Car Won't Start And Stay Running!!!!

Discussion in 'SN95 4.6L Mustang Tech' started by importrx7, Sep 18, 2006.

  1. I was at a buddys house tonight and went out to start my car and when i turned the key the car would turn on and then die right away. It would stay running if i gave it some gas and kept it above 1000 rpms. The car was cold, i kept it running by applying a lil gas to let it warm up and it still won't start and stay running.

    WTF is wrong with my car, seriously! It only has 54,000 miles on the car!!!

    Mods are BBK TB and Plenum, BBK CAI, and Magnaflow exhaust its not like its highly modified!!!

    Is it a PCV valve or something much worse???

    I need to get home but i don't know if i can keep it running to get me home.
  2. Typical Reply:

    Clean the IAC
  3. What and Where is that
  4. hmm well damn i wouldve thought some car smart ppl would chime in. I did a search and found this:

    Solving idle problems part 1 - Cleaning your IAC
    Does your idle rise and fall over and over again? Does your 'Stang stall when you come to a stop, or even when you put it in gear? Well if so then this series of articles if for you.
    In this age of fuel injection, idle problems can literally be caused by hundreds of different things. What this series of articles is aimed at is how to fix the most common idle problems found in the Mustang.
    The fuel injected Mustang uses a small motor/valve assembly that allows a specific amount of air to enter the engine to control it's idle. This valve is comonly called the idle motor, the IAC (idle air control) or the IAB (Idle air bypass). When your car is new the IAC works remarkably well. The problem arises when the car gets some miles on it (usually 75K+) and carbon fouling takes its toll.
    What happens is dirt, excess air filter oil, and most notably carbon gunks up the IAC valve and doesn't allow it to either open or close properly. This can cause an really high idle, a lumpy/surging idle or no idle at all. The solution is to either replace or clean the IAC. Obviously we are going to do the later and here is how.

    1. What is needed?
    - 8mm or 5/16 socket and ratchet
    - Can of Carburetor/throttle body cleaner

    2. Locating the IAC valve:
    Depending on the year of your Mustang the IAC can be in a few different locations.
    - On 5.0L Fox body cars the IAC is bolted to the side of the throttle body.
    - On SN-95 cars it is bolted to the intake manifold
    - On 4.6L DOHC and SOHC engines the IAC is located on the upper intake manifold.
    In reality once you know what one looks like (picture 2 "B" from a 94-95, fox body's have longer silver IACs) you should have no trouble finding yours. They all look basically the same except pre-94 cars were made of metal and are silver, 94-up cars are black plastic.
    icture 1

    3. Removing the IAC:
    This part, like the rest of the steps in this article, is simple. The IAC has an electrical plug that needs to be disconnected (picture 2 "C") Then all you have to do is remove the two 8mm-5/16" bolts (Picture 2 "A") that hold the IAC to the throttle body or intake. Watch out for the IAC motor to throttle body gasket, don't lose it!

    4. Cleaning:
    Next all you do is use the carb cleaner to clean the carbon out of both of the holes (picture 3 "C") in the IAC valve and both of the holes in the intake/throttle body.

    5. Putting it back together:
    Yet another self explanatory step. Put the IAC in place and install/tighten the 8mm bolts. Make sure you don't forget to reinstall the gasket.

    6. Fire her up!
    Finally you need to start the car and let it run for a few minutes to burn any leftover carb cleaner in the intake. You may have to crank the engine a little more than normal to start it for the first time and don't worry about the white puff of smoke you see coming from the exhaust because again it's just the carb cleaner.

    might want to check this out out also(Solving Idle Problems Part 3 and below that)

    Attached Files:

  5. I bet it is probably your IAC valve.
    If it has went bad get a OEM Motorcraft replacement IAC valve
    don't get a off brand.A IAC is one part I would never go cheap on.
    Also one or more of your fuel injectors could possibly be clogged.
    If that is the case have your fuel injectors cleaned by hand.
  6. [​IMG]

    You can get an IAC from Autozone, I've had the Wells brand one for over a year with no problems. Why would you spend the extra money for a motorcraft IAC when we all know that they suck and are prone to failure?
  7. Whata average price on a new IAC>
  8. Good tech Twista. :nice:

    If cleaning your IAC doesn't work it could be your crankshaft position sensor (CPS). Is it throwing a code? My Ranger was exhibiting the same symptoms and it turned out to be the CPS. Also try tapping on your IAC lightly with a screwdriver or something ... I've read that helps "un-stick" them sometimes.
  9. I've got the same situation with my car at the moment and I had the same problem on my 98 GT, so it's a common, easy to fix problem.

    After my car sits and cools down for awhile, it won't crank and stay on. Sometimes I can give it a little gas and keep the rpm's up and that will cause the IAC to work. Usually I will here a "thump" from inside the car when the IAC unsticks. If it doesn't unstick after a minute or so, I'll take a screwdriver or the short extension from a socket wrench and give it a light tap like DTNODYA recommended to help it unstick.

    I've seen prices of IAC's to run between $45 and $80.
  10. My mustang is doing the same thing now....and I just took my cougar off the road, and i'm screwed, '97 GTI did the exact same thing, but it was the TPS, throttle position sensor, from the read above, I guess it's unlikely??

    More likely the IAC? I can order both without pre-paying, from autozone, no special order, so should I order both and just take back whichever dont work....well wait no, if you install an electrical part you cant return it.

    My car did this twice before, but with a few more tries it would start, now, it simply wont. Of course if I put my foot on the gas and help it, it runs perfect, if I hold the gas just right, and once it's warm it's nearly driveable, but too annoying, and it's cold now, I Like to start it and walk away, and let it warm up, so.

    I'm going to follow the steps above to try and unstick the IAC, and if no luck i'll replace it. Then, if no luck, i'll replace the TPS since that's what I thought was wrong to begin with. They actually already ordered it and it's waiting to be picked I dunno what I should do....


    The engine is all stock except for a Roush CAI (Waste of money heh)