Almost 130,000 miles on my 2000 V6, and just this morning it started acting up for the first time. Engine misfiring at all RPM levels... while idling, running on level ground, and when accelerating or pulling a hill. I believe misfire occurs on nearly all cylinders, although it may be only on 2 or 3 (certainly on more than 1). I estimate it misfires 10% of the time... for every 1000 revolutions of the crank, it's misfiring 100 times... very rough estimate of course.

Tank is 1/4 full, so I don't think I got any bad gas because it ran fine for the first 3/4 of the tank.

I'm guessing the problem is ignition related... maybe coil(s) are failing. Plantinum plugs have 40,000 miles on them.

My experience with fuel pumps tells me that could be it too, but these are hard misfires... not the type where we have momentary reduction in power.

Any ideas??

 

Are you getting a check engine light?

Have you washed your engine compartment or driven through water lately?

 

No check engine light... I hope that's some kind of clue.

Haven't been through water or washed engine.

Truck ran beautifully yesterday, just like it always does. Problem began this morning, probably about the time the engine got fully warmed up (2 miles from home).

 

Water in the spark plug holes can cause mis-fires and thats why I asked about the car wash.

I am going to guess that you have a COP (Coil over plug) going bad. My 1999 5.4L engine had a TSB to fix leaks that occur over the #4 plug (Passenger side near the firewall). I think the TSB states that a leak occurs from the heater hose going thru the firewall and drips on the #4 COP causing it to go bad. My experience is that the mis-fires occur for a while and then finally a Check engine or Service engine soon light came on.

If your engine is missing when it is at idle then pull the wire harness off for each COP one at a time (about 5 seconds) and then snap it back on. If the engine runs rougher when the COP harness is unplugged then that COP is ok. If the COP is bad and you pull the wiring harness then the engine should continue to run the same.

You should be able to do the same with the fuel injector harness's if you suspect a fuel injector is causing the mis-fire.

Good luck!

 

Bought Bosch plug wire set from Auto Zone... 55 bucks. Looks like that took care of the problem. I don't think I have the COP setup you refer to... plug wires have typical boots at the spark plug.

I really thought my problem was elsewhere. All the misfiring seemed like it had to be coming from more than one cylinder, and my experience is that plug wires go bad one at a time... not two or more simultaneously.

Live and learn. Thanks for your input.

 

Hmm... Maybe the 4.6L engines don't use COP's.

Maybe someone can set me strait on what engines and Year models have the COP's...

Good luck and great work!