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This is a Ford Explorer Sport 2001 4L V6 with about 90k miles.

I've started to get this problem as of late. Once in a while, the engine simply refuses to start after the car has been run for some time. The engine cranks but shudders and dies right away. Keeping my foot on the gas doesn't help. After a few minutes of trying, it does start, but I'm just afraid that one day it will get me stuck in a predicament.

Other technical details: sometimes it happens in the mornings too, but only in the winter. Sometimes (very rarely) the engine dies when at very low rpm. This is usually in the morning too, like I would start it and after 2 seconds of running the engine just chokes. And in extremely rare cases (I think it happened once about a year ago), it died at a stop light. It restarts just fine right after though. It also has a rough idle sometimes, it could get to 1000 rpm after it starts, suddenly drop to 500, then go up and drop again. This only happens for a few initial seconds and only after a cold start.

Any help appreciated, thanks.

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  • Welcome to the site. This could be simply needing a tuneup, but you haven't mentioned anything about the condition of the engine/car. When was the last time this was tuned up (plugs, wires, air filter, fuel filter, etc)? Is the check engine light (CEL) on? Have you had the codes read?
    – CharlieRB
    Commented Jan 23, 2017 at 18:00
  • Thanks for responding. I really don't know when it was checked last by a mech, I bought the car at 80k and haven't had it checked at any point. I don't have any codes. The condition of the engine Im not too sure about.
    – VanillaSnake21
    Commented Jan 23, 2017 at 19:25
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    Assume then that it hasn't been done. In that case, a tune-up can resolve a lot of issues like you have described. Pull a few plugs and check the condition. Same for the air filter. If they look bad, then it is time for a complete tune-up.
    – CharlieRB
    Commented Jan 23, 2017 at 20:13

2 Answers 2

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My best guess would be the crank angle sensor, the cars ECU (computer) relies on the crank angle sensor to fire the injectors and spark plugs, if the crank angle sensor is not working correctly you will get all kinds of problems including what you have mentioned.

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  • It's very unlikely that he would see seasonal variation if this were the case. Similarly, the problem shouldn't be dependent on temperature if it were a crank angle sensor.
    – Hari
    Commented Feb 23, 2017 at 2:39
  • One of my previous cars behaved differently under different conditions, perfect when it was cold, misfired when it was hot, at one point it just stopped running, under advise from an auto electrician friend I poured water over the crank angle sensor and the car ran again, had the CAS replaced and the problems disappeared for good, I agree it's rare that a CAS will behave like that but it does happen.
    – Martin
    Commented Feb 24, 2017 at 3:59
  • Well, that's evidence enough it could be worth checking. As usual though, start with the obvious causes, then progress to the less obvious ones.
    – Hari
    Commented Feb 24, 2017 at 4:58
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I face something similar with one of my cars. I've noticed that, when cold, it takes a moment to start up properly and when warm it surges. In my car, I know the issue is linked to the ICV or Idle Control Valve.

It's possible that your Idle Control Valve is gunked up, so it doesn't work properly.

This would explain many of the idling issues you are facing, but not the inability to start the car while holding the gas pedal. That said, ICVs are easily fouled by oil from the crankcase ventilation, if it doesn't go straight into the manifold. Cleaning the ICV may help.

It is also possible that you have a vacuum leak.

Vacuum leaks are the ground loops of the automotive world. They're often overlooked, cause mysterious (and sometimes seemingly unrelated) issues, and can be troublesome to track down.

Do you have issues with braking at all? The brake booster runs off engine vacuum, so a vacuum leak can also affect the amount of force you need to exert on the brakes to stop.

Sometimes vacuum lines get pulled by accident when performing other work. If that's the case, it's easy enough to find out where it goes and reconnect it. Replacing lines isn't too bad either.

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