Taurus Dies Mysteriously

Hello,

I'm new to the forum, but my car is being strange so I thought I'd ask here.

Problem: After braking hard to a full stop or when waiting at a light, my '03 Taurus will just die. It just turns off, and the dashboard looks exactly like it would if I turned the key just far enough to turn on the battery, but not far enough to turn it over. To rectify this, I put it in park, turn the key to the off position, and then restart the engine. Comes right back to life as if nothing happened, and doesn't cause me anymore problems until days or weeks or months later. This has happened to me about three or four times total over the past year or two.

I'd very much appreciate any help you guys can give me. I'm not too car savvy at all, but I enjoy learning about how things work (I'm an engineering student what can I say).

THANKS!

Oh, I forgot to mention: the car has about 130k miles on it.

Welcome to the forum! I'm a former engineering student, so I understand your desire to learn.

Does the engine stumble or idle low just before it stalls, or does it just stall with no real indications/warnings? Does it generally idle fine? Does this seem to only happen when the engine has been off for quite some time (cold)? When's the last time the car had a tune up (spark plugs, plug wires, fuel filter, etc)?

Assuming the engine normally idles fine, I'd start with the simple things, like making sure the battery cables are clean and tight. If you're on the original battery, you might consider replacing it in the event there are some loose cells inside. Have you happened to notice if when the car stalls, other electrical items stop working (radio, lights blink, etc.)?

If you're confident that the battery is not the issue, you might pull the intake air tube at the throttle body and check for carbon build-up on the throttle plate. You may need to open the throttle plate to see this well. If there is quite a bit of carbon at the throttle plate, you might be snuffing the air to the engine when the throttle snaps closed, especially if the Idle Air Control (IAC) passages are restricted or the IAC is a bit slow to respond.

-Rod

Thanks! The engine doesn't seem to stumble before it stalls, it just cuts off with no warning. It generally idles just fine, and I don't notice any relationship between stalling and how long the car was cold.

I'm pretty sure the car had a tune-up two years ago (replaced everything). I replaced the battery Fall 2009. I am hesitant to blame the battery because of (a) the ease with which it starts back up again and (b) all of the emergency lights come on briefly when this happens. Its just like when you turn on the battery without starting the engine. The radio only cuts off for a split second when the car stalls.

Is the air intake tube something that I could reasonably check myself(for example, with instructions from you or by googling it)?

The fact that the radio shuts off for a brief time along with it just stalling with no warning has me thinking you're experiencing a power issue. It might be interesting to check pending codes to see if there's one for a KAM failure or something. Any chance you have a portable oscilloscope that you could attach to the power input for the ECM and set to trigger on a falling edge of the voltage?

Checking the intake is pretty easy and likely something you could do. I don't believe your '03 would have the throttle by wire, so you should be able to, with the engine and key off, remove the black intake air tubing from the throttle body, manually open the throttle plate (or have someone press the accelerator to the floor). Look at the back of the throttle plate and in the upper intake with a good light and, if there is quite a bit of carbon in there, clean it out. I've been very pleased with STP brand Throttle Body Cleaner. It seems to cut through the crud and evaporate faster than most products I've tried. It would work for cleaning the IAC passages and valve as well.

-Rod

Something you may want to investigate is the ignition switch. I've had them get so worn the contact is not reliable.

I haven't gotten around to checking anything yet, but today it was really acting up. It started misbehaving while I was actually driving. It seemed to calm down when I pushed on the accelerator, or maybe it was just a brief thing. I'm not really sure.

I am definitely starting to believe that it is something electrical, however. The dashboard lights came on as in the past, and the radio cut out. Today, I happened to be listening to a CD when it happened, and, when the radio came back on, it started playing a different track than I was listening to when it malfunctioned. Also, the RPM gauge was jumpy. All of this happens in probably 30-45 seconds each time.

I may have to bite the bullet, and take it into a shop. I curious to see what you all think, though.

And, again, there is never any warning of trouble. It just suddenly malfunctions. Also, I took a look under the hood. I know practically nothing about what's under there, but I decided that I would check it out and make sure that there aren't any obvious problems (like corrosion on the battery, stripped wires, etc.). I didn't see anything.

