I was wondering why my 88 mustang was getting such horrible gas mileage, I recently converted it to mass air, changed the plugs, wires, cap and rotor, air filter and fuel filter and I still only average about 13 mpg which is about 150 miles to a tank of gas. I was wondering if anyone had any insight into what the problem might be. Thanks
very poor gas mileage 88 stang 5.0
- Thread starter catman4115
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Euphoric306
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- Apr 5, 2004
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if its mostly city driving and short little trips that should be about right, thats what i average mostly
then again ive got gears and drive like a teenager hehe
might wanna try pulling codes, they might reveal bad o2's or something of the like
then again ive got gears and drive like a teenager hehe
might wanna try pulling codes, they might reveal bad o2's or something of the like
pull the codes and see whats up. Like mentioned above check your oxygen sensors.
How does the car idle?
Any vaccum leaks?
What is your base timing at?
What are the mods done to your car?
How does the car idle?
Any vaccum leaks?
What is your base timing at?
What are the mods done to your car?
Try running a diagnostic test on it, maybe some bad 02 sensors are causing a loss in mpg. Remeber, 87 and 88 had no check engine light, so you never know if somehthing is wrong until you do a test.
Another thing to think about- when my speedometer still worked correctly, I only got about 16 miles to the gallon on my 88. So 13 really isnt too far off. When I go on a trip or something with a lot of highway miles, i usually get about 22-25 mpg.+
Another thing to think about- when my speedometer still worked correctly, I only got about 16 miles to the gallon on my 88. So 13 really isnt too far off. When I go on a trip or something with a lot of highway miles, i usually get about 22-25 mpg.+
Jaswir
Member
the car has about 90k on it and the only mods i have are 3.73's, exhaust and a k&n filter. the car idels fine, when i rev it a little it doesnt drop the rpm's as quick as it did before i converted to mass air. my engine light isnt on but how do they check the codes on the older cars, cause i know on newer ones they have a diagnostic port? thanks guys
slo65
New Member
catman4115 said:
on my 88 the connection is on the driverside side, under neath the hood, kinda near the wiper motor, there's two connections, i bought a digital readout obd1 tool for the stang, pulled a couple smog related codes before, havent checked it lately
For a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.
I get 220-250 miles per tank, mixed commute driving. See my sig for mods that include a 3.55 rear gear.
I get 220-250 miles per tank, mixed commute driving. See my sig for mods that include a 3.55 rear gear.
I agree with jrichker, get a scanner first and check for codes. Yes you can do it with a analog volt meter, but it is easy to misread using that meathod. The idle failing to return quickly is a hanging idle. First I would clean out the TB and IAC and set the TPS to .98-.99 with the car at operating temprature, key on engine off. TPS can cause a lot of issues because if it is still reading that the throttle being open, it continues spraying the fuel injectors, while with the proper setting when you let off the gas such as coasting the injectors turn off and the EGR opens up, this can make a huge difference in gas milege. Also do a sweep on the TPS and be sure it has a smooth climb in voltage on the way from off to WOT, no dips or spikes should be detected.
As well as reseting this, try the ford idle reset procedure by disconnecting the IAC plug, setting the idle to where you want it to be (650-750rpm) and then turning it off, reconnecting the IAC, resetting the computer and seeing if that makes a difference. Fords are really bad when it comes to the IAC motor issues and a slow IAC will cause problems and usually doesn't shoot a code, not even on newer OBDII cars, let alone ancient EEC-IV. If your still getting hanging idle issues look for vaccume leaks, actually this should be one of the first things you check but if it isn't obvious then it could be comming form the intake manifold, I have scene a lot of cracked manifolds before and intake gaskets even more.
O2 sensors should cycle rich to lean two to five times per second. A bad O2 will either cycle slowly or the range will be short. It should cycle from .2 to .8 volts, .4-.5 volts as the middle mark. They also can cause MGP problems.
Are you running cats on your exaust? A clogged cat can back things up a lot as well.
As well as reseting this, try the ford idle reset procedure by disconnecting the IAC plug, setting the idle to where you want it to be (650-750rpm) and then turning it off, reconnecting the IAC, resetting the computer and seeing if that makes a difference. Fords are really bad when it comes to the IAC motor issues and a slow IAC will cause problems and usually doesn't shoot a code, not even on newer OBDII cars, let alone ancient EEC-IV. If your still getting hanging idle issues look for vaccume leaks, actually this should be one of the first things you check but if it isn't obvious then it could be comming form the intake manifold, I have scene a lot of cracked manifolds before and intake gaskets even more.
O2 sensors should cycle rich to lean two to five times per second. A bad O2 will either cycle slowly or the range will be short. It should cycle from .2 to .8 volts, .4-.5 volts as the middle mark. They also can cause MGP problems.
Are you running cats on your exaust? A clogged cat can back things up a lot as well.
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