Garbage gas mileage, 10mpg

Discussion in 'Fox 5.0 Mustang Tech' started by Grn92LX, Sep 12, 2004.


  1. Michael Yount

    Michael Yount Advanced Member

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    I don't think the elec fan/maf voltage is an issue - unless your battery/alt/charging circuit is having problems. The battery is there to provide the voltage the system needs when the alternator can't keep up due to electrical loads like big fans. Of course, over time, if the alternator isn't recharging the battery, that could cause other system problems - but you'd be having starting issues if that were the problem. If you suspect your alternator isn't keeping up, that's something that needs to be remedied - but I don't think it's causing your bad gas mileage.

    If it started after a swap from 24# injectors to a different maf calibration/30# injectors - I'd suspect the maf calibration.
  2. stangbear427

    stangbear427 Active Member

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    Don't suppose you still have the 24# squirts and a MAF calibrated for them to run a little experiment with, do you? Or did we already cover this somewhere in the last 5 pages... I'm not reading it all again, sorry
  3. Grn92LX

    Grn92LX Fidanza Man! Founding Member

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    I sold all my 24lb stuff a long time ago.

    My bad cold start idle started when the tremec tko went in. Today while I was under the car changing my oil, I noticed a sensor on the tailshaft of the tremec that wasn't connected. After some messing around I found the wire it connects to and plugged it in. Im wondering if that had anything to do with the bad idle issues after the tremec swap?

    I pulled the optomizer and it seems to cold start a little better but I have't tried it since plugging that sensor back in on the trans. Hopefully today if its not raining i'll try again and see how it cold starts.
  4. 5spd GT

    5spd GT "the 5.0 owns all" Founding Member

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    Have you ever mentioned it starting after the TKO install? That could have narrowed down some choices right there...so are you sure the guy didn't mess with your engine any? Trying to do some "tuning" of his own or something (cough cough...burn burn...cough cough)...sorry I brought back bad memories :)

    Yeah let us know in the morning if that connector was it or a part of the problem...I'm just trying to figure out what the "trans" has to do with a cold-start problem...?
  5. Grn92LX

    Grn92LX Fidanza Man! Founding Member

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    Thats what i trying to figure out too. Im sure the guy didn't do anything to the engine. He said he had to pull the longtubes to get the scattershield in (which is why I had asked how I know which o2 sensor goes to what harness) and he had to disconnect the battery to put the new starter in. Disconencting te battery for a few hours could have cleared out the KAM (keep alive memory) thus the bad idling? Or its possible that the disconnected sensor I plugged back in was an issue? I have no clue.
  6. Michael Yount

    Michael Yount Advanced Member

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    The only tranny connections should be for 1) back up lights - shouldn't impact idle; 2) neutral indicator switch and 3) VSS (vehicle speed sensor). Mine does not have 2 or 3 hooked up at all - doesn't seem to have any impact on my idle.
  7. Grn92LX

    Grn92LX Fidanza Man! Founding Member

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    I just tried starting it up dead cold (first start of the day) and it idles so much better!! All I did was put that sensor back in on the tranny. My friend looked it up and it's the neutral switch. How that has an effect on cold start idling, I have no clue. Removing the optomizer helped with cold starting a little also, but its much better now.

    Wonder if my mileage will improve now??
  8. Grn92LX

    Grn92LX Fidanza Man! Founding Member

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  9. Michael Yount

    Michael Yount Advanced Member

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    Could ambient temps have anything to do with this? It's been unseasonably warm down this way for the last week or so - while this threads been running. Warmer up there too? If so, I'd not get too excited til you see how it starts the first time it cools back off a bit. Just guessing at things....
  10. Grn92LX

    Grn92LX Fidanza Man! Founding Member

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    Its had this problem since the day the tremec was installed. I don't think temperature is totally at fault. It did idle worse when its cold out though before I plugged the neutral switch back in. Today its actually pretty warm for october. I just went and uncovered it and started it, it idled awesome with a slight surge for a few seconds then fixed itself and idled normal with NO help from me by giving it gas.

    How did that switch have that drastic an effect on my cold start idling? I wonder if that was hurting my mileage also? I think the optomizer was screwing my maf curve and hurting mileage too. I'll see how this tank of gas goes and more importantly, the one after this.

    Thanks for keeping up with my thread fella's, this thread has some really good info in it!

    Mike
  11. Jkstang78

    Jkstang78 Founding Member

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    Thanks for the creidt, Mike But I do have a name you :banana:
  12. Grn92LX

    Grn92LX Fidanza Man! Founding Member

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    I'm sorry, I should have said some dickbag looked it up for me :D

    J/K, thanks Jay


    :rlaugh:
  13. Jkstang78

    Jkstang78 Founding Member

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    THANKS MIKE :D & Your still a :banana:

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