2003 Gt Engine Failure

Discussion in 'SN95 4.6L Mustang Tech' started by Jinx, Jun 22, 2013.

  1. Driving home yesterday and the engine just died. No warning, no sputtering. It may have bucked once or twice, and then nothing. All gauges were reading normal prior to the failure. No recent repairs or changes have been made. car has been consistent with it's MPG at about 23.

    I managed to coast to the side of the road and turn the ignition off. Then literally said "WTF" and turned the key and it started right back up (with some sputtering and a slight idle issue).
    I managed to get the rest of the way home and it just about die again as I was pulling into the driveway. It then lit up the red battery light and the SES light. I have a scanner, but not at home, so getting the codes may take some time today.

    The only possible things I can think of are:
    Busted vacuum line
    Failed fuel pump
    Failed alternator
    Failed COP
    Faulty sensor

    What say the rest of you??
  2. Just to speculate, but I'm gonna say the alternator went bad or the battery has a dead cell. Did the battery light come on before you turned it off at home?
    Jinx likes this.

  3. No, The battery light came on after the engine shut down. Like when you turn the ignition key to the on position, but do not crank the engine.
  4. Test the voltage at the battery and if you can get it started also test the voltage from the alt. I doubt that's the issue but who knows. Check the ground wire because Fords are great for eating them. Look at the battery terminal connections for any sign of green coming out of the wire. If so, replace the wire.

    I don't think that's your issue though. I think your crank sensor is dead. If the car starts just fine when cold but dies after it gets ANY heat in it then that senor is usually at fault.

    Also when the engine died were you moving or at a stop or crawling in traffic or what? Is the car a stick or auto? When is the last time the fuel filter was changed? What mods does the car have? How many miles? Do you properly maintain it?
    Jinx likes this.
  5. The car is a manual transmission, and I was moving at 55 mph when it died. All the electrical components continued to work after the engine stopped. I just put the code reader on it and no codes were available. So on a hunch, I looked at the rubber tubing at the IAC valve and sure enough I saw the damn thing collapsing with every engine surge and I could hear it hissing. Now I replaced this tubing a little over a year ago, however I could not find an OEM part so I replaced it with a reinforced gas resistant tubing. I'm guessing that the tubing has gone soft already and is not able to withstand the vacuum pressure. When I completely disconnect it and try to start the car, it will not continue to stay running. I have another thread in the 4.6 section with a pic of that part. I believe in maintaining my car cause it's cheaper than having to fix it.
  6. Headed back into town to get a new elbow. I will get 2 and put one in the trunk. probably gonna take an hour or so.
  7. Consider this could be a bad battery or loose battery cable.

    Remember no battery = no alternator.

    A prime symptom is the motor suddenly quitting for no apparent reason. Often restart is easy.

    If anyone is thinking this couldn't possibly be a bad battery because the motor was running at the time, you would be mislead. The battery is required to excite the alternator's field coil. A sudden increase in electrical load can over whelm the weak battery's ability to maintain the field coil. This leads to the alternator shutting down.

    Bottom line. Today's cars will not run right without a strong battery and charging system. Consider starting every electrical problem with a through review of the car's charging system. In the end, this will save you a ton of time.
    Jinx and mransr like this.
  8. OK back from the store. Replacement tube did not solve the issue. However with it installed, I can now keep the engine running by turning in the throttle position screw so that it idles at about 750. However, the engine is still having trouble. After holding the RPMs at any higher level and then releasing the accelerator it dips to below 500 RPM (or lower) then bounces up to 1100 and will eventually level off.

    The scanner is still not getting any codes from the ECU so it is making trouble shooting more difficult.

    Going to the place I bought my battery from tomorrow and will have them test both, battery and alternator.
  9. One possibility that comes to mind is that the IAC isn't working at all. It's generally a bad idea to attempt to adjust the idle using the idle stop screw. It may appear to work for a time but will fail when the temperature changes.

    What is the condition of the PVC system? Any leaks at all? When was the last time the PVC valve was replaced? Bottom line. Expect Idle problems if there's even a tiny vacuum leak.

    Here's some more information on how to trouble shoot idle/IAC issues.

