[89greenstang]

i have a 89 mustang lx 5.0 with AOD trans right now i get about 9mpg city the cars got 150,000 miles on it its got new air filter fuel filter spark plugs and wires i was wondering what else i should check?

[NFChaos2003]

How's the performance? Does it drive ok? Have you checked for codes yet?

[89greenstang]

the performance sucks too it drives fine but a occasional miss fire and i pulled codes and it said something about a heater circut open

[ryanw]

check your codes, it maybe time for new O2 sensors, perhaps there's some thing wrong with your EGR...

[dr.gonzo!]

Originally Posted by 89greenstang i have a 89 mustang lx 5.0 with AOD trans right now i get about 9mpg city the cars got 150,000 miles on it its got new air filter fuel filter spark plugs and wires i was wondering what else i should check?

EDIT:^^^^ beat me to it.


New oxygen sensors? I have an 88 AOD that gets about 170 miles on a tank and takes 11 gallons when I fuel up.

170/11 is ~ 15.45 mpg and I drive mostly highway and conservative. It would be cake to get 9mpg with a heavy foot in the city with my car.


Not sure on the miss fire. Timing? Correct ignition sequence? Vacuum leak?

[ryanw]

^^ i thought we had a 15 gallon tank

[89greenstang]

i never thought of doin new o2 sensors but i also smoke tested the vaccum system

[recore]

I've got the same set up, 89 GT with AOD and daily driving I get 16 mpg average, driving like a monk. Plus my car is lowered so that's an extra mpg.

[dr.gonzo!]

Originally Posted by ryanw ^^ i thought we had a 15 gallon tank

We do, but if I drove on all 15 gallons I would be stranded

It's also easier on the pump not to take it to the extreme. To see how many mpg you are getting, fill up on gas and see how many gallons it takes then get in the car and read the trip OD then miles ÷ gallons. For me its ~ 170 ÷ 11 = 15.4545 mpg. This is assuming that you reset the trip od every time you fill up on gas. Most people don't but its something I OCD on

Originally Posted by recore I've got the same set up, 89 GT with AOD and daily driving I get 16 mpg average, driving like a monk. Plus my car is lowered so that's an extra mpg.

Mine is lowered too

[89greenstang]

thats a really nice looking stang i like the white with the smoked headlights look

[The Novice]

Also how long has this problem been going on? like said before def. check codes first. Does it do anything else? any other symptoms? Bogging, sputtering, rough idle, anything else?

[89greenstang]

its been going on ever scince i got the car but also usually whenever i come off from a stop it misses and act like its gonna bogg out.

[The Novice]

Originally Posted by 89greenstang its been going on ever scince i got the car but also usually whenever i come off from a stop it misses and act like its gonna bogg out.

Well hopefully its just your O2 sensors then. Take a look a those like said before.

[89greenstang]

yea but how would you know if there bad or not?

[The Novice]

Originally Posted by 89greenstang yea but how would you know if there bad or not?

Check codes, signs of bad/rough idle, surging, and bad gas mileage. I would be leaning towards thats the issue. At least check and make sure they arnt the originals, i dont know how long you have had the car but if it has been doing it the whole time you have had the car like you said, and your gas mileage is suffering greatly i would recommend changing them anyways. I think they run roughly $40 bucks a peice. but with gas $4+ a gal and you only getting about 6 mpg, id say the saved gas should pay for itself in a couple fill ups.

[FastStang91Lx]

Do a compression and leak down test. Your motor just might be tired and ready for a rebuild.

[Frankenstank]

If it has been a while since u changed the o2 then just go ahead and change it they get lazy after a while.

If you had an O-scope you could hok it on the sensor and watch the change in voltage when it goes from rich to lean. The scope can be a little pricy though.

Or get a a/f guage so you can see the change from rich to lean but you ussualy will have to buy another o2 sensor to dedicate to the guage.

So I would recomend if there are not any codes for the engine then go ahead and replace the o2 as it may have become sluggish

[88BlackPonyGT]

If it has the catalytic converters, have them checked.

[88BlackPonyGT]

Check the o2 sensor wiring also. The open heater circuit code usually indicates a bad sensor. If your catalytic converters have 150,000 mile,chance are they are clogged.

Here is a trick:
Remove your upstream o2 sensors and take it for a drive. If you noticed an enormous increase in performance, you probably have clogged cats.

[FastStang91Lx]

Originally Posted by 88BlackPonyGT Here is a trick: Remove your upstream o2 sensors and take it for a drive. If you noticed an enormous increase in performance, you probably have clogged cats.

Don't work that way. We only have one set of o2's. If you remove them, it goes into 'safe' mode.