Possible Clue

Now that I'm concentrating on it I had a similar problem with my '79 Toyota which is carbureted.

It has a solenoid valve called an anti-dieseling valve or anti-backfire valve or I just call it a shut-down valve. Well long story short the computer has a glitch in it that causes that solenoid to open and close giving grief. I fixt that by cutting the wires, then wiring it directly to the battery with a dash switch isolating it from the computer.

Then to start I first turn on that solenoid and then start the engine. To shutdown I turn off the soleniod then the engine. If the engine is running fast like at fast idle, shutting the solenoid off has no effect because it merely shuts off the fuel idle circuit.

Similarly, when cruising at part throttle, the fuel idle circuit is/may be used or at least is not totally dominated by the high speed fuel circuit. If, while cruizing, this valve gets shut off the engine will sputter. Goosing it cures the problem temporarily. It caused a problem during shifting too (manual shift) because the throttle gets eased during the shift.

It starts OK with the valve shut off because the throttle is advanced a bit during start - especially on a cold start.

So!!

This is exactly how the Crown Vic acts. Does it have a shutdown/anti run-on solenoid or similar contrivance? Could the Ford computer have a similar glitch? If so why wouldn't it show up in the diagnostic codes? Where would that valve/contrivance be located?

You may have an ignition problem. Below is a list of things to check.

1. Spark plugs. Do these have more than 30,000 miles on them? Inspect their condition.

2. Spark plug leads. (Do you have spark plug leads or do the coils sit on the plugs?) If present, check the plug wires for resistance, preferably after the wires are hot. A spark plug wire may read ok cold then go high when hot. The symptom: Starts ok, then 10 miles down the road begins to misfire with minor load increases on the engine.

3. If you have coils on plugs, these run quite hot because of being on the spark plugs and the high tension sides are known to break down. I found one on a Ford used car lot last summer. The salesman tried to sell me Ford Escape that had a bad coil (on Plug). It started ok, but a short test drive showed misfiring. Too bad - I was ready to buy the vehicle before this happened. I walked away. I got a call later in the day saying they had found the problem and fixed it. I did not go back as I had already shopped other dealers and found something else. I wondered why the vehicle was on the lot for sale when it had an obvious problem and was simple to fix. Did they miss it, or were they trying to move the car without fixing it? Who knows? My trust fell on that salesman and the dealership.

Welcome to my world. I deal with a reported vehicle problem similar to this on almost a daily basis. Most of the time before they get to me they usually have already had a few hundred dollars worth of parts thrown at them.

First order of business is to figure out what you are losing. Even the "no codes" is a clue. Inside the repair industry techs are very much left to find their own way. Call it the price to be paid, for the money saved when people use discount tire stores ect. To that end, there really are very few techs that can afford to invest the time and effort to learn how to diagnose your car's problem, let alone invest in the equipment to support the effort.

Here is the routine that must be followed. First how often does it happen and under what conditions? You actually started to describe it occuring when the car is hot, and that is great. Now lets really narrow it down. How far must the car be driven for a tech like myself to expect that I would experience a failure event? How long of a time will the failure event last? Does the car restart right away when it dies? Does it die while cruising down the highway, or while slowing to a stop? Does it die when accelerating? Does it happen randomly in any or all of the previous conditions?

You started talking about disabling the decel or anti-diesel solenoid on the Toyota carbureted car in your second response. Throw that information away, it has no bearing on what the Crown Victoria is doing now. When someone tries to make a comparison like that I call the outcome "Tainted Intuition". If you would show up here at my shop with your car, and lets say you already replaced a few hundred dollars worth of parts, I would stop you from telling me what you have already done. I don't want to know. The reason is you may have easily built a second (or maybe even a third) problem into the vehicle over top of the first one, and the challenge the public holds pro's to is to actually find not only the initial problem, but to not let any others slip by undetected as well, even if the owner is responsible for adding the problem! If I start with a fresh perspective, I won't succumb to the habit of assuming that the "XXXX" sensor is new and it was doing this before it was replaced, so it cannot possibly be the problem. The truth is, it absolutely can still be the problem for any number of reasons.