    98gtDan and Jinx like this.
  10. i had that exact situation happen to me. turned out to be the fuel pump.
    Jinx likes this.
  11. Got back from the store, battery and alternator tested "good"
    Battery: 12.78v / 598 cca (rated 610)
    Charging system: no load = 13.89v / Loaded = 13.81v

    Things that influence running condition at full stop and idle:
    Depressing the brake pedal
    turning on the airconditioner
    increasing the RPMs then quickly removing foot from accelerator

    I did pull codes and did get the following:
    P1507 = Idle Air Control Underspeed Error (see P0506)

    what is P0506?
  12. PVC is in good shape, vacuum lines appear to be good from visual inspection. I don't hear any major hissing noises, but there still may be a leak (kind of hard to hear with the engine and fan running).

    Is my IAC the cleanable type? (this picture is not current, but it shows a better view without the cross brace)

  13. accidentally replied instead of editing.
  14. P0506 is a more generic OBD-code for idle speed too low.

    All of the things you mention -- brake loading, A/C clutch load -- and more (e.g. power steering cramp) are used by the PCM to use its idle air control valve to bump the idle a bit to maintain proper speed. I agree with wmburns: it sounds like the IAC isn't functioning. It may not be that the IAC is bad but it's the cheapest and easiest to replace.

    If it's not the IAC itself you might have wiring or PCM issues. Start with the IAC. Note that if you have fiddled with the throttle stop screw and replacing the the IAC fixes the problems you're going to have to re-set the minimum idle air (i.e. the throttle stop screw) setting.
    Jinx likes this.
  15. Yeah, I did not want to mess with the stop screw, but it was the only way to keep the car at idle, until I can get the issue resolved. I'm going to carry the hex key in the console to make adjustments daily, per weather temperature for now. The IAC valve is factory with about 100k on the clock and has possibly been cleaned once already. I really don't remember all the little maintenance things I've done in the past 10yrs with this car.

    So far I am narrowing it down with everyone's help. I don't think it to be a fuel pump issue because it does not surge at cruising speeds (even with cruise control engaged on a flat stretch of highway). However, when going down hill and the cruise control lets off, the engine rpms dip as if the PCM is trying to compensate for the sudden decrease in fuel.

    I have all the Ford part numbers and such, but holy hell they want 3 times the price and my first born son. $47 for 2 rubber elbows and a plastic tube (PCV crankcase tube) you have got to be kidding!
  16. No IAC is really serviceable no matter what anyone says. I have cleaned hundreds and it may allow them to work for a few more hours but that's it.

    Also its PCV not PVC! Crankcase Ventilation and not running pipe so the toilet flushes.

    No onto the "car wont run without the battery" BS. Yes it will. The exciter wire in almost any Ford is just looking at voltage from the fuse box. If the car is running and the alt is charging then you can remove the battery and it will still run because the alt has already made enough voltage to keep exciting itself. Basically its fapping. :) Now it is not recommended due to the ability of voltage spikes but it can work.

    For IAC, you can not use any type of pressure line. They do not expand but they cant keep from collapsing. You need a specific VAC line. Oreillys sells them in the helper section. Doorman makes them.

    Also the IAC is pretty much at 0% DC when running down the road because its only job is to move air AROUND the throttle body. If the throttle is open ...... you get the idea.

    Now that we have all that out of the way, this is what I would test if it was in my shop.
    1. Fuel pressure and fuel filter.
    2. Data log the TPS to make sure it is reading correctly and linear.
    3. Check the crank sensor. Both the plugs and sensor are known to be problematic.
    4. Intake leak test. Its a crappy intake and they crack and lose plenum gaskets very often.

    Try all that and then quote me so I remember to check back with this thread.
    Jinx likes this.
  17. Also, if its a Duralast IAC you need to get rid of it. I try to get Motorcraft only for Mustangs as most aftermarket ones are trash. They work well for other Fords but the design on the V8s leaves something to be desired. If you cant get a Motorcraft then get a BWD as they seem good about 95% of the time.
  18. Car is at the shop. I will let you all know what they find.

    On another note... I need instruction on resetting the throttle stop screw for when I get the car back. I recall seeing mention of backing it all the way off, then using a feeler gauge (between the screw and the throttle arm) re-tighten the screw until it comes into contact with the gauge. :shrug:
  19. You can get the PCV hose and valve really cheap from Rockauto.com and they are genuine Ford parts. The replacement plastic hose with the rubber boots and the PCV valve are like 50 bux. I just did this on my Mach 1 not too long ago. Only down side is you have to wait for them to ship it to you.

    You might want to add in a fuel pressure gauge to your car as it is good information to have while driving and it is great for troubleshooting too.

    Does your code reader have the ability to read the Ford TIDs or only the standard ODBII DTCs ?
    Jinx likes this.