2003 Gt Engine Failure

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

  1. When I thought my ECU was toast I sent it out to ecurepairnow.com. I spoke with them on the phone about it before hand and they were confident they could find the issue if there was one. It took a while to get it shipped there and back because I was cheap with the shipping and sent it ground both ways but they tested the hell out of my ECU and didn't find anything wrong. It was money well spent. Nothing was wrong with the ECU and I eventually found the source of my problems elsewhere. These guys are honest and good at what they do. Might want to ship the ECU out while you are waiting for Ford to come back with some new info. You need a 4.5 or 5.5mm socket to get the ECU out... can't remember which one exactly.
  2. so which do I have?
    • Ford ECM (95 and older) $150
    • Ford PCM gas OBDII (96 and newer) $175
    Service center still can not figure out what is wrong and are still waiting on input from Ford. They are suggesting that it may actually be the computer. I am seriously considering having a tech pull the unit today so I can ship it tomorrow.
  3. You have the OBD 2 one. Did you ever return the car to stock to see if the tune was corrupt? Or do a compression test or did the fuel filter and pump?
  4. Yeah, I returned it to stock tune. The mechanic has tested several items and everything is within factory spec. They have even put in help request to Ford engineering and they are slowly going through things. The electrical system checks out, fuel system checks out and the PCM is not throwing any codes.
  5. Outside of the idle does the car still move out or does it feel down on power?
  6. It drives normal with the exception of the high speed idle which I believe is causing the "cruise control" effect.
  7. I'd almost swap TB's with a friend and install a new throttle cable. Or take your Diablo and the idle down in your custom tune settings. Don't quit on this or swap a ton of parts unless you really want to. But my suggestions for part swapping start with fuel filter and going to the camshaft and crank sensors.
  8. Just spoke with the mechanic and after 3 weeks...

    Things they have checked:
    Mass air meter --- no change
    TP sensor --- no change
    IAC valve --- no change
    10 point test on PCM --- passed

    Things they have not checked, but are going to:
    Throttle cable condition
    Fuel filter
    camshaft sensor
    crank sensor
    Evap system

    I told them those were things suggested by others in similar situations. Why they can't check these things within a 3 week time frame I don't know.
  9. They ECU repair place only charges the full fee if they need to repair the ECU, the test fee is like 50 bux plus shipping 2 ways so about 75 by the time you get it back. They apply the diag cost to the 175 if they do need to repair. 75 dollars was worth it for me to have the piece of mind that the ECU was indeed healthy.
  10. Maybe @wmburns can chime in on them doing a load test on the alternator to see if the diodes are burned out.
  11. Is that a different test from what they do at one of the chain stores like Pep Boys or Auto Zone?? Because I had both the battery and the alternator tested before I took it to Ford. Both passed.
    #71 Jinx, Aug 1, 2013
    Last edited: Aug 1, 2013
  12. I think the parts store tests don't check for AC ripple, they just check if the battery is charging.
  13. If this were my car I would make sure there weren't any vacuum leaks. Then I would have graphed RPM's, TP-MODE, and IAC duty percent. While working the throttle, check that TP-MODE goes to "C/T" (closed throttle) each time.

    Next I would look at the relationship between RPM and IAC duty percent. Looking to see if the IAC duty percent is changing as this indicates that the PCM is attempting to adjust the idle.

    If the PCM is attempting to adjust the idle, are the RPM's changing in response?

    What are the ranges of the IAC duty percent? (Min/Max)?

    The ONLY method the PCM has to adjust idle is via the IAC duty percent. So one of the things we would want to know is:
    • Is the IAC duty percent between 40-60%. Values outside this range indicates a problem. Either too much or too little air.
    • Is the IAC duty percent changing and is the IAC valve itself actually changing in response? Cross check this by measuring the voltage across the IAC.
    • Is the PCM getting an accurate TPS closed throttle signal? Because if it's not, no further tests are possible as the TP-MODE has a major impact on how the PCM responds.
    • Is the PCM getting an accurate vehicle speed? Again the PCM does take the car's speed into consideration.
    The combination will give clues to where the problem really is. For example, let's say the PCM duty percent changes but the voltage at the IAC never changes. This would indicate a BAD PCM.

    Let's say that the IAC duty percent never changes. To me that says a the PCM tune is corrupted.

    Let's say that the IAC duty percent is ALWAYS below 20%. This says there no adjustment left in the IAC. Likely due to excessive air passing the TB.

    Has the throttle body been changed on this car? Perhaps from a different model year or after market?

    Did the Ford dealer perform a smoke test?

    A back yard method to test for Alternator AC ripple is to measure the AC voltage at the battery. Set the VOM to read AC. Do not use DC or auto. The value should be low (<0.2).
  14. ^ Printed all that out and will discuss with the mechanic.
  15. Called Service center today...

    Evap system has no leaks. Both camshft and crank sensor test OK. Fuel filter good. I am beginning to believe that it may very well be the PCM. He told me that they will not pull it for repair by 3rd party due to liability issues. If I pull it myself, do I have to disconnect the battery first?

    I am debating if I should do it at the Ford place, or drive it home.
  16. I would be surprised if they let you remove the ECU there and walk away with it. The car is inop at that point which deals wont want on their lot unless they know it is that way or that made it that way in the course of their work. Also they wont usually let people work on their own cars on dealer property.

    Yes, disconnect the battery first.
  17. I did get a chuckle out of this, because it's been sitting there for 27 days taking up space. ;) I'm going to just pick it up tomorrow and leave it in the gated area at my office (minus the PCM).

    Did a search... but all I was able to gather was:

    Disconnect battery :nice:

    1. remove sill trim by kick panel (with what?)
    2. remove kickpanel, one panel plug and a clip?
    3. remove PCM with socket set.
  18. Picked up the car today. Unrepaired and running like crap. Since they could not figure out what was wrong and had it for so long, they charged me zero dollars.

    I have since, pulled the PCM and boxed it for shipping to Illinois.

    Ford did check the main gaskets for leaks using the carb and choke cleaner method, and found no leaks. They also ran an EEC test on the PCM, with no problems found.
  19. Send the ECU out for testing. If it comes back clean it could very well be bad wiring or a bad ground.
  20. PCM testing is complete. Results are that there is absolutely nothing wrong with the computer.

    So now what do I do? I have my doubts that Ford did not do everything they claimed to have done. Reason being that the day I went to pick it up, they told me they were looking at stuff on it that morning, however I discovered a small 18 inch branch was laying across the hood that got blew out of the nearby tree from the storm 2 days prior. Which tells me that they did not have that hood up.

    I am not an electrician and don't have nor know how to use a volt meter, so testing a lot of the electrical stuff is out for me.