 Dude, get real mileage readings. Ignore the gauge. Seriously. Miles traveled / number of gallons consumed. Do that for at least 500 miles. And if you car is magically losing gas it might be the tank has a leak. Something to check. Check the following: Spark plugs Spark plug wires O2 Sensor / Wiring PCV Vavle Fuel filter Air filter Vacuum lines Replace all of them except for the 02 sensor if you have done it recently. I would definitely get rid of the cheap spark plug wires, though. Get some NGK's silicone wires. If your car coolant temperature sensor is bad it will tell the car to run rich to warm up constantly and consume lots of gas running real rich. Quote Link to comment Share on other sites More sharing options...
Cougar Posted October 9, 2007 Share Posted October 9, 2007 If the O2 sensor has less than 40k miles on it then I would tend to say it is probably ok. It might be best to take the car in to a shop that can do an exhaust gas analysis and see what it shows. The MAF sensor may be causing this but I would want to be sure of that before replacing it due to the cost of a new one. This problem seems strange since you state it runs well. I would think that with gas mileage as poor as you state the engine would not be running smoothly. The problem looks more like there is a gas leak somewhere than a engine problem. Quote Link to comment Share on other sites More sharing options...
Suzam Posted October 9, 2007 Share Posted October 9, 2007 This problem seems strange since you state it runs well. I would think that with gas mileage as poor as you state the engine would not be running smoothly. The problem looks more like there is a gas leak somewhere than a engine problem. Cougar brings up a good point. Do you smell gasoline vapors? How about your exhaust, does it smell rich or different in some way? (please don't suck in too many fumes! Carbon Monoxide is poisonous!) Quote Link to comment Share on other sites More sharing options...
ericem Posted October 9, 2007 Share Posted October 9, 2007 A o2 sensor can make performance worse correct? Quote Link to comment Share on other sites More sharing options...
Manarius Posted October 9, 2007 Share Posted October 9, 2007 A o2 sensor can make performance worse correct?Yes, but it's distinctly noticeable. You know, your tank holds 15.9 gallons - 12 gallons gone is not empty. Your gauge lies. Like others have said, go over 500 miles and tell us the overall miles per gallon. From there, we can decide what's going on. Quote Link to comment Share on other sites More sharing options...
ericem Posted October 9, 2007 Share Posted October 9, 2007 over 500miles Quote Link to comment Share on other sites More sharing options...
Manarius Posted October 10, 2007 Share Posted October 10, 2007 over 500miles 500 miles will allow for at least one tank if not two - so we can get some consistency among the mpg ratings. You should never base your findings on one sample. Having many samples and being able to provide an average is important. Quote Link to comment Share on other sites More sharing options...
nipper Posted October 10, 2007 Share Posted October 10, 2007 500 miles will allow for at least one tank if not two - so we can get some consistency among the mpg ratings. You should never base your findings on one sample. Having many samples and being able to provide an average is important. Recomendation is three tanks of gas, but two will do (anything in engineering is done in at least a set of three). nipper Quote Link to comment Share on other sites More sharing options...
ericem Posted October 10, 2007 Share Posted October 10, 2007 500 miles will allow for at least one tank if not two - so we can get some consistency among the mpg ratings. You should never base your findings on one sample. Having many samples and being able to provide an average is important. Oh i thought you were asking him to drive 500miles on a full tank to see if it runs out of fuel. Quote Link to comment Share on other sites More sharing options...
jcniest5 Posted October 10, 2007 Author Share Posted October 10, 2007 Yes, but it's distinctly noticeable. You know, your tank holds 15.9 gallons - 12 gallons gone is not empty. Your gauge lies. Like others have said, go over 500 miles and tell us the overall miles per gallon. From there, we can decide what's going on. From memory, I believe my tank only holds 12 gallons, not 15.9. Just an update: I replaced the OS2 today with an OEM type 3 BMD, which has the connector (without me having to hardwire like my last one, which I could have done it wrong). The gas gauge seems to move just as fast. I have yet to test the MAF. And no, the gas tank doesn't seem to leak. There is no smell of gas anywhere, although the exhaust seems to have a stronger (richer) smell. It has always been like that, though. I'm going on a long trip, so hopefully this will help me determine if there is anything wrong with my car or not. I seem to be chasing a ghost (like someone posted earlier). Quote Link to comment Share on other sites More sharing options...
nipper Posted October 10, 2007 Share Posted October 10, 2007 From memory, I believe my tank only holds 12 gallons, not 15.9. Just an update: I replaced the OS2 today with an OEM type 3 BMD, which has the connector (without me having to hardwire like my last one, which I could have done it wrong). The gas gauge seems to move just as fast. I have yet to test the MAF. And no, the gas tank doesn't seem to leak. There is no smell of gas anywhere, although the exhaust seems to have a stronger (richer) smell. It has always been like that, though. I'm going on a long trip, so hopefully this will help me determine if there is anything wrong with my car or not. I seem to be chasing a ghost (like someone posted earlier). You have a 15.9 gallon tank. I want you to do this. Get a gallon gas jug and fill it up, put it in the car. Fill the gas tank. Drive the car untill the low fuel light comes on. Keep driving, but stay on secondary roads. Let the car run out of gas. Put in that one gallon of gas, then fill it up the rest of the way. You will see it will take 15gallons ish. This way we have you on sqaure one. You will know that you have a 15.9 gallon tank of gas. There is one possability, which i have never seen fail. The tank is split in two. Subaru uses a jet pump (Siphon) to move the gas from a to b .This never fails, but there is always a chance that your the first. nipper Quote Link to comment Share on other sites More sharing options...
