Crappy gas mileage but no check engine light.

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SmockDoiley

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Jun 14, 2003

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San Diego, CA

Mar 2, 2004

#1

• Mar 2, 2004

• #1

My wife keeps complaining that the 95 gets horrendous gas mileage; like 10mph. There are no engine lights on, and the car runs strong. Also, the engine looks really clean, the air filter is spotless, the plugs look new, the distributor cap and rotor are good. I think when I get out there, I'll check the timing, change the plugs, PCV, o2 sensors, and stock H-pipe since I have a new one laying around. I cant think what else would cause bad mileage besides obvious things like crappy engine or tranny and stuff. The car is bone stock with 102k miles on it.All the fluids are fresh and I think the car may have sat for along time because all the tires were new but dry rotted and bad, and the mileage was fairly low,98k, for a 95. Anything else I may be forgetting or you would suggest. I'm more a carbed guy so I'm not as well versed with EFI, but I'm a good mechanic. Also she is in illinois right now and Im in san diego. Any other valves or sensors that could cause bad mileage like EGR junk. Thanks for you help, she loves the car but I'm sick of her complaining every day about the mileage. Not much I can do about it out here. Anybody around Chicago that can shoot codes? Shes pretty hot and very sweet!!

 

Michael Yount

Mustang Master

Apr 10, 2002

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79

Charlotte, NC

Mar 2, 2004

#2

• Mar 2, 2004

• #2

Most AutoZones can pull the codes for you for free. But it's pretty easy to do if you think you'll be in the business of doing other work on the car; Walmart sells the scanners for less than $25. The diagnostic port is connected to the wiring harness behind the driver's side strut tower, and the scanner will have instructions with it for how to pull the codes. I'd definitely pull them before I started changing parts -- although if the O2's are original - it's time for new ones. Is it possible that the check engine light is coming on from time to time (not staying on) and she's not noticing it? Many times the light will occur that way when it's O2 sensor related. In any event, the diagnostics should store a code. Good luck with it.

 

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SmockDoiley

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Jun 14, 2003

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Mar 2, 2004

#3

• Mar 2, 2004

• #3

Thanks. So nobody has any advice on what else can cause bad mileage? I guess this is the only mustang that gets bad mileage.

 

Michael Yount

Mustang Master

Apr 10, 2002

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79

Charlotte, NC

Mar 2, 2004

#4

• Mar 2, 2004

• #4

I remember you posted before about her mileage on the trip (I think). Actually, if she's in heavy stop and go traffic - 10 mpg is not beyond the realm of reason. But if her city driving has less stop and go, I think it ought to get better than that too. 15 or so in town and 20 or so on the highway ought to be reasonable. Let us know what you find out.

 

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SmockDoiley

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Jun 14, 2003

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Mar 2, 2004

#5

• Mar 2, 2004

• #5

no stop and go traffic in rural illinois. Even if it was, it shouldnt equate to that crappy mileage.

 

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SmockDoiley

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Jun 14, 2003

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San Diego, CA

Mar 2, 2004

#6

• Mar 2, 2004

• #6

she said shes getting 100-150 miles per tank. Thats horrible

 

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SmockDoiley

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Jun 14, 2003

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Mar 3, 2004

#7

• Mar 3, 2004

• #7

nobody?

 

LX302

Stanger

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Feb 29, 2000

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Bethlehem PA

Mar 3, 2004

#8

• Mar 3, 2004

• #8

Are you sure she's calculating it correctly? Exactly how much gas goes in check the odometer, and the miles driven, then calculate, or is she calculating just by the tank full?
Not saying your not doing it correctly, just asking the question to eliminate the possibility everything is fine and it's just a math error..

 

9

92Patrol5.0

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Sep 20, 1999

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Cedar Rapids, Iowa

Mar 3, 2004

#9

• Mar 3, 2004

• #9

Has anyone mentioned fuel filter? If that hasn't been changed, 102k on the fuel filter would probably cause it to clog up a bit. This can eat your fuel also. Something cheap and easy to replace. Might not be the culprit but can't hurt to change it.

 

Michael Yount

Mustang Master

Apr 10, 2002

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79

Charlotte, NC

Mar 3, 2004

#10

• Mar 3, 2004

• #10

Smock - seems like we went through this before on the long trip mileage, so at the risk of pissing you off I'll ask again. Do you have specific and correctly calculated mileages? 100 - 150 miles per tank is a HUGE difference in potential mileages. Just for example - 12 gals. on a 100 miles is about 8.5 mpg - crappy mileage for sure. 9 gals. on a 150 miles is almost 17 mpg - perfectly acceptable around town mileage for a heavier 5.0. So, what exactly is the gas mileage she's getting? Also - have tires/gears been changed - are you sure the odometer is accurate?

