Stalls!

[Gandolf]

2001 P71 118K.

Car dies while running, will not restart unless you 'cycle' the key to off first. (in other words you can not just twist it to the start position).
I noticed that the fuel pump continues to RUN when this happens!
This only happens when it dies and can not be duplicated by doing things like unplugging the Crank sensor while it was running.

1.New Computer
2.new motercraft plugs
3.new fuel filter

I bought this car like this, the dealer who had it was about to install a new computer when I bought it as is. However I had him ship the new computer to me and I installed it, no difference. It does not have any codes in it and the check engine light does not appear when this happens.
It will do this at anytime but hardy ever once the car is at normal operating temperature. It will do this in my drive way or on the road, just never know when?
I noticed that when it happens the temp light comes on briefly (but it is not hot) I have noticed that the radiator fan will sometimes come on when it is cold, say two minutes after starting but seldom?
If I had DBR 2 streamer I could read the problem in real time.

A little about myself, I am retired from the auto industry, spent 25 years as a tech. (foreign cars). I am still Master ASE certified and I taught Auto tech at the College level (6 years).

However without the proper test equipment and the fact it is intermittent, I am posting here in hopes of someone experiencing this type of problem and save me the time doing scratch and sniff!!
Thanks

[ModMech]

I would imagine that either the crank sensor (or wiring) or the IAC solenoid are the cause of this. My bet would be the IAC.

You did not specify if it was at idle, or while driving. That would change the diagnosys completely as the IAC will not cause it to die while driving, only at idle.

[dzus]

> Things to check: fuel pump pressure,vacuum at fuel regulator or a faulty fuel pump relay. Check the relay part #'s in the relay box because some should be the same and can be swapped around to see if that's the problem.

[Gandolf]

Here is what I have determined so far;

It looks like the Cyl. head temp sensor is the culprit, based on previous observations.

If the CHT sensor conveys an overheating condition to the PCM, the PCM would then initiate a fail-safe cooling strategy based on information from the CHT sensor. A cooling system failure such as low coolant or coolant loss could cause an overheating condition. As a result, damage to major engine components could occur. Using both the CHT sensor and fail-safe cooling strategy, the PCM prevents damage by allowing air cooling of the engine and limp home capability. For additional information.
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The CHT sensor:is mounted into the wall of the cylinder head and is not connected to any coolant passages.

It sends a signal to the power-train control module indicating the cylinder head temperature.

— If the temperature exceeds approximately 121ºC (250ºF), the power-train control module disables four fuel injectors at a time. The power-train control module will alternate which fuel injectors are disabled every 32 engine cycles. The four cylinders that are not being fuel injected act as air pumps to aid in cooling the engine.

— If the temperature exceeds approximately 166ºC (330ºF), the power-train control module disables all of the fuel injectors until the engine temperature drops below approximately 154ºC (310ºF).

l If the engine reaches critical temperature, the following happens:

— The coolant temperature gauge pointer will read fully hot at approximately 121ºC (250ºF).

Bare in mind that I am NOT experiencing any overheating, however I believe the Cyl. head sensor to be defective. One is coming tomorrow.

[Gandolf]

Originally Posted by ModMech

I would imagine that either the crank sensor (or wiring) or the IAC solenoid are the cause of this. My bet would be the IAC.

You did not specify if it was at idle, or while driving. That would change the diagnosys completely as the IAC will not cause it to die while driving, only at idle.

"It will do this at anytime but hardy ever once the car is at normal operating temperature. It will do this in my drive way or on the road, just never know when?"

Thanks

[ModMech]

Crank sensor or wiring (conector to it).

[Gandolf]

The head sensor was broken!! The whole upper plastic casing was completely broken, only the wires keep it together. From the looks of it, it has been broken for a long time. It runs a lot better now, we will see in the days to come.

[dzus]

Good deal!

[Gandolf]

Crank sensor was Kaput also. Replacing it stopped
the weird running problem through warm up! Damn what a POS this car was (just kidding) I like this stuff, did it for 25 years. Someone spent a fortune throwing parts at this car. Two control units this year, probably never needed one?
To this point I have replaced the plugs $20.00, only because they were the wrong ones, Cyl. head sensor $7.00. crank sensor $13.00.
It is not fixed yet !! I have one or more COPS or insulators bad. I have a used one coming and a complete new set of springs and rubbers:-). It has some tip in stumble under load (slight load in overdrive at slow speeds, you know) and some misfire at higher rpm. More to come.

[Gandolf]

#8 coll on plug was Fubar