5.4 almost stalling issue.

Discussion in 'Ford Truck Forum' started by mxer201, Apr 1, 2016.

  1. mxer201

    mxer201 Full Member

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    My 01 Navigator with 183k miles has an issue with "almost" stalling. After heavy braking then immediately pressing the accelerator, the tach will sometimes drop to 200 or 300 then back up above 1k and runs fine. For example, traveling at 55 to 60 mph, start braking to make a 90 degree right turn. Let off the brakes and press the accelerator while turning and the near stall occurs. I can almost predict when it will happen. Already replaced the IAC and getting ready to replace the vacuum rubber connectors. I'm thinking vacuum leak. Suggestions or ideas? And I'm sure this has been thoroughly discussed, didn't have time to find the other post.
     
  2. jkeaton

    jkeaton Full Member

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    What engine? Last tune up? Just start or has always done it?
     
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  3. mxer201

    mxer201 Full Member

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    5.4
    Tune up in 2015
    Not sure when the problem started.
    New fuel pump a few months ago.
     
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  4. eze

    eze Full Member

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    Start with basics fuel pressure ,vacuum leaks ,fuel filter,air filter ,ect could be possible tps sensor ,could be possible bad vacuum booster ,you can check for vacuum leaksby spraying carb/choke cleaner around where the intake mounts to head on vacuum hoses ect if there is a leak idle will change when the spray enters the engine .does it happen if you coast down to a lower speed with out stepping on the brake then throttle up?
     
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  5. mxer201

    mxer201 Full Member

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    I'll try the coasting like you suggested next time I drive. Once after it did the near stall, I accelerated, pressed hard on the brakes, then throttled up, trying to make it happen again. Can be scary sometimes, especially when pulling out on to a busy highway. One time pulled up to a stop sign, looked, no traffic, off the brakes, on the throttle and felt like it nearly fell flat on it's face but then took off. Enough to make my heart jump.
     
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  6. eze

    eze Full Member

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    Yea I can understand you feelings can be very scary .I'm thinking that if it only happens after stepping on the brakes hard that you are losing vacuum causing the delay the brakes receive there power from the brakebooster and it works off vacum it has a rubber diaphragm that can dry out over time and have small tares that will only leak when that area of rubber moves it doesn't happen often but if changed a couple hundred in my life also before going and changing it I would test for any possible vacuum leak around intake manifold , plenum, hoses ,lines ,even at or around vacuum solenoid's its very common for fords to have cracked hard plastic vacuum lines be sure to spray them well all over
     
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  7. mxer201

    mxer201 Full Member

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    Well, been driving the gator today. Whenever pulling away from a stop or near stop, I have been very gently rolling on the throttle. Working so far, tach needle not dipping down into the 200 or 300 area. As long as I'm not having to pull out in heavy traffic. I agree with the idea of a vacuum leak and will experiment with spraying cleaner fluid or equivalent in suspect areas. I did forget to mention it has set code P0442. Cleared the code and waiting for it to happen again unless I find something doing the spray test.
     
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  8. eze

    eze Full Member

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    That code is for a evap leak depending on where the leak is it can be a vacuum leak causing your problem if the light comes back on start by changing the gas cap and 're set if it. Comes on again your going to need to track all evap lines to the tank it could be a clog or faulty evap solenoid or dried and cracked.rubber line or broken hard plastic line but if the leak is under the hood it can cause your other problem
     
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  9. leolkfrm

    leolkfrm Full Member

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    i would spray the wires with water and see if it misses....bad wire would create a slow speed stubble
     
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  10. mxer201

    mxer201 Full Member

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    Update, sprayed the vacuum connections. No change in the idle. CEL came on again for code P0442. Decided to take it to the dealer thinking the problem might be something deep. Big mistake. Said the problem was the new fuel pump that I had installed a few months ago. Wanted $1800 to replace it. Uh, no. Still got stuck for a $133 diagnose fee.:mad: Took the vehicle to the mechanic who did the fuel pump. He did a pressure smoke test and discovered a rubber tube on top of the tank was leaking. I asked if he would drive the vehicle a couple of days to see if the near stall would occur for him. Will update again later. Forgot to mention I did replace the gas cap with a new Motorcraft cap when the IAC was replaced.
     
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