Engine shuts off while driving without warning?

Hello,

I have checked for any recalls or Technical Service Bulletins for anything regarding this problem and didn't find anything. A problem like this could be caused by a wide variety of things, so all I can really do here is attempt to point you in the right direction and go from there. So this could be an intermittent problem with the Crankshaft Position Sensor(CKP) or the electrical connector or loose wires from the CKP to the Power-train Control Module(PCM) or "computer". In the diagrams down below I have included a description of the CKP sensor, a wiring diagram of the CKP circuit, the location of the ground wire for the RF shielding, and a guide for tracking down poor electrical connectors and intermittent problems in an automotive electrical circuit for you to go through. Please go through these guides and check the CKP circuit for an intermittent problem and get back to us with what you are able to find out. We can go from there.

Thanks,
Alex
2CarPros

Thanks Alex so much! I will review the information you sent and let you know what I learn.
Tom

Alex, I started looking at the schematic images you posted (I have electrical experience), I went to zoom on them so I could read the writing but the resolution is kind of bad. Any chance the wiring images could be of higher resolution?

Thanks- Tom

Alex is absolutely correct, if I could add something from a clue that you gave us about the fuel cap light. On a rare occasion I have had the fuel tank pressure sensor short to vref which will cause the power-train control module to shut down. The vref circuit is a 5 volt circuit that several sensors use as a reference to for proper sensor voltage feedback. The fuel tank pressure sensor tells the power-train control module how much pressure is in the fuel tank, when the PCM tells the purge valve to open and pull a vacuum on the tank, the voltage will go from 2.65 to 1.50 approximately. And when the sensor fails, it usually fails high at 5 volts so now the PCM thinks that the fuel cap is off because the voltage is not coming down when a vacuum is commanded. Throttle position sensor, dpfe/egr sensor, fuel tank pressure sensor, are some of the most common vref short failures that I have seen. This is only one scenario, but if the vehicle will not start, probe the brown with white wire for 5 volts with the key on at any of those sensor connectors, or just unhook them in a no start condition to see if it starts. And if you have a scan tool that can look at the sensor readings, the ftp should read 2.65v with the key on engine off.

Okay, I located the CKP. The harmonic balancer was repaired a few years ago if that matters. The sensor is very greasy since there is a slow oil seepage from one of the bearings on the engine front. I could not easily get to the wires of the sensor, it is harder to access than expected (no lift, ramps, etc). Would the failure that caused the engine to stop show in the error codes? I think I can read them or I would get a parts store to do that.

Hello again,

This type of failure should throw a Direct rouble Code(DTC), but not always. If you have a code reader it should be fairly straight forward on pulling the codes. Here is a link explaining how to do that:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If you don't have access to a code reader than you can go to your local auto parts store, like AutoZone and they will read them for free. Please get back to us with what the codes are and we can go from there.

Thanks,
Alex
2CarPros

Great, I should be able to get to a parts store in the next few days and I will ask them to do a code read. The engine light has not come on, would that indicate a DTC was not thrown?

Hello again,

The Malfunction Indicator Lamp(MIL) or "check engine" lamp is illuminated when a Direct Trouble Code(DTC) is set. It will be flashing when a catalyst damaging DTC is set. When you turn the ignition key to "RUN" the MIL should light up, and if there are no DTC(s) set, turn off. This is known as a bulb check to make sure the bulb is working. So if the MIL is not illuminated then there is no DTC set.

Thanks,
Alex
2CarPros

Thanks Alex, I guess I`m back to square one. I`m going to examine again getting at the CKP but it seems in a tight spot, it will be hard to determine an intermittent electrical connection with little room to work. If I knew the CKP was the problem I`d really go after it.

Alex, I spoke with a family member that has extensive experience with Ford Mustangs. He stated he had a similar issue to mine with the engine suddenly shutting off without warning. What fixed his was replacing the alternator. To me this seems an unlikely cause for my Explorer failures by I wanted to run it by you. I did just replace the alternator about 9 months ago.

