Here is a tip to help locate the trouble, based on my experience on a 99 F150 4.6 (No COPS; Modules) with a low grade, classic lean, miss under light acceleration/deceleration I have been chasing for the last 100K miles.

I have been thru almost every thing on the engine looking for what the cause was.
I changed plugs (twice), wires, coil packs (both), verified vacuum lines for leaking, TPS, Air charge temp sensor, (and a few more) you name it. Each time I worked on it, it would go away for a couple thousand miles, but ultimately return.

It finally began to set some sporadic codes for the Cat efficiency on bank 1. Changed both 02 sensors and again no real help. But, What it did do was steer me to do a deatiled look at bank 1 cylinders.

After looking at the downstream O2 sensor readouts, I began to see a pattern of an occasional voltage drop to 0 volts. I pulled each injector wire off, one at a time, and each time I did this, voltage dropped to 0. From this, I deduced what I was seeing was the misfire.

Knowing that changing the plugs again was only a temp fix, I was now fairly sure the root cause was a bad injector(s) taking the cylinder(s) lean and eventually damaging the plugs.
I bought 2 replacement injectors and took my best guess (cyl 3-4), and replaced them. While at it, I removed, cleaned and swapped 3 of the 4 plugs (1-3) around (marked both old injectors and plugs to identify where they came from).

After 200 miles driving things got real interesting. It developed a really severe miss and finally set a code for cyl 3 misfire. Since this cyl had one of the new injectors, I knew the plug was bad. I also knew what cyl it originally came from, so now that original cyl injector was suspect. Swapped out that injector with one of the 2 old on hand, replaced all of the 3 original plugs and started to really look close at the Bank 1 rear O2 sensor readings. still an occasional drop out, so I knew I still had a bad injector somewhaer. Continued swapping them around till the readings leveled out.

After about 500 miles now, it runs better than it eved did, no codes, and not even a hint of a misfire.
Moral of the story, I had at least 2 marginal injectors. Use the rear O2 sensors to determine what bank the misfire is on, and go from there. Even if you do not feel the misfire, the rear Cat O2 sensor will see it as a high Oxygen content in the exhaust stream.
If your scanner also supports fuel trim settings, look to see if the long term trim is high/low. All the material online suggest a deviation of +-10 is acceptable, but in reality anything over 3-4 is a indicator of something amis. High positive settings indicate a chronic lean compensation, high negative settings indicate a chronic rich compensation.

Chasing this one down I learned a heck of a lot more than I really wanted to. This was my first bad injector diagnostic, and with limited test equipment available, was a real bear to track down.

Dialtone

 

Altho this isn't the technicians way for a person with limited experience and knowledge this shadetree method should work. You'll need an assistant. Have your assistant start the engine and put the trans. in reverse with E and foot brake applied and add a little accelerator pedal to load down the engine. You start unplugging the connectors to the injectors and COPs one at a time. Plug back each connector after it has been tested before you move on to the next. You should notice a drop in RPM(have your assistant watch the tach for a change as you remove each connector) and the engine should shake a little(you've created a misfire) if that injector or COP is functioning properly. If the RPM doesn't change and the engine doesn't shake a little that injector or COP(or associated spark plug) is already causing misfires and needs serviced. Pulling the fuel rails makes getting the COPs out a lot easier. With your high mileage you should change the "O" rings(inexpensive) on the injectors before you put the fuel rails back. If you can get 8 COPs for $100 on Ebay(and you trust them) you don't need to waste your time doing this test. Just go in there and start swapping parts. Personally, I prefer to pay $40 for them and get a lifetime warranty which I doubt you'll get on Ebay.

 

Reminds me of the 01 F250 I bought on ebay. Bought it cheap,and after trying to get it shipped 680 miles home and being jerked around for a month, i gave up and my son and I drove there and picked it up in person. Ran smooth for the first few minutes till it heated up. Then the miss began. No codes, and I drove it home with it gradually getting worse as we went. Stayed the night in a motel, and next morning, smooth again till it warmed up. Felt like it was starving for fuel. Got it home, and the next day looked underneath and found it had a brand new fuel filter, so some one thought similar to me. Ended up having the codes read and there were 2 cylinders with misfire codes stored in the computer. Installed 2 new cops and 30000 miles later still runs great. It did eat a
3rd cop a year after the initial fix when the truck sat a few days and the weather was very foggy and damp. Had that read and changed the 3rd cop and all is well still.

 

I have had a lot of experience of useing the F150 4X4 and have probably driven more than most. My job with Goodyear selling Off Road tires has taken me over 50,000 mikes per year on strip jobs from VA,KY,and WVA. I worked for a total of 27 years so that is a lot of miles, plus I own a 2001 F150 XLT Off Road Towing package vehicle now. In rough conditions like I used mine, I stated getting the "Flutters" after about 50,000 miles. I always took it to the local Ford Dealer and had them check it out. They pumped the transmittion fluid and changed the filter and that would take care of it for another 50,000 miles. I always drove my Fords for almost 200,000, about 4 years and never had the first Valve cover off! I went through a lot of u-joints and brakes but never a break down. If you have used it hard-pulling a boat or camper or just hot rodding, I would have the transmittion fluid pumped out-to get what is in the cooler out and see if that takes care of it. I am no mechanic but I do know a litle about Ford Trucks!

