98 Gt Starts Fine Then Shuts Off While Driving/idling

Discussion in 'SN95 4.6L Mustang Tech' started by Bobby Rose Jr., Jul 27, 2013.


  1. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    Guys, new to forum but lifelong Mustang fan. I have 98 GT with about 140K on it, no real problems other than basic issues. Today while driving (car been sitting for about 3 weeks), car shut off after about 5 miles. Just lost power, shutoff with no warning. Able to restart with no problems, able to drive about another mile and same issues. Car shuts off after running for about 45-60 seconds everytime, regardless if in drive or idle. Check Engine and Battery light come on after car has cut off Have replaced IAC in past but issues are a bit different. Any help is greatly appreciated!!!
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  2. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    Also, last time I drove it, I had to jump start it and it ran fine. People I have spoke to said it could be the battery, but why would the car start fine everytime? Also, heard fuel issue, but why would it start and run fine for a bit, no stuttering just cuts off. Thanks in advance!!!
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  3. cobrabuck

    cobrabuck New Member

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    Have you had the code checked?
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  4. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    I don't have a code scanner, so I have not checked code yet. I will check tomorrow. Currentlt when I start there is no check engine light while running. Check Engine light and Battery light come on when car dies. Not sure this is a hard CEL though???
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  5. cobrabuck

    cobrabuck New Member

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    That I cant answer. I can tell you that buying a good code scanner is worth every penny and will pay for its self the first time you diagnose something and fix it yourself. The symptoms you are describing could be electrical or fuel related so it could be a lot of different things.
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  6. wmburns

    wmburns SN Certified Technician

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    +1 on having your own code scanner. They have gotten so cheap, there really isn't a reason for anyone that regularly works on their own cars to not have one. If you can afford an ODB2 code reader, by all means step up to one.

    Today's alternators are NOT the same as what was used in yesterday's cars. Today's high output alternators require the battery to excite the field coil. Therefore:

    no battery = no alternator.

    Weak battery or loose battery terminals = weak or intermittent alternator.

    A prime symptom of a bad battery is the car dies for no apparent reason at all. Just as strange, the car restarts easily.

    Bottom line......... Today's cars will not run right without a strong battery and charging system. Cut corners here at your own risk.

    Besides, wouldn't you feel really dumb to do a bunch of tests and change parts only to find out it was a bad battery all along? It's just too easy to check a battery and clean the battery terminals. Don't be "that guy" who ignores the corrosion cauliflowers growing on the battery terminals.

    Move onto to other possible causes once you know the battery and charging systems are in tip top shape.
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  7. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    I have heard about the batteries having to excite the alternator, which was new to me. I haven't bee able to get a scanner yet, but I may just purchase one, as suggested by you guys. The weird thing here is: the car starts fine and runs about 35 seconds EVERYTIME and then just cuts off with very little to no stumbling, and you can hold gas and it as no affect when it dies. Odd that it would do exact same thing everytime. I have checked battery cables and grounds with nothing conclusive found. I can hear fuel pump running when I turn ignition over.
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  8. cobrabuck

    cobrabuck New Member

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    I use the actron scanner and it works very well. There are different versions, simply get the best one you can afford. As to the battery. You can and should certainly check the battery but my problem as it relates to that alternator is that, if the alternator is not working because the battery is not activating it, you car would be drawing its charging requirement from the battery and would drain it.

    You would likely notice the lights diming etc.. If your battery was the only source of electrical power for the car it would not start after running for a short time. It could possibly be a bad cable.

    Start the car, hook a voltmeter to the both sides of the battery. If its charging 14 plus volts the alternator is working. if its less, it could be a weak alternator.
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  9. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    I swapped batteries with no luck. Lights or dashlights are not dimming at all. Anyone think this could be a CCRM related issue, as AC stopped working a few months back as well. Thanks for the replies, keep them coming as I appreciate the help immensely.
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  10. wmburns

    wmburns SN Certified Technician

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    Rather than saying that "the lights don't dim at all", it would be more helpful to post the battery voltage. It makes a difference if the battery voltage is 12.9 or 13.4 or 14.1.