Virrdog Posted October 10, 2007 Share Posted October 10, 2007 From memory, I believe my tank only holds 12 gallons, not 15.9. Believing does not make reality. It should be 15.9 unless someone installed the wrong tank at some point. The gas gauge seems to move just as fast. Please please PLEASE stop saying that! I thought this was covered enough times, gas gauges -when they are working correctly- are rough estimates of how much at a minimum is in your tank. the exhaust seems to have a stronger (richer) smell. That would definitely point to the CTS or possibly MAF and/or sticky injector (but less likely on the last 2 if its running good). Have you replaced the CTS, yet? Its only a couple of bucks and is usually bad... and would cause poor gas mileage. Hint Hint Hint... It has always been like that, though. Does that make it ok? You and logic don't seem to be bedfellows. Quote Link to comment Share on other sites More sharing options...
jcniest5 Posted October 10, 2007 Author Share Posted October 10, 2007 The CTS was just replaced a few days ago. The oxygen sensor was replaced Tuesday. I haven't touch the MAF sensor yet. I could get one from a junkyard, would that work? Or does that present too many possibilities of getting a bad MAF? But wouldn't a bad MAF trigger Check Engine light to come on? Same for the OS2? Okay, okay, I will stop saying about gas gauge moving too fast. Hehhehhe... Quote Link to comment Share on other sites More sharing options...
Virrdog Posted October 10, 2007 Share Posted October 10, 2007 I haven't touch the MAF sensor yet. I could get one from a junkyard, would that work? Or does that present too many possibilities of getting a bad MAF? But wouldn't a bad MAF trigger Check Engine light to come on? Try cleaning the MAF sensor element with some brake cleaner first. A starting to go bad MAF does not necessarily trigger the check engine light, it might just be dirty. Quote Link to comment Share on other sites More sharing options...
Suzam Posted October 10, 2007 Share Posted October 10, 2007 Okay, okay, I will stop saying about gas gauge moving too fast. Hehhehhe... Good thing you never drove the 1963 Chevy BelAir I had for a while. The fuel gauge bounced all over the place. Turn a corner hard or accelerate fast and it would swing toward E. Slam the brakes and it headed towards "F" then back down again. Quote Link to comment Share on other sites More sharing options...
jcniest5 Posted October 10, 2007 Author Share Posted October 10, 2007 Try cleaning the MAF sensor element with some brake cleaner first. A starting to go bad MAF does not necessarily trigger the check engine light, it might just be dirty. I am looking at the MAF sensor itself. It looks to be super clean, all shiny, not a build-up of any sort. Does anyone know the signal output of the terminals? The tech manual doesn't give any for the 90-94, just some earlier models. I see one that looks like mine, and I try to follow that, but it doesn't give any reading according to the tech manual. Here's what the tech manual says: 1) Unplug the MAF Sensor connector. 2) Measure the resistance between the MAF Sensor terminals and chassis ground (which, can't be done since this isn't grounded once unplugged!) 3) Terminals 1, 2 and 4 should have 1 mega-ohm of resistance to ground 4) Terminal 3 should have 0 Ohms to ground. Which one is 1, 2, 3, or 4? It has five terminals all together. Which one is the ground? According to a picture resembling mine but for the year 88-89, 1 is LgR=Burn off signal, 2 SA=Power supply, 3 and 4 is ground, and 5 is SA=Sonsor signal. What the heck are these? These can't correspeondent to the steps above. Can't be right... I'm very frustrated with this stupid tech manual. Quote Link to comment Share on other sites More sharing options...
Cougar Posted October 10, 2007 Share Posted October 10, 2007 By using your voltmeter you should be able to figure out what is what. The ground connections will be at zero volts with reference to ground. The power line will be about 12 volts. The signal line may vary between 2 to 5 volts but I'm not exactly sure on that one. I think that is a close estimate anyways. Quote Link to comment Share on other sites More sharing options...
jcniest5 Posted October 11, 2007 Author Share Posted October 11, 2007 Okay, I lied. I didn't go out of town to test the MPG for this aging Leggie. I went to the junkyard instead and got myself a MAF Sensor from a '92 Leggie. Also I got a MAP Sensor, which looks different than mine, but the connector is the same. Put both of them on and from driving to pick my kids at school, the car seems to be more responsive. Acceleration is quicker, seems to have a litle more pulling power, too. I'm gonna drive it for a few days and will post back. Thanks to all that reads this thread or offers inputs/hints/advice. Truly appreciate everything. Quote Link to comment Share on other sites More sharing options...
Sonicfrog Posted October 11, 2007 Share Posted October 11, 2007 The gas gauge lies! When I first got my 94 Leggy wagon Red running and on the road, I was bummed because I thought I was getting bad gas mileage too. But I later found that the fuel gauge shows empty long before I get to that point. On "E" I still have about four or five gallons left in the tank. The quick and dirty way to check mileage: Fill up gas tank to max. Reset tripmeter to "0". Drive until gauge is on "E". Refill gas tank to max. Divide the mileage on the trip meter by the amount of gallons you just put in. You may have already done this, but I just thought I'd post it JIK. Quote Link to comment Share on other sites More sharing options...
Olnick Posted October 12, 2007 Share Posted October 12, 2007 Divide the mileage on the trip meter by the amount of gallons you just put in. Absolutely the only way to do it. But does the OP even have a tripmeter if his speedometer went bad? Quote Link to comment Share on other sites More sharing options...
nipper Posted October 12, 2007 Share Posted October 12, 2007 Absolutely the only way to do it. But does the OP even have a tripmeter if his speedometer went bad? it can. With it being electronic they dont both work off the same drive anymore. The needle is a sepraqte circuit from the odometer. But like i siad, it depends why it failed. nipper Quote Link to comment Share on other sites More sharing options...
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