 

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SmockDoiley

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Jun 14, 2003

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Mar 3, 2004

#11

• Mar 3, 2004

• #11

I dont think it takes much calculating to see the kinda bad mileage she is seeing. In any car, when you lose 50% of your mileage its pretty noticable. Honestly, the last time I posted about this when she was driving across country nobody could give me any real trouble shooting or ideas. Everybody just thought she was calculating things wrong. I'm not trying to step on any toes, but its getting a little old, and I cant believe I'm the only person on Stangnet that has seen bad mileage on a mustang. Its kinda insulting when you report 8-11 mpg on a car thats suppose to get around 16-22, and the only thing people can say is that you never took math in high school. Again, im not trying to be a jerk, its just that nobody seems to believe the numbers or something. I dont see how youd get worse mileage by having a clogged filter, plus wouldnt that cause it to run poorly or hard start.

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Mar 3, 2004

#12

• Mar 3, 2004

• #12

Like I said - at the risk of pissing you off.....

No disrespect intended - it just seems that you're estimating what is a very simple calculation to perform. In any event - I think you have gotten some input, but haven't been able to act on it as the car's half way across the country. Rather than have us guess at it (which is what you're doing) you need to pull the codes or have them pulled first. My guess is that it will tell you you've got a problem with the O2 sensors and/or clogged cats if they're still on the car. Like you, I doubt it's a fuel filter problem as there are usually drivability issues associated with that. Good luck with it.

 

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SmockDoiley

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Jun 14, 2003

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San Diego, CA

Mar 3, 2004

#13

• Mar 3, 2004

• #13

First off, I cant count on any woman to sit there with a calculator and written down mileage every time she gets gas. An ordinary man would do this because well thats what we do. I'd be able to tell you in a heart beat if it was my car what the exact mileage is down to the hundredth of a mile. But with her, its like pulling teeth to get exact numbers. But when she drives 40 miles a day, and fills up at least 2 times a week, thats bad. And its highway driving to and from work. Personally, anything under 15 mpg on the highway with a mid to newer 90's car is crap. And we can already establish that best case scenario the car is getting 12 mpg. I understand your point, but we dont have to be precise with mileage to pin point the problem. My buddy has a 94 Trans Am. Its really clean, and he drives like Jesus was riding bitch, but the darn thing wont get better than 8 mpg. We just cant figure it out. I see the same thing happening with this thing. The few times I drove it, I could tell the thing couldnt be getting more than 12 cause the tank would be dry after every night we'd go out. Other than that, its great. I have a spare H-pipe and the cats only have 16k on them, I'll try that with new O2 sensors. If that doesnt do it, I guess I'll have to keep trying. If the code checker is only 25 bones, Ill invest in one and check it out. In the meantime Im having her switch to regular to save money. Also, I'll be switching to a KN air filter, and changing the plugs. I'll check the timing too, and look for vacuum leaks or bad pcv valve. Could the EGR give bad mileage?

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Mar 3, 2004

#14

• Mar 3, 2004

• #14

Remember - if AutoZone is in the area - they've always pulled them for free when I ask; I've seen many others do the same thing. I'd invest in that request before I started changing parts randomly. Yes, if the egr is malfunctioning, it can impact both drivability and mileage - it helps fuel mileage by cooling the chamber charge and allowing the computer to add more timing. Of course, that should generate a code and usually a check engine light. And remember, codes can be stored without a check engine light illuminating.

By the way, my wife proudly reports her gas mileage to me (I really don't care); of course she gets it by pushing the trip computer button on her Bimmer.

 

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SmockDoiley

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Jun 14, 2003

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San Diego, CA

Mar 3, 2004

#15

• Mar 3, 2004

• #15

See, thats cheating, lol!! I wanted to change the pipes anyways and the O2 since I dont know how old the stuff is, and I got this good stuff laying around. The other stuff is just standard cheap stuff anyways. I really want to just go through the car so I know it was done right and its all new. Not sure how close a name brand parts store is to her, but Ill have her look.

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Mar 4, 2004

#16

• Mar 4, 2004

• #16

Did a little more research in my Probst book about fuel economy. Apparently another problem that can occur is clogged injectors. They don't all clog at the same time - one clogs first. As it does, that cylinder goes lean. The O2 sensor - which is reading 4 cylinders combined - sees the lean condition, and enriches the mixture making the other 3 cylinders too rich, and causing more fuel use. According to Probst, the symptoms are a rough idle, you won't pass emissions, and the car can use as much as 25% more fuel. When you pull the plugs if one or two look white, but the rest look much darker, the white ones are likely from a clogged or malfunctioning injector. Another way to test for which injector might be contributing is to disconnect the iab solenoid, with a shop tach attached, one at a time begin disconnecting the injector harness connector. As you disconnect one, the rpm should drop by about 100. If it doesn't drop, something is either wrong with that injector, or the connector or the harness.

More food for thought.

 

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SmockDoiley

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Jun 14, 2003

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San Diego, CA

Mar 4, 2004

#17

• Mar 4, 2004

• #17

Very interesting, good research man. I'll check that out when peaking at the plugs.

 

bmorrisj

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Sep 26, 2003

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Mar 4, 2004

#18

• Mar 4, 2004

• #18

i think i should be doing that too, im getting the same symptoms....