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Hello, I'm new here and having a problem with my 99 F150 that is driving me nuts. The truck is a 4X4 supercab, with the 4.6 motor, 141,000 mi. During cold weather it runs great, but as soon as the temp gets into the upper 70's or higher I have a recurring problem. The truck starts right up and runs well, but when it is shut off it will not restart until it has sat for over an hour. It has also stalled at speed on the feeway when the outside temp was in the upper 90's to low 100's. So far it has always restarted after sitting for awhile. I took it to the dealer and they kept it for 3 days, but could not duplicate the problem and found no codes in the computer. I replaced both coils on the advice of someone who said he had a similar problem, but it is still not starting after shut down when hot. My next thought is to change the PCM, but that is a big chunk of change to be guessing about. Any suggestions would be appreciated.
Now don't start throwing parts at it but do some testing when it has the problem.
First, is there spark? If no, look at he crank position sensor for going open and it's plug.
Next, is there fuel getting to the injectors?
If no, look at the cam position sensor. It times the injection.
Fuel pump failure etc.
Definately is a temp sensitive problem.
Also when it happens, is there any code set?
Effort first or you will spend lots of money before it's fixed by luck.
Thanks for the replies. When this first started I thought it was a fuel problem, too. So I have been through the fuel system completely. R&R'd the fuel filter. Pump is putting out good pressure, etc... I have not checked for spark yet. I guess that will be the next thing I do when it happens again.
You have to be prepared to trouble shoot when the failure occurs.
After it cools is just guessing but often this is the way it goes.
Try to see if spark is missing when the failure occurs.
You have to find a direction to work in.
No power, spark or no fuel.
No power means a fuse seating, a PCM relay, crank sensor etc. issue. Then nothing works.
I am going through this now with an Oldsmobile. Fails like clock work when the temperature outside is hot. It's difficult to reproduce the failure otherwise.
These fuel injection systems never vapor lock because it's a feed /return line system under high pressure. The low pressure side has either 6, 8 or 10 injectors that open so no chance of vapor lock on high or low sides.
That was the reason of my failture, the engine begin to stop anywhere at this point I just wanna put a box of TNT in the truck and make her the honors......
But I remember the same problem in a mazda so I take of the IAC Valve and was very dirty, I left the valve in carb cleaner 1 night and problem fixed.
Comment on your IAC; the reason your answer is suspect is as follows so bear with the point.
The IAC is an intake air bypass controller that controls airflow around the throttle plate for idle control.
It is electrical in operation by the computer to control idle only.
This is why the question of shut down during driving is asked.
With throttle opening during driving it has no further function and cannot shut down the motor. It could 'normally' even be unplugged 'at that time' and not cause any issue until your were to shut motor down and tried to restart when it is needed at that time, for idle control.
Since it is an electric control, soaking was not a good idea.
Now if the motor stalls coming to a stop and the IAC was stuck closed or open circuited when it needed to regain and maintain idle control. then yes the motor can stop under those conditions.
I understand you would think it was your trouble but you did something else unknown that was the real cause or was it low speed near idle stalling your referring to?
Can you see the differences?
I answer because many people read these answers and benefit from it.
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