need help with gas milage...!!! help

Well, def plugs and wires are a good start for any car. I got 17.8 mpg on a highway trip in my 91 with 500 rwhp and 3.73 gears, so its def poss to reach 20 or more highway with numerically lower gears.

I hate to tell you this, but if you are not mechanically inclined, you bought the wrong car. A 22 year old car is a little like a 62 year old woman - both are old enough to collect social security and have more than their share of aches and pains. Be preapared to buy some tools and learn some good mechincal skills. If you don't you will go broke paying for someone else to fix the car.

Dump the codes first and if you don't find any, it's time for a tune up - new spark plugs, cap, rotor, wires, fuel filter, oil change, and a new air filter.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 3-Jun-2011. Removed the link to BATAuto.com and troublecodes.net instructions on codes and how to dump them. Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.





If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.
Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

find out what it has for rear gears and you don't mention if it is stock, mild mods or what it has. A filthy air filter will hurt but also a many things will factor in. 1st run a KOEO test and see if you have any codes stored and address those, check for vacuum leaks and give it a good tune up. check tire pressures. also ckeck the timing to see if PO bumped it up. with high mileage it's really hard to figure how well it was taken care of, carbon build up etc. you might be limited. If you don't have one get an OBD 1 tester and do the test, codes can have a bad effect, then go from there.

i have a similar problem..i have full exhuast and cold air intake and 3.27's and im lucky if i get 200 miles out of a tank..and ive done evry test in the book..so i just except it

I just completed a 2600-mile trip in my Saleen with 3.55 gears and averaged just under 24 mpg through 90-100 degree heat with the AC on and 75-80 mph speeds.

"Key on, engine off" as opposed to KOER or "Key on, engine running".

Half a tank in 20 km is beyond bad gas mileage. No matter how bad it may be running, there is no way that much fuel could be going through the engine, even if you were racing it. Have you ruled out a faulty gauge or a fuel leak?