Hi Fellow Ford Fans,

My 2001 Supercrew with 68,000 miles all of a sudden developed an acceleration stumble. The engine idles smoothly. If I accelerate with a light foot, no stumble. If I accelerate with a heavier foot the engine has a really bad miss/stumble. If I accelerate really hard, it smoothes out.

I changed the fuel filter out at 60,000 miles and about 100 miles ago put a can of Berryman B-12 Chemtool fuel system cleaner in the tank, but it hasn't improved any. I've not run the truck in water or washed the engine ever. I got a "Check Engine Soon" warning light just after the stumbling started and so I disconnected the battery for 30 minutes, but all that did was reset the computer and turn off the warning light; the stumble remained, however.

Before I'm forced to take the truck to the dealer, anyone have some suggestions I can try at home? I used to work on all my pre-fuel-injected cars (good old days, the carburetor!) on my own, but I don't have any diagnostic equipment, and so can't read the codes.

Any clues would be really appreciated,
Jack

 

Hey brownbear13 have the trouble code pulled and post the code, it's easyer to pinpoint the problem that way so your not changing out unnecessary parts.

 

Hi Jack and welcome to the forum

Like karenj said you need to get the codes pulled and see what shows up. Chances are pretty good that you have a P0*** code which is for a misfire. The code should point you to which cylinder caused the problem. A P0301 is cylinder #1, a P0306 is cyl #6 etc. The common causes of a misfire are a bad spark plug or COP (Coil On Plug).
If you have an Autozone close by they will scan it for codes for free.

 

Hi Karenj and Dave,
Thanks, it's good to be here. This is by far the best place I've seen for information about Fords. I'll try to get by my local Autozone today and see if they can scan for codes. I really appreciate the tips and I'll let you know what I find.
Have a great day,
Jack

 

One thing I forgot to mention is that it seems that Autozone wont scan it if the light isn't on. You may have to drive it enough to have it turn back on.

 

Hey Dave,

Yes, you are correct, sir! I went by Autozone and they said the "Service Engine Soon" light had to be on to read the code. We plugged in the diagnostic tool, but it came up blank. I shouldn't have disconnected the battery and reset the computer. Now, I've got to wait for the warning light to come up again. It's always like that isn't it? I'll keep you posted, but it's gonna be a waiting game I guess.

Thanks,
Jack

 

Hopefully you won't have to wait too long for it to show up again.
If you get tired of waiting you can take it to your dealer and they can do a cylinder power balance test on their WDS scan tool. Usually a miss shows up pretty easily on it.

 

I had what sounds like the same problem and the Ford scanner said that my spark plug wires were breaking down under load. 1998 F150 4x4 auto with 4.6L.

 

Thanks for the last tips from Dave and 2001gocougs. The "Check Engine Soon" light still has not returned, but the engine stumble continues. The spark plug wires breaking down is interesting. It wouldn't seem like my truck wouldn't be suffering from that with just under 69,0000, but only a Ford diagnostic machine could probably tell me more. Any idea if Ford will do the diagnosis for a flat rate if I tell them I'll do the repair myself? What's the going rate for a diagnosis? I live in Austin, TX, by the way.

Have a good one,
Jack

 

A 2001 doesn't have spark plug wires. It uses COPs (Coil On Plug). Each spark plug has it's own coil sitting on top of it. These do go bad sometimes though. First thing you need to do is determine which cylinder or cylinders the problem is on. Without a code or doing a power balance test you'll just be guessing. I always replace the plug first as it's cheapest and then if that doesn't cure it then it gets a COP.
At the shop I work at we would charge an hour to scan it and do a power balance. You can tell them that you just want it diagnosed and then they can give you a quote.
If you don't like the quote just tell them you'll fix it yourself. You may want to tell them that if they haven't figured it out in an hour to stop. Tell them that's all you can afford or something.

 

Hi Dave ,
Okay, I went to Autozone and they saw code PO306 which, of course, and like you correctly interpreted , is a misfire on cylinder #6. I changed the plugs (68,000 miles) with the correct Autolite plug, but the condition remains the same. Do I move on to replacing the #6 COP? Is there a way to test for a bad COP? By the way, how are the cylinders numbered on my 2001 4.6?

From what I can tell, the stumbling feels quick and erratic, so I'm thinking it's electrically related, for what that's worth. When I replace the plugs I gapped them correctly (.052-.056), used anti-seize compound on the thread, and an electrical grease on the plug tip and white porcelain part of the body so the COP boot could slip on easy and keep moisture out.

Any clues would be appreciated,
Jack

 

Unless you can watch the power balance on a scan tool while it's missing probably the only thing you can try is a new COP. I suppose you could swap #6 COP with another one and wait for the light to come on, get it scanned again and see if the misfire followed the COP. That would be a bit of a pain to do so you might just want to buy a new COP.
The cylinders are number 1-4 on the right (passenger's) side, 5-8 on the left side.

firewall
4 8
3 7
2 6
1 5
radiator

 

Hey Dave,

I'm going to swap out the #6 and #2 COPs since those are the easiest to get to and have the scan done again at Autozone. I'm hoping it's a COP problem so I can be done with it. I'll be sure to buy a Motorcraft COP, though. Autozone only carries Wells brand and I'd rather stick with OEM parts. Thanks for the great advice as always, Dave.

I'll keep you posted with the results,
Jack

 

Hi Guys and Gals,

My 2001 Supercrew is my first 4.6 fuel injected truck previous to that it's been all carburetors with conventional plugs, wires, caps and rotors. I just ordered a Motorcraft COP to take care of #6 cylinder and will have it in a few days. I changed all the plugs (Autolites, some were tricky to get to, but not too difficult) and was wondering if I was supposed to have put dielectric grease on the insulator and TIPS of the plugs.

The grease packet has a drawing of where to apply the grease and it shows placing it on the insulator of the plug AND tip. Is this the standard practice? I would think that you would diminish the electrical contact between the boot and plug. I would have no problem going back to clean the plug tips and contact shaft of the boot if you think this is necessary.

Just wondering,
Jack

P.S. There's no going back to carburetors and caps and rotors. Fuel injection all the way!