I JUST bought my 2001 Expy (5.4 with 60k miles) and seem to have a small problem. This is my first Ford Truck, I traded in my Dakota for it!

While driving at a steady spped anywhere from 40-50 mph, the engine acts like it sputters or chugs. If I accelerate, it seems to go away, it also doesnt do this at highway sppeds of 60+.

ONLY if I go the same speed, any where in the ranfge of 40-50mph.

Years ago I had an 83 LTD that acted the same way, and it was a corroded distributor wire that was making an intermitant connection. I dont know much about the newer 5.4s.

Any suggestions before I take it in to the shop?

 

no distributors on these, they have COPS. i would check all 8 of them, check the wires, the connections, make sure they are all plugged in and screwed on properly. Maybe the wiring is frayed on one or the COP has come loose somehow. If you really want to take a good look and take them all off, you may as well change the plugs while you're at it.

 

Change the transmission fluid. Trust me.

 

Take a look at the engine RPM while this is happening, bet it's unusually low. The engine might be lugging because the torque convertor has locked up a bit too early. I concur with hkiefus.

 

WOW -


The transmission fluid was the first thing I was going to do anyways!
I am dropping it off at the dealer I bought it from, since I have only had it a week, and it came with a minimal warranty.

On test drive I made sure to go highway speeds, never noticed it in the test drive. I hope it is a small a deal as tranny fluid.

 

Car is at the dealer now for them to take a look. The service manager said he was pretty sure what the problem was, something about each plug having its own idividual coil.

Sorry for my ignorance, but what is a COPS ??

 

I believe it stands for "Coil On Plug". Instead of having one coil and a distributor, you basically have 8 coils, one on each plug. Its possible that one of yours is crapping out and going to need to be replaced.

 

Thanks for all the advice here, I just talked to the FORD Dealership, they found the #8 coil was bad, they replaced it.

I asked how much, because I bought this car used from them last week, no warranty to speak of, they said "No charge, you've bought 3 cars from us, and had this one only a week, its on us."

I thought that was pretty cool, they could have charged me a $100 deductable of even full price, depending on how you classify the repair, as engine or electrical.

 

If that doesn't do the trick, make sure to change that transmission fluid. I'm awfully suspicious of a COP diagnosis/change with it having a code set/read.

 

Just because a light didn't set doesn't mean the coil wasn't faulty or weak...I had an expy 5.4 roll through about 6 months ago, had 3 bad coils and almost a dead skip and the computer did not pick it up. Even the Mode 6 data showed no misfire malfunctions in the motor.

 

I have to admit, the COPS are making me nervous (no pun intended).

I do not know how I would diagnose these if I have another one fail, nor do I know exactly how to fix it.

Checking at a local autostore, I can get a replacement for about $50, but if the symptom arrises, I would not want to replace all 8, that is like shooting fish in a barrel!

 

That's why I was hoping you could get a code. That would indicate which cylinder was in question and then you could move that COP to another plug and see if the problem moves around.

AwesomeBullet seems to have a case where the computer wouldn't pick up a misfire. Perhaps he could give us some advide on determining a bad coil in the absence of a 'light'.

 

The best way I have found to determine a faulty coil is using a labscope. Place a low-amp inductive probe around the signal side of the coil harness and watch the waveform. It should ramp up very sharply to a high peak, then drop just as sharp down to about halfway between the starting voltage and the peak voltage. It will stay at this voltage for just a millisecond or so, then drop back down to the starting voltage. If the coil is bad, sometimes it will have a double peak or the ramps will be gradual, not steep like they should be. What you are watching on the scope is the buildup and collapse of the magnetic field in the coil. The signal that is being displayed if the coil is bad is interference on the feed wire backfeeding back to the ECM. The only coils I see on a regular basis fail are numbers 4, 3, 1, and 8.

On the case of my multiple failure Expy, even the scope didn't pick up one of them. Replaced two of the faulty ones and still had a skip under acceleration. I ended up having to do trial and error, I knew I had one more bad one but didn't know which one. So I got another new coil and just started swapping it out with the 6 originals still on the vehicle until I finally located the last bad one and the motor ran smooth as silk.

The coils you purchase from AutoZone (if you get a Wells coil) are actually the same part you would get at a dealer for a lot less $$. Many times the one in the box at AZ will even have the Ford sticker and part numbers on the top.

 

The guys at the shop today said the WDS could also pick up a bad coil even when the PCM could not. I would have thought the used the same approach (crankshaft acceleration between firings) but perhaps not. AwesomeBullet's approach seems from the electronic side. Here's a man that knows the meaning of true diagnosis.