Car just stalls for no reason....
 

Hi Everyone...got a problem here that my mechanic just can't seem to figure out. The car just stalls during normal driving on a flat road. My immediate suspicion was a fuel pump or fuel filter issue.

The first time it happened, i was just driving the car, made a left turn and suddenly it just shut off. A/C was still running, electrical components still running but gas was slightly less than 1/4 tank. When i try and crank the car, it cranks fine and almost sounds like its gonna turn over, but to no avail. I'll even try stepping on the gas slightly during crank or just when it sounds like its gonna turn over, but nothing. Tow truck guy arrives, takes it to the dealer 8 miles away and when i get to the dealer, the guy starts it up like nothing happened. So, i figured maybe the gas gauge got stuck and fill it up with gas and it runs fine.

2 months later, the same scenario except that it doesn't die while driving. This time my gas was about 1/3 remaining. It simply won't start back up after about 20 minutes of driving. So, thinking that maybe its a fuel pump problem or something similar i just jump up and down on the rear bumper to give the car a good shake. 10 minutes later while on the phone with AAA i crank it up and it starts. Not sure if the jumping on the bumper deal was the cause of it working, but it started. So i immediately drove it to my mechanic and after a day of working on it, they can't figure it out.

They said that it might be my MAF sensor because my K&N air filter is dirty. But then i stated that if it was my MAF, then wouldn't this be a continuous problem and not an intermittent one? They checked the computer and didn't find any codes, so i'm confused as to what it might be. Don't want this to happen again because my wife and 1-year old daughter drive in this car every day 30 miles each way. Luckily it happened both times to me. Maybe i'm just bad luck.

Can anyone help?

Oh yeah, forgot to note that its a 2000 Expedition EB 2x4 5.4L.

Wow, this could be a tough one. I had a '98 Mountaineer that intermittantly died. I had it at the dealership half a dozen times for the problem, but they could never get it to die when there so never did anything to fix it....naturally I was POed. Back in the old days, when Fords died it was the electronic control module; a five minute replacement would get you going again. Now days there are so many electronic components, it's hard to pinpoint.

Good luck in diagnosing.

Thanks Jim. I just got off the phone with the mechanic just now and they still havent been able to diagnose. It sat in their garage for a few hours on idle and still nothing so they said that they would rather not guess at it since a replacement fuel pump is about 700 bucks to do. They also said it could be the IAC valve (Idle air Control for those newbies like myself) but they aren't sure. Whatever it is, they couldn't duplicate so now i'm stuck guessing at the problem. I might just bite the bullet, do the Fuel pump repair and gamble on the problem. They did tell me that if it is the IAC and they only replace the fuel pump, then they would do the IAC repair for free if i bring it back. The car just acts like it runs out of fuel. Are fuel pumps known to go bad this early? The car only has 60k miles on it. The only things in common between the 2 incidents is that i was running the A/C, and it was a warm day in socal (80F), and there was less than 1/3 tank of fuel remaining. If you (or anyone else reading this) were to gamble on the problem what would you guess it to be?

IAC from autozone costs only $42, all you need is a 5/16 or 8 mm racheting wrench (there is no room for socket wrench specially for the lower bolt) and a bit of patience to replace this part which is near the firewall on top of the engine, with one electrical connection (could use dielectric grease too for that). You could even clean it with wd-40 and re-install, and by removing it, you will see right away if the valve is dirty with deposits or if it is stuck.

I would definitely start there, considering the cost of fuel-pump replacement.

I suppose it could be the IAC valve, but when mine went out my Expy would start then immediately die, start then immediately die, etc. Sometimes I could keep it going if I "feathered" the gas pedal. Mine never died while driving.

I can't imagine it being the fuel pump. I certainly wouldn't start with $700 repair before doing a $50 repair or two.

The thing that confuses me the most is that the 2 times it stalled i was somewhat low on fuel, the car wouldn't turn over immediately after dying until about 20 minutes later once things "cooled" down a little and the car had been running for over 30 minutes. I've had a car run out of fuel on me before and this feeling was just like that, which is why i'm thinking its the fuel pump. What are the common symptoms of a failing IAC? Is it normal for a bad IAC to run 2 months in between failures?

My experience with IAC failure is as buzzard described, would start, would not idle. When I removed it, it was stuck (can't remember if it was stucked open or close).

Anyway, I realized now that you have it in the shop, wondering how well you know your mech, since as I stated, it's really not a big deal to remove it just to see and check the condition of the valve. This is discounting any possibility that there is electrical issue on the IAC and not just mechanical.

IAC is a common problem on these trucks. Its a cheap fix and good investment in preventive maintenance.

But is it common for the IAC valve to not start, then suddenly work for 2-3 months straight, then suddenly stop again, etc.? Or is it once it starts giving problems, its constantly giving problems.

When mine went, it caused random problems (worked fine one day, then not the next, then fine again, etc.). This was many many years ago and I didn't even know what the IAC was. Of course I came on here and with a little research quickly learned exactly what the problem was. I tried cleaning mine at first but it gave out again shortly thereafter, so I went to the dealership and got a new one for around $70 (back then they weren't even available at auto parts stores).

If you know that yours has never been replaced, it might be a good idea to replace it as davisenvy mentions. If you have 15-20 minutes and can find the dang thing behind the throttle body, it's an easy R&R.

The best/easiest way to figure this out would be the following:

1. Put fuel pressure gauge in trunk.
2. Drive until it stalls
3. Immediately hook up FP gauge
4. If when switching key to run/start and attempting to start you do not have 30+ psi = you have a fuel delivery issue.
5. If you have good FP, and the car is good (starts right up) after "cooling off", I suspect you have a bad CKP sensor (crank position). I worked on a mod-motored car lateley that had this exact same problem to the T. It was an intermittently bad CKP sensor.

Good luck!

If it is the IAC, the next time it stalls, hold the pedal down about 1/2 way and crank it. It should start right up. If not, then it is not the IAC. It could be a crank or cam sensor going bad. Not real common, but does happen.

I realize this is an old thread but thought i would update on this issue. Even the mechanics couldn't figure out what was causing the problem and they said it would be pretty expensive to eliminate it via trial and error. So based on the symptoms i was getting and taking an educated guess, I went ahead and asked the mechanic to just replace the fuel pump (back when i had started this thread) and i'm happy to say that over 3 years later the issue has not reoccurred. Looks like that was the culprit.