Tries To Die When Stopping.

Discussion in 'SN95 4.6L Mustang Tech' started by creektrack, Jul 3, 2013.

  1. 96 GT vert, 5 speed....

    When I'm heading towards a light and press in the clutch and hit the brakes it drops the RPM down to about 300-400 and then back up to normal, around seems as though it wants to die, obviously if I down shift it won't do it as I go through the gears, but I don't like down shifting all the time as it's a waste of gas...

    CEL did just come on today, so I will check shortly, but the car has a short ram intake with 80mm maf, brand new coil packs, and no exhaust after the h-pipe...

    Is this simply back pressure? Is it that big of a factor on this car? And if I slap some SLP loudmouths on there would it be sufficient? I honestly want my car as obnoxiously loud as possible while maintaining proper driveability....

    Sent from my SPH-L720 using Tapatalk 2
  2. Ive disconnected it and it alters the idle, so not sure how to fully diagnose a tps...

    Sent from my SPH-L720 using Tapatalk 2
  3. They don't always throw codes. And they can work on and off. Unless someone has another test procedure I say shoot up to the autoparts store and change it out if it works great if not return it
  4. I might have to try that out...

    Sent from my SPH-L720 using Tapatalk 2
  5. Pull the CEL code. That'll point right to the solution, or at least lead you down the right path.
  6. Don't waste time guessing. Have the code read. That's what it's there for
    jcgafford likes this.
  7. i agree. scan the codes before anything. but i bet it is the tps...
  8. Yeah imma head up to autozone here shortly...I really need to invest in a scanner..

    Sent from my SPH-L720 using Tapatalk 2
  9. So...the code was for the IAC, but the battery read bad, and to top it off, the motor developed a tic on the way home...

    Sent from my SPH-L720 using Tapatalk 2
  10. Man, you sound like me. I've been chasing gremlins for months on my car. Just today it developed a miss.
  11. If you can replicate the symptom while the vehicle is parked by revving it by hand and letting the throttle slap shut, try tapping on the IAC with the handle of a screw driver. If the tapping knocks the IAC loose and the idle improves, it would likely be your culprit. As far as the battery is concerned, my battery started fine one morning and I drove to the gas station. Once at the gas station my electrical system went berserk and left me stranded. It was as if someone flipped a switch and suddenly the battery was shot. Get a new battery before it screws you over.
  12. Im not even worried about about anything but the tick now...I think it spun a bearing...

    Sent from my SPH-L720 using Tapatalk 2
  13. So I figured out that the timing chain guides on the right side of the motor are whats causing the ticking sound...waiting on the parts to get in to fix the issue now...

    But quick question...if the battery showed up as bad when tested, would that cause the IAC to throw a code, or at the least cause the rpms to die down as im stopping?

    Sent from my SPH-L720 using Tapatalk 2
  14. bad/weak battery = poor alternator output.

    Poor alternator output = unstable/low voltage

    Unstable/low voltage = poor running motor (especially at idle).

    So...... A weak battery can make for a weak/no alternator output.

    Bottom line: Today's cars simply will not run right without a strong battery and charging system. IMO virtually all "strange" car symptoms should start out with a review of the battery/charging system. This goes DOUBLE for an electrical issue.
  15. Sounds mundane, but when was the last time the car had a tune up?

    About a year ago, my car was running like crap. Of course my mind, I started thinking about fuel pressure regulator, fuel pump, all these hard things. I gave it a full tune up (fuel filter, air filter, oil filter, oil change, coil packs, plugs, wires) and it was like waking the beast. All was fine. This is only my experience. Like others have said, check the charging system. It's quick and easy to get a report from Auto Zone or wherever else.
  16. Well I just bought the car maybe 3 months ago and have drivwn it maybe 100 miles...Supposedly the tune up was recently done, but I have no idea...I have although, done a full oil change and flush, replaced the coil packs with msd coils, replaced air and fuel filter, and replaced the alternator plug as well....along with a few other things...

    I took the car to autozone and the battery showed that it was bad, so it wouldnt let them check the alternator...this coming weekend when I change the timing set, I will be getting a new battery and plugs and wires as well...hopefully that will complete this vicious cycle...

    Sent from my SPH-L720 using Tapatalk 2
  17. Pull your IAC off, clean with carb cleaner, reinstall.

    A carboned up IAC is really common with EFI mustangs.
  18. Yes, good point. I also remember the hose going from my IAC to my intake was a little loose (not long enough) and outside air was seeping in through the small gap in between. I bought a longer length of hose and clipped it to just the right size and my idling quirks went away. Something else that's easy to inspect.
  19. The IAC is considered a non-servicable part. Sometimes cleaning it resolves it temporarily and in very rare cases, permanently. You're better off spending the money and replacing it.

    PDM Designers