    Since you are certain the charging system is in tip top shape, we can move on to more tests.

    The fact of the matter is there are many possible causes for the reported symptom. A short list includes:
    • bad/loose battery or battery cable
    • bad/loose battery ground
    • Bad alternator
    • Bad/loose main battery junction box terminal.
    • bad ignition switch
    • bad CCRM
    • For applications with a 2 speed fuel pump return system, bad HI/LOW speed fuel pump relay or ballast resister.
    • bad PCM
    • about a 100 possible motor causes including ignition, fuel, vacuum leaks, MAF, and so on.
    Trouble shooting a problem like this is a process. In my experience it's best to start based upon the symptom and the easiest/most common causes first. I tend to try tests instead of "parts changing". Especially the tests that are fairly easy to preform.

    An easy way to confirm stable voltage is by using an "add a fuse". Use the add-a-fuse on the I/P #18. Attach a volt-ohm meter (VOM) and use this to monitor the voltage while driving. What this test should do is to rule in/out what the voltage is doing at the time of the problem.

    I/P #18, this is the pilot duty circuit from the ignition switch. The output of I/P #18 goes to the CCRM. So knowing what is happening at this point may tell us which way to look next (down stream towards the CCRM or to the ignition switch).

    An ODB2 scanner and a set of wiring diagrams may make short work of this problem. The ODB2 scanner could be used to monitor MAF values to see if there is a sudden drop BEFORE the motor dies. There are tons of other tests that it's possible to do with an ODB2 scanner.
    Last edited: Aug 3, 2013
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  11. cobrabuck

    cobrabuck New Member

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    As WMburns said there could be many issues or problems but start with the easiest like the battery cables or ground.

    You mentioned the air stopped, stopped how? not blower motor or just not cold? If it does not turn on at all and you have checked the simple stuff that might be worth investigating. Not that an AC unit will shut off the car but you may have an electrical issue that is somehow causing both issues. My second guess would be the MAF or Some sort of fuel delivery problem. but do the tests.
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  12. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    I had limited time today to check with Snap-On scanner with all the bells and whistles. It "had" 2 stored codes, one for IAT temp high and one for PATS theft key detected or something along those lines. I some how deleted those, as they no longer stored. Dumb me! I do believe those may have been old codes, as I had issue with chip in my key a while back. I believe the IAT temp (Intake AIR temp) high may have been while I was troubleshooting MAF or air thermistor early this week. Now I am showing no codes and scan is coming up incomplete with engine running or just with key in ON position. Obviously car will not stay running long enough for run scan to complete, but it is also coming up incomplete during key ON test. Anyone on thoughts of incomplete test? When doing key ON engine OFF test, it starts by turning on cooling FAN, I can hear click in CCRM and then cooling fan comes on. Cooling fan runs for about 10 seconds, then I hear another click in CCRM and scan then stops and says incomplete. Also when car shuts off I hear a click in the CCRM that immediately cuts car off. So it looks as if the "something" is telling the CCRM to turn off fuel pump relay???
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  13. wmburns

    wmburns SN Certified Technician

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    IMO you may be looking for problems in areas that are unlikely to help you. Why? Your own report stated that the motor shuts off suddenly. IF this were a fuel pump problem, the motor would loose power and stumble before quitting.

    Consider the fuel pump is supposed to run for a few seconds at initial key on and then SHUT off until the motor starts. So hearing the fuel pump run and then cut off would be normal depending upon the sequence of events. However, one would expect the fuel pump to restart after the motor "hits". If this is not the case, then it bears looking into.

    Also note that the 98 uses a two speed fuel pump. The low speed uses a ballast resister and a relay to reduce the voltage to the pump and slow it it.

    Remember that the CCRM controls power to the PCM, Fuel pump, AC, and cooling fan. So the click heard when the motor quits could be any of the relays. Knowing which relay is clicking and knowing if the relay dropping out is causing the motor to quit or the relay is dropping out because the motor quits maybe a very important clue.