Bad alternator diodes can induce noise in the system and corrupt the crank sensor signal. Have replaced tons of alternators for this at my dealership,most of the time with no codes present or a code in continuous memory with no light on.

Thanks BMDOUBLE... I replaced the alternator last fall, got a cheap one from China through ebay. Is the source of significant concern? Does it really make much difference?

Hello,

Actually, yes it does. hat old adage you get what you pay for. It is as true today is it has ever been. I would stick to Motorcraft (Ford), Delco, Denso, Bosch, or manufacturers of this caliber for replacement parts. There is a reason that vehicle manufacturers sub contract to companies like these for parts such as OEM fuel injectors, O2 sensors, and others. BM Double is very knowledgeable when it comes to the Ford Brand so you might want to check into this and get back to us with what you find out, please.

Thanks,
Alex
2CarPros

Yes sir, Motorcraft seems to be the best choice for alternators and not just because I'm a Ford guy, but because I've had to remove literally hundreds of customers' aftermarket alternators (brand new) because they did not work correctly.

Okay, is a re-manufactured Motorcraft okay, or does it need to be new? The new is quite expensive.

re-manufactured is good.

Today, 9/22/2019 I had a Motorcraft re-manufactured alternator installed in my vehicle listed above. I will update here if/when the sudden engine stop happens again, or maybe to give an update on how it is going. Thanks everyone for your helpful suggestions, you are very appreciated!
Tom

Awesome! Youa re welcome!

Hi Everyone...

It is (12/15/2019) almost 3 months since installing the Motorcraft alternator, so far no engine sudden stop.

Excellent!

Hi All!
I`m sad to report a few weeks ago my Ford just suddenly stopped running again (early June, 2020) while driving easily (then it restarted normally), this happening several months after replacing the alternator with a rebuilt Motorcraft unit. The car was not being driven much otherwise I suspect the stop would have happened sooner. My guess is a bad connection somewhere in the electrical system. I plan on keeping the car till next year and for now will drive it locally and be aware of the issue, and it will be replaced in 2021.

Thanks for all the comments!
Tom

We just had this problem on the site with a similar car the person ended up replacing the MAF sensor which fixed the problem. The sensor can short intermittently causing the problem which makes sense it was okay for a while once the alternator was replaced. Here is the sensor location. Check out the diagrams (below). Please let us know what happens.

Hi Ken.

Thanks for the suggestion to replace the MAF. It looks like an easy part replacement so I have ordered an exact replacement part that should arrive in a few days. The issue with the car has been frustrating and if the part fixes the problem it will take a while to know and some apprehensive driving wondering if the car is going to suddenly stop. I will definitely update with what happens.
Thanks again,
Tom

Okay..
I`ve replaced the MAF sensor and I will report back on how the car does regarding sudden stopping.

One question, I noticed that someone left the air intake box top section out of place, and one of the clamps is missing a piece. I placed the air intake box top section back into place over the bottom (holds the air filter) and I`m using the one clamp. Could having the air intake being (partially) unfiltered caused an issue with the MAF sensor? I will look to replace/repair the bad clamp.

Tom

That will cause the sensor to go bad yes because of too many contaminates. Can you please shoot a quick video with your phone so we can see what's going on? that would be great. You can upload it here with your response.

Okay, here is a video of my car and air box. I guess I should always look the car over after a repair. It starts fine and all seems Okay, should I get the air box clamp before driving it any? It still closes fairly well with just the one clamp. Seems I will need to find this part online or in a salvage yard.

Go to your local salvage yard, preferably a pick-n-pull because it's cheaper, and get you an air-box. I've actually had several explorers with a stalls at idle concern be cause by a loose air-box because the air from the fan will blow into the box and passed the sensor causing an incorrect voltage reading and thus overestimation of what is actually going on. But I don't think that is what is causing your original concern, and don't buy another MAF sensor, my opinion but it should be fine. I would retest the charging system on the vehicle with a good charging system tester like a vat-45 or equivalent, so you can get a reading for the diode test pass/fail. Also a very thorough wiggle test of the wire harness near the power-train control module and also around the battery cables, have had issues there as well. Just a few picks from my mental Rolodex for ya, hope it helps!

