[bernsax]

This problem concerns a 24 valve ford engine.

After the car has warmed up, the engine begins to miss when idling. I don't notice it when traveling down the hi way.

I took it to a mechanic the other day but it was only a 2 mile drive to his garage and it didn't do it then.

However, after traveling several miles yesterday, each time I came to a stop, the engine missed.

I changed the fuel filter last week. It had new plugs and plug wires 14,000 miles ago. I add injector cleaner at each oil change (at 3,000 miles).

The check engine light does not come on.

If it was a problem with the injectors, wouldn't it miss 100% of the time? It is puzzling that it only does it after being sufficiently warmed up.

[smj999smj]

Fuel injector issues tend to be a lot rarer than most people realize. A regular practice of fuel additives can sometimes do more harm than good. If the additive is alcohol based, it will cause exhaust temperatures to be higher and cause the upstream oxygen sensor to give a false reading to the ECM. Many name brand fuels have additives in them, so adding more is usualy a waste of your money.

Misfires can be caused by many differant things. You could be experiencing a "lean miss." Usually a scan tool is the best aid to help isolate this type of misfire, by viewing the fuel trim in datastream mode. WIthout a scan tool, you can still check for vacuum leak sources by checking the hoses and using carb cleaner to check for possible leaking gaskets. Also, a contaminated mass air sensor hotwire can cause such a problem. Fuel pressure should be checked. The misfire could also be ignition related, as in an intermittantly faulty ignition coil. An ignition scope would be handy for detecting this type of problem. Also, make sure you installed the correct plugs; avoid Bosch platinum plugs as the tend to be problematic on many non-European vehicles. I'm not sure if the SOHC and DOHC engines use differant plugs, but if they do, it's possible to receive the wrong plugs from the parts store if they looked up the wrong plug. You can check this yourself by going online to the plug manufacturers website and looking up the plug for your car.

[clutchcargo]

I would start by checking the plug wires. I'll bet you've got a bad one.
Is this car equiped with a tachometer?
If so, does the tach jump around at all?
If so, my first guess would be the wires.

[bernsax]

Clutchcargo you are right. One of the plug wires is bad. They are only a year old with only about 15,000 miles.

The bad part is, I probably will have to buy an entire new set of wires just to replace the one bad one.

[smj999smj]

You can sometimes buy individual wires, but it is usually more practical to purchase the whole set. If one has failed, who's to say that the other's aren't on the way. I always try to get the best ignition parts I can get. For wires, I like to use NGK wires, but they are sometimes hard to get a hold of for Domestics in the US. You can get them through Amsoil.com. Otherwise, I would use Motorcraft, because they are at least as good as the original equipment.

This post has been edited by smj999smj: 11 November 2009 - 12:39 PM