Electrical - So, I installed an Amp/Sub, and now my idle is rough?? | Ford Escort Owners Association (FEOA)
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Electrical So, I installed an Amp/Sub, and now my idle is rough??

Discussion in '2nd Gen 1991-1996 1.8L DOHC' started by adidas4myfeet, Apr 13, 2016.

  1. adidas4myfeet

    adidas4myfeet FEOA Member

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    Hi. So I got a 95 Escort the other day. Freebie!! It was running nearly perfect, and I'm a bass guy, gotta have it. So I installed my sub and amp. Nothing crazy. Single 10" with a Rockford amp. 8guage wiring kit. I've done the same thing in just about every car I've ever owned.

    The very first drive afterwards, the idle was pretty rough, and it's stayed that way.

    Not too sure where to start?
  2. dchawk81

    dchawk81 FEOA Member

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    You need a more powerful alternator.
    adidas4myfeet likes this.
  3. adidas4myfeet

    adidas4myfeet FEOA Member

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    So, when I test the alternator in a little while, and it's in the range, it's probably going to read normal(just a guess, as it's never had an issue), but I need one that will more than likely test better than normal? Maybe in the 15 to 16 volts range? As apposed to 13 to 15 volts?

    Thanks!
  4. adidas4myfeet

    adidas4myfeet FEOA Member

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    So the batter was at 12.86V with the car off, and 14.7v with the car running. Is that still sounding like I need a better alternator? (Thank God alternators are pretty cheap and easy)
  5. Pizzaman5000

    Pizzaman5000 FEOA Donator

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    Wait wait wait, you unplugged the battery. It is quite possible that your power usage is causing the rough idle, but when you unplug the battery, the computer is going to be testing every system slowly to figure out what is different. You could have some slight vacuum leaks, blah blah blah.

    I'm not down playing the current draw, I'm just saying that simply unplugging the battery for 15+ minutes will clear a lot of semivital memory. Like make the injectors stay on 5% longer, or the MAF is inaccurate by (x) %.

    I'm no expert on batteries, but lately have read quite a bit on them. Most high output alternators put out the power at lower RPMs, that's about it. Many high output alternators are designed for AGM batteries, which have a different charge current, so do a little research on bulk charge and float charge rates. Otherwise you're gonna be buying batteries every year.

    A useful bit of info. Watts= amps times volts. 10a @12v= 120w. Honestly, our alternators putting out 80amps? I'd go for a second battery, or a capacitor before an alternator but after cleaning/making better every ground location on the chassis. That system shouldn't draw more than half of the alternators MAX output.
    My concern is that a larger alternator will put too much current into the battery and make it get too hot.
  6. ShakeZilla19

    ShakeZilla19 My name is ^^^

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    Seems a bit odd. I have 2 amps, with 2x10" subs and a pair of 6x9's. Im using the stock alt and an UDP. I have no charging issues except at idle.

    How old is the battery? Your voltages seem good, so it sounds like the alt is fine. Can you confirm that powering your sub is in fact causing the engine to run rough? IE disconnect your amp and see what happens. Could have just bumped something while installing your gear.

    Check your negative side battery cable, that connection at the battery is notorious for getting corrosion.
  7. dchawk81

    dchawk81 FEOA Member

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    People doing car audio have always had to buy "bigger" alternators when their system pulled too much current. That's why I suggested it. Most stock alternators are just good enough for what's in the car from the factory.
  8. Intuit

    Intuit FEOA Member

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    600 RMS on a dual-coiled 10" wired to 2 ohms and haven't ever done anything other than stock alternator.

    If you pull the fuses on your modifications you'll probably still find that you have a rough idle. However, I'm not saying that this is a coincidence.

    As Shake pointed out, you did disturb grounding. "Voltage drop test" from chassis to battery post negative. Google the quoted text for more detail, or just ask. You'll want to peak the electrical loads running high-beams, rear defrost, front defrost on high fan, brake lights running, hazard lights, stereo cranked, RPMs about 3.5-4.0k, engine fan running, etcetera during the test. It's possible to relay the engine fan on high but don't bother going that far.

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