The jumpy tachometer used to be a sign in a Ford of a faulty ignition control module. I doubt your 2003 has one of those, but that function is probably replaced in part by the Camshaft Position (CMP) Sensor. I'm not sure how you would go about testing this though if you don't have access to an oscilloscope and the problem is so sporadic.

-Rod

My roommate suggested that maybe there's a problem with my electronic fuel injection system. Is that related to my ignition control module or CMP? Im not 100% sure, but I think I've replaced my CMP before. I think I replaced it before I got my last tune up. The car was stumbling back then as if not all of the spark plugs were firing so I replaced the spark plugs, and had the wires etc. replaced.

My current problems seem different than last time. They could be related, but it's not misbehaving in the same way.

The CMP plays a significant role in both spark and fuel injector timing via the ECM.

-Rod

I remember the CMP being pretty cheap and relatively easy to replace. I'll try replacing it sometime this week.

So I've found the CMP in my car, but I can't quite get at it. There's a fairly large group of wires blocking my access. I took some pictures, and I will post them in a few hours.

I'm just wondering what they are, and whether or not they can be safely disconnected somewhere. There is almost no slack so it's proving impossible to just shove them out of the way. Seems to me, they are the main transmission lines for electrical power and communication between parts.

These are the pictures I took. The spark plug wire aren't a problem. I can move those pretty easily. Its the circled wires that I can't figure out how to move out of the way.

UPDATE: I took it to Midas because my roommates have had great service in the past from there. They gave it back today, and said they couldn't find anything wrong with my car. Weird. I'm debating taking my car to a dealership. Maybe Midas missed something that a dealership would be more knowledgable about?

Thoughts?

These very rare issues can get very expensive to troubleshhot, especially at dealer labor rates. Did you ever get the CMP replaced? I've never actually replaced one so I cannot tell you where it is in your photos.

-Rod

UPDATE: I took it to Midas because my roommates have had great service in the past from there. They gave it back today, and said they couldn't find anything wrong with my car. Weird. I'm debating taking my car to a dealership. Maybe Midas missed something that a dealership would be more knowledgable about?

Thoughts?
Check at the back of your engine on the left side for a square device that has 2 hoses coming out of it going to your EGR valve. This senses the EGR valve open / close state. See if it has a loose connection, or is corroded. Mine went bad and i couldn't even start the car, but, before it did, it did the same thing your car is doing, it would be intermittent started out when I had to brake hard for someone stopping short in front of me and could not be found until it went completely bad.
Unplugging it will allow the car to run, in most cases because it will usually place ground on the computer wiring causing shut down.

Something you may want to investigate is the ignition switch. I've had them get so worn the contact is not reliable.

I agree with that. It seems to be a bad ignition switch. Do you have a play when it's in ON position? I mean, if you play gently with the key while it's in ON, the dash lights disappear or you feel a play?

Like shorod said earlier, if the radio cuts off for 1 second after the sudden stall, it's a power electrical problem. Either the ignition switch or a bad contact in the under hood fuse box (but less probable).

Because of that, the CMP sensor has nothing to do with that. The bouncy RPM when engine is off is normal on these cars. I forget exactly why, but I remember that the rpm gauge is very sensitive. It can jumps from 0 to 1000 rpm quickly when engine is off.

The stumbling problem issue can be totally different from the stalling issue.
Taurus is know to have many different issues. Don't try to link them all.
This one can be related to weak fuel pump, bad EGR system, vacuum leak, bad PCV... or you repaired by changing the plugs.

I agree with that. It seems to be a bad ignition switch. Do you have a play when it's in ON position? I mean, if you play gently with the key while it's in ON, the dash lights disappear or you feel a play?

Careful not to confuse devices here. The ignition switch is different from the key cylinder switch. "Play" would be part of the key cylinder switch, which operates the ignition switch. If playing with the key causes momentary operation, that could still be the ignition switch causing the issue. You won't want to replace the key cylinder switch thinking that's going to fix the issue.

-Rod

You're right, the "play" test is no very relevant. Momentary operation could be normal.

So the ignition switch's contacts should be inspected.