There is a very logical routine that must be followed for every diagnosis, the problem is many don't see what routine to follow until after the problem is found, if they even actually see it then. That's one of the most difficult classes that I teach techs today, how to use a more logical, strategy based routine to perform diagnostics in an efficient manner.

So here is where you take your first step. Why is the no code actually important? Name a couple things that could cause the vehicle to shut down without the computer detecting the shut down that occured was a problem.

When the shut down occured, again how long does it take to re-start the engine? This gives me a chance to predict how much time I actually have to perform the diagnostics during each failure event.

When shut down occurs are you losing fuel? That could be from fuel pressure loss, as well as injector trigger.

What about Spark? Spark is measured by the ignition systems ability to jump a tester that requires 25,000v to jump the gap, not just from a wire to the valve cover..

Are you losing both spark and fuel?

Does your check engine light come on as soon as the car quits?

Does the check engine light NOT come on when attempting to restart the car?

Can the imminent stall be prevented by using the throttle, in the event the stall occurs during decel.

This vehicle does have scan data even though the PCM isn't setting a code. Scan data will report trends which are used to see if the computer is compensating for some type of a problem. What are long and short trem fuel trims at idle, cruise, moderate accel, and decel?

What is the reported spark timing under those same previous conditions?

What is the scanned BARO reading, and what altitude are you at?

What are the IAC counts?

That's the start. There are no silver bullets to kill this gremlin. You'll have to learn how to work through this just like a tech does. Oh BTW. If you take more than one crack at this imagine what you (or others) would be saying about a shop that didn't fix it the first visit. Picture yourself in a shop and this car is sitting in your bay, for the second, or third time. Now you have to figure it out and fix it, and you not even going to be paid for the time that you spend because you guaranteed it would be done right the first time!

So! I'll take it to a shop and tell em the engine is cutting out but doesn't die and the problem started after the spark plugs were changed. It happens at constant throttle and more hot than cold and generally uphill. Then keep my mouth shut unless they ax me something.

Thank you both - this is what I meant for a start - I wouldn't touch the dam thing myself.

When you take it to the shop, concentrate on the symptom occurance details as I outlined above. They need it to act up in order to identify the problem and test for the source. The better you describe the conditions it occurs under, the easier it will be for the shop to diagnose and repair it.

Yeah OK 10-4 Will Do ON My Way

As for the Toyota you might be amused - I couldn't find the problem with my amp/volt/resistance meter (storebought) or continuity checker (homemade). One shop couldn't find it with their fancy equipment so I bit the bullet and went to Toyota and axt the parts man what might be rong, because as we all know parts men know everything, and he sloughed me off on the service manager, who, as we all know has many years of experience and really knows everything, and he was stumped and just then here comes a KID walking by, must of graduated from high school yesterday, and I got sloughed off on that KID and the KID said the computer was causing the shut-down solenoid to act up - replace the computer - I did ($200) and it worked. 10 years later it happened again so I did my thing with the workaround. Neither I nor the parts man or service manager or the shop even knew that '79 Toyota even HAD a computer. Took the KID 3 seconds. :-)

It was the spark plug wires. Plugs got changed at the standard 60K service 10K miles ago. Not a word in the owners manual or maintenance schedule about the wires. Well I shoulda known but just assumed they musta gone to some exotic new material that didn't break down (like copper).

Seems to me Ford would have said something. But you turn your heap in to the "service rep" who has 4711 other cars in line and he writes it up and turns it in to the mechanic who does exactly what's wrote up (which he is sposed to do, of course) and can't waste any time calling the rep to call me just because maybe we should....etc. and they actually do a pretty good job overall but once in a while it seems to me there is a link lost and a smidgin of control over the fate of your own heap.

So I put in the finest sparkplug wire set I could find for $132.75 including tax. $167.45 labor. Not too bad considering they checked it all out and if it had been something else I couldn't have found it myself. About the same as Ford would have charged at the 60K service so it really didn't cost me anything did it?