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Can a coil pack work sporadically?


I own a 2005 Ford Taurus 3.0 flex fuel se with 90,000 miles. Car will run fine. Turn off engine and car will crank over but will not start for about 10 min. Let it rest and it will start.

I checked the fuel pressure was all over the gage. Changed fuel filter and fuel pump ($450.00). I am still having a problem. At times, not always, when I start the engine it will run @ about 2000 rpm?s for 15 to 30 sec and die.

I checked all of the spark plug wires for cracks and shorts. I made sure that they were secure in coil pack. After that it ran fine for about 150 miles. Then the previous problem started again. (Will crank over but not start). I checked all the connections again and it started right up.

1. Can a coil pack work sporadically?

2. Is there another filter that I may have missed?

Any suggestions will be greatly appreciated.

Michael Park

"when I start the engine it will run @ about 2000 rpm?s for 15 to 30 sec and die. "

That sounds like erratic idle air control (IAC) valve behavior, and this is not an uncommon replacement. You could start by pulling it off & cleaning it up with some throttle body or carb cleaner. Also clean & inspect the IAC electrical connection.

But that isn’t the same as won’t fire up at all. If an IAC is stuck closed its more likely to fire briefly and then die (as in your description above). When it won’t start, check for spark and then you’ll know whether to worry about ignition as well. Once again there, the first thing I’d do is just clean & inspect connections.

Yes, a coil or coil pack can be marginal and work okay sometimes and poorly others.
However, I don’t think that this is your problem. Even the complete failure of one coil (and the loss of two cylinders) shouldn’t stall the engine.

Have you checked the CMP sensor?

I think that the 2005 is a returnless fuel system. If so, did you check the fuel pressure sensor? If it’s not returnless, did you check the fuel pressure regulator?

In general, it’s hard to correctly check spark plug wires. When in doubt, replace them.

Does the 05 still have an IAC? I thought they went to throttle by wire, which uses the main (and only) throttle for idle control.

DK - the thought never crossed my mind.

To see if the trouble is fuel related spray a small amount of starter fluid into the intake and see if the engine will start up then. If it fires up then there is a fuel delivery problem. If it still doesn’t fire up then you need to check the ignition system.

Thank you. I had forgotten about the simple way to check this. I rely to much on the computer these days. Just remember what we used to do. Thank you again. Michael

Thank you. Fuel pressure fixed with new filter and fuel pump. Idid not check the CMP sensor. Will try that next.