9/16/2020 - It has been a good while since I replaced the MAF in my 2005 Ford Explorer, and as it turned out it has been driven much more than expected this summer. But I am very pleased to report that the vehicle has not shut itself off once during this time. I did secure the air box together with wire ties until I can find one for the missing clip. I may never know for 100% the MAF was causing the engine-shut-off problem but it sure seems that way now.

Thanks for all the helpful input!
Tom

This vehicle runs well and has plenty of power, but occasionally the engine will just die. It can happen at 10 mph or 60 mph. It will crank back up and run. Appears to be an intermittent problem. Pulled two codes from the computer:
P1633 KAM (Keep Alive Memory) Voltage Too Low
P0462 Fuel Level Sensor Low Input

I don't know that these codes have anything to do with the problem we're having with the vehicle. I've checked some of the simple stuff like making sure there is plenty of fuel in the tank, and I checked the battery voltage (a good 12.6 volts).

What do you think?

It sounds like a classic crankshaft angle sensor problem. When these sensors go out the may or may not trigger a code.

Here is a guide to show you what you are in for when doing the job:

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Here are the symptoms:

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Below is what it will be like on your car.

Please let us know what happens.

Cheers, Ken

Ken, thank you for your answer. It was informative and incredibly detailed. Your answer jogged my memory of a 1997 Ford Explorer I owned. It would put me down occasionally, and I found quite by accident that by twisting the wiring going to the crank position sensor, I could start the car and get it going again. Based on your answer and on my past experience (this vehicle didn't struggle to run nor did it run poorly before stalling; it just stopped dead in it's tracks), I took a chance and replaced the crank position sensor (just under $20 at O'Reilly Auto Parts). I am still test driving it and haven't had a problem yet. Time will tell.
Underneath all the fancy electronics, engines still need a spark, adequate fuel delivery, decent compression, and correct timing to run. A spark tester confirmed that the ignition was at least firing. No Schrader valve on the fuel rail, so I skipped this test, and I decided that the compression and engine timing were fine (the car runs so well). I'm basically taking a shot in the dark since I don't have complete diagnostics to back up my repair actions. I also cleaned up some of the grounds including the body to frame ground straps.

Detecting a crankshaft angle sensor failure most of the time you will need an oscilloscope which can read the wave form.

Please let us know what happens.

Cheers, Ken

Recently my Explorer stalled on the highway while we were driving. It seemed as if the security light lit up and then the dash board lit up followed by the engine cutting off. We had to coast to a stop and then started the truck up again right away. The following day, the same thing happened but this time the Explorer would not start again. We had it towed to our Ford dealership where they hooked it up to a computer but it showed their were no issues. We then took it to another mechanic and they could not diagnose using the computer either. There is something wrong but the dealership nor another mechanic could not diagnose. Do you have any ideas on what this problem could be? Is this a common issue you may have heard of?

Hi thanx for the the donation, you have the classic symptoms of a bad crank position sensor, not only that , but these usually dont show up on a computer scan, nor does it show a check engine light. have it checked out, most likely this is the problem, Also if you can mimic the problem again, of course, in your yard or somewhere off of the street. it would good if you could check for fuel and spark. that is the first thing a mechanic is supposed to check in this situation. but just from what your telling me, I suspect the crank position sensor

https://www.2carpros.com/how_to/how_to_test_an_ignition_system.htm

https://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

I wanted to add that we can drive the car from anywhere between 1/2 - 1 hour before the car stalls. Its happened about 3 times now. Do you still believe its the crankshaft or could it be something else?

yes I do suspect the crank sensor, although it could be the fuel pump relay. something electrical is getting hot and then causing an open circuit. that is usually the crank sensor, but it can be a relay too. this is why we need to test fuel pressure and ignition spark to know which direction to go. but I still would check the crank sensor, unless you can do the testing first.

My explorer v-8 will start but does not stay running. There is no Schrader valve anywhere to test pressure. Not sure what to do

If there is no port on the engine, you need to test pressure at the fuel filter.