CEL light was flashing - no code in system

[mercuryblues]

I'm not sure if it's me, or if I'm losing my head. This could be one for the Ford Panther/Modular folks...

In Southern NH last night we had a lot of rain and it was warm and humid. On the way to pick up my friend, my 2001 Grand Marquis starts skipping and bucking. After I get my friend and then head on the highway, the check engine light started to flash a couple of different times, but it never was a solid light.

So then we turn around to go back and get his car, because we're going an hour away and of course that would be the worst place for a breakdown. When we returned that night, the rain stopped. I then started up my car and it was fine again, drove it home. Hmmmm....

Figuring that it could be the infamous Modular coil on plug failure, I ordered one from AAP. When I picked it up this morning (weather was sunny and cool), I asked the counter guy if he could bring out his code scanner.... no codes, nothing. Then I went to my friend's place, tried his scanner to see if there was a fluke at AAP.... again, nothing.

To give more details about the car, it has almost 200k miles. 7 out of the 8 COPs I believe are original and the other one was replaced... I think 20k ago.

Now I'm wondering, if the CEL light does not go solid and only flashes, does that mean that it did not store a code? Perhaps it's something very minor? (i.e. bad fuel) Any help/advise is greatly appreciated. As always, thanks everyone for your help.

 

[DuckRyder]

A flashing CEL means that the catalytic converter may be damaged by continued operation.

For instance a misfire.

 

[JTK]

A *flashing* MIL indicates a misfire. You should get a code from it indicating a random or specific cyl misfires.

 

[Chris142]

Thats weird.

 

[ECUpirate]

CEL flashing indicates a misfire and possible damage to the converters due to the rich A/F mixture. You have a coil pack going bad or a spark plug problem and humidity tends to exacerbate the problem. It will only store a code when the misfire gets bad enough to point you to a particular cylinder. I had the same thing going on in my Expedition and I "re-created" the problem long enough for the CEL to remain and point me to which cylinder was misfiring.

 

[KB2008X]

As others have said, a flashing CEL indicates a misfire, and until it gets bad enough to actually set a DTC it can be quite difficult to diagnose. Even after setting a code it can still be a difficult diagnosis.

This is a situation when an actual scanner, versus a code reader, is very helpful in that it can provide real time monitoring of what the computer and sensors are reading. That's assuming the engine will act up while the scanner is hooked up. If not, you're back to guessing.

The wet weather could very well be an indicator that the problem is on the ignition side. Perhaps you could duplicate the conditions by using a spray bottle of water to mist each C.O.P. while someone runs the engine at 2,000 rpm, briefly.

 

[CHARLIEBRONSON21]

Had that problem with my old 97 expedition 5.4L whenever it rained outside. ONLY when it rained. Never stored a code. Just put up with it. Never bothered me much.

 

[Thermo1223]

I bet if you looked in the "Pending Codes" section you might have found something.

The ECU saw it and warned you about it but unless it is a more steadily occurring thing in never set a stored code. This varies by car maker obviously. My Dad's Caravan would set a code if I turned the wheel too hard I think. It is such a finicky ECU.

As was said before a flashing CEL is a misfire warning and basically if it continues you will melt the catalytic converter. Ask me how I know...