    I got the impression that the car will drive sometimes for miles before quitting. That was why I made the suggestion to monitor voltage while driving. I still believe it would provide clues to "know" if the voltage is stable when the problem occurs.

    If you don't have an "add-a-fuse", then monitor the voltage to ground on the fuel injector Red wire. Look to see if the voltage drops before the motor quits.
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  14. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    Thanks for response! The car will run between 35-45 seconds and shutoff every time, no matter what. I focused on the CCRM simply because I never noticed the "clicking" before now. I can noticeably hear a click in CCRM before car shuts off, I have noticed it does stumble a very slight bit. With the snap on scan tool I have, I can monitor just about everything the car is doing while this is happening. Also, if the fuel pump never starts when motor is running, I would believe that the fuel wouldn't last for 45 seconds while driving, as it does when idling. I do remember battery voltage sitting was 11.6V and around 13.5V with car running.
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  15. Kilgore Trout

    Kilgore Trout Fried or Broiled ?

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    Wmburns is a skilled tech I am sure he will figure it out. Just curious have you inspected the plugs? With those miles you should look at them...
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  16. wmburns

    wmburns SN Certified Technician

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    To rule in/out a fuel pressure problem, measure the fuel pressure. Then you will KNOW.

    A low tech suggestion is to have a buddy LISTEN for the fuel pump to run. Call out when it runs and when it quits.

    I personally would measure the fuel pump voltage at the trunk IFS switch (DG/Y). This would tell me if the CCRM click is related to the fuel pump.

    I would also look at the PCM operation mode. For example, if the motor dies right when the PCM switches from "open loop", to "closed loop", that is an important clue.

    There should be a PID for the speed of the fuel pump. Values like low speed or high speed. If for example, the car dies when the PCM changes the fuel pump speed. That's an important clue.

    Monitor the MAF values. If the MAF changes right before the motor dies, that's an important clue.
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  17. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    Thanks for the responses guys :) All the info you have suggested I check, I believe is displayed on the scanner I using. I havent had much time to work on the car this week, as I work 630p-630a ughhhhh. I will look into all the values you have stated above and let you know how it goes? I have noticed that there is a bunch of "dirt/gravel" in at the CCRM connector, could this be causing a short to ground, causing my symptoms? Anyhow, I am going to clean/blow that out.
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  18. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    Ok guys, after being on vacation I have found a little time to troubleshoot. I have performed most above test with no smoking gun. Car never gets to closed loop before shutting off. MAF values are unchanged. I do not see a pump speed PID however after monitor several parameters and restarting car several times, I now have code 0231 secondary fuel pump circuit low. Also noticed Fuel Tank pressure is showing 5.12 volts and will not change, not sure if this is related or not. Manual states it should be in 2.5v range with gas cap off.
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  19. wmburns

    wmburns SN Certified Technician

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    The P0231 DTC is your smoking gun. This is confirmation that the hi/low speed fuel pump relay function is NOT working. Almost certainly, the motor dies when the PCM attempts to switch to low speed mode. The diagnosis can be confirmed by testing the fuel pump voltage at the IFS switch. If the voltage goes to zero, this confirms the diagnosis.

    There is a set of pin point tests X180 in the Ford service manual on how to trouble shoot. The decision tree is very different between "engine starts" and "no start".

    For the "engine start" decision tree:
    • Open FP PWR circuit between the low speed fuel pump and FPM splice
    • Damaged PCM
    The fuel tank pressure PID is not your problem. A bad FTP sensor would only affect EVAP purge.

    Trouble shooting the fuel pump hi/lo relay and ballast resister would be much easier with a Ford service manual and wiring diagrams. If interested in getting a copy for yourself I maybe able to help. PM if interested.

    Cheer up. You are actually closer than you might think to fixing this yourself.
    Last edited: Aug 27, 2013
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  20. Bobby Rose Jr.

    Bobby Rose Jr. New Member

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    Thanks WMBURNS, I will send you PM. Thanks!
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