 

It's not that simple. You can't change your transmission fluid and expect misfires to disappear. It's too bad it doesn't work that way, but it doesn't. Ford trucks are know for misfires(bad COPs), EGR problems(cracked rubber hoses and clogged EGR ports) and lean codes(more cracked rubber hoses). No amount of transmission fluid is going to solve any of those problems. Don't mention the 07 and newer V8 3 valve with the 2 piece spark plugs. Shops charge $500.00 to start the job and $150.00 for each plug that breaks and many of them do. You better have $1,000.00 handy if you want to change all 8 spark plugs on those things. You tube is full of videos showing you how to get those plugs out without breaking them. Sometimes you get lucky, but the last one I did 6 broke. We ended up having to break #4(farthest plug back on pass side)to get it out because the hex portion the socket goes onto was spinning inside of the sleeve at the bottom and would not come out. Breaking it and removing it with the Lisle tool was the only way to get it out.

 

I wonder if the OP ever got his issue fixed from 11-29-2009, an old post?
He never came back and told about it.

 

I'd be curious to know the fix too. I went back and read the post Dialtone made which I had somehow skipped over previously. You can't argue with success, but we need to know how the cat works so we can draw the correct conclusions about what we see from the O2 waveforms. Cat efficiency is the ability of the cat to store oxygen. If you watch the post-cat O2 output it will run about .8Vdc(most manufacturers, but not all) until it can no longer store any more oxygen. When that happens you see the waveform drop momentarily to near 0 volts and then pretty quickly spike back up to postitive voltage when the ability to store more oxygen has been restored. When you pull a plug wire YOU create a mifire. You dump raw fuel into the cat. That's BAD cat food. You will kill the cat with raw fuel if you don't do something about it. The sensor dropped to 0V because the ability to store more oxygen was exceded when the misfire was created by pulling the plug wire. It is NORMAL for the voltage to occasionally drop to 0V as was seen before plug wires were removed. It is also NORMAL to see the voltage drop when plug wires are removed(a misfire has been created). Misfires are NOT NORMAL and cause the post O2 sensor to react which is also what it is supposed to do with a severe misfire(plug wire removed). After all the parts swapping it was NOT a problem when Dialtone saw the post-cat O2 sensor drop to 0V once in a while(that's what is does when it is workng normally and has reached the max ability to store oxygen). Dialtone saw this as a problem which it wasn't and moved a lot of parts around. I'd bet if he got his scan tool out today and watched the post-cat waveform he'd see it still switching from .8 down to .2 occasionally even WITHOUT a misfire. The injectors on the Ford trucks are really very reliable. The COPs are not. The plugs foul because of the bad COPs and cause mifires. Ford doesn't like to set misfire DTCs. You need to go to Mode 6(E Scan Pro is the very best at Mode 6). You'll see misfire counts on all cylinders in Mode 6 on E Scan Pro even with the MIL is NOT illuminated. When I have a misfire, but the MIL is not turned "ON" I go to mode 6. Bernie Thompson created a winner when he came up with E Scan Pro. If you fix Fords you need E Scan Pro.

 

Concerning the rear seanors, If there is a code 420, the PCM stops looking at them after so many attempts and you will see zero output when looked at with a scanner.
Once the PCM is forced into re testing all PIDS the rear sensors begin to be monitored again until too many failures are counted then goes back to zero.
The PCM abandons them because the output is no longer usefull.
I saw this on my truck before I had a chance to replace one side cat assembly.
After replaceemnt, no 420 code and the rear sesors never stopped working again.

 

That's odd! I must be in a diesel section. I have never had a 1997 -2001 to ever misfire in the Gasoline models! Up to almost 200,000 mile in rough service! I also have never heard of a diesel having spark plugs nor any thing having dual plugs, but I am not a mechanic-only a driver trying to get enough post in to sell mine that I am no longer able to get in and out of!
Sorry!

 

Diesel is different from gas using very high compression(compared to gas) and no ignition system(not needed due to high compression causing combustion). I didn't know the rear O2s would stop functioning once you get a P0420(cat inefficiency-basically clogged cat). I'm going to monitor one the next time I see a 420. I guess they could do that since the cat isn't going to fix itself once it goes bad. I did see a guy on You Tube wash on in soap and water. He claimed once all the debris was rinsed out the cat worked. Who knows. The main thing people need to know is if you do get a P0420(bad cat) that happened for a reason. Cats don't just go bad without help. If you change the cat WITHOUT fixing the problem that killed the cat in the first place you may end up with another dead cat. Very expensive.

 

Hey yall.
Welp, been doing alot of research over the last year or so. I have an 02 taurus that jerks really bad. No codes. No noises. Nothing. I bought an 03 ranger edge 4x2 about 2 months ago. Same thing. FINALLY, i found a video that explained the same exact thing that my car and truck was doing. They hooked it up to a computer and show you what is happening. It is the cam syncronizer assembly. Bushing goes bad and the magnetic tooth hits the sensor and causes the injectors to pulse. Look it up on youtube. Type in cam sensor trouble. I havent replaced mine yet, but im about 95% sure thats it.

 

Through all the thread replies there was a lot of trial and error done.
If a Scanner is used to look at the cylinder misfire monitors, the cylinder with the high misfire counts will be seen.
This eliminates at lot of guessing and trials, swapping, time and money wasted.
What causes the shudder/flutter is a coil with shorted turns.
This condition never causes a code or a CEL light because it's not a hard fault but comes and goes with driving conditions.
The no code reason is the computer sees the misfire when it occurs but cancels the record when is clears (not a hard fault).
.
There is still a record of the misfire, but saved in a different part of memory that has to be accessed with a Scanner to see it and has no ability to set a code or CEL light from that memory location..
Good luck.