I have changed the plugs and COPs with in the last 5k miles. so I am pretty sure it is not those, there are no codes being thrown.
At idle it feels like it is missing, the whole trucks shakes/shutters/bogs while accelerating and the RPMs fluctuate up and down even when I hold the throttle steady.

I am thinking maybe the Throttle Position Sensor, but I would have to replace the whole throttle body for that. Maybe my MAF the IAT always seems to be higher than they should be, by about 30-40* higher than ambient. Fuel pressure stays right around 40

I am stumped what do you guys think it could be???

56K miles
4.6L
Fresh Motorcraft plugs
Fresh Global COPs
checked the PCV
Cleaned throttle body and MAF in the last 2k miles

 

I'd recheck the global COP's 1st....might have had a couple go bad

 

I have gone through and unplugged all of them one at a time while running and each time the idle got worse Maybe there is a vacuum leak somewhere? i unplugged the EGR and no change in idle

 

Disconnecting doesn't really tell you anything in this case, - other than you don't have a dead hole. On board diagnostics WILL tell you that much anyway. Lacking coils that aren't firing right are just that, -"lacking". Inferior, inconsistent, intermittent, -what ever you want to call it. They fire that way due to shorted turns in the windings and will cause ignition havoc. So, they usually just don't die. They mess with your head and promote hair loss.

 

I'm having the same problem with my 01. It just started running rough. I dont know where to start, plugs , coils, fuel,,,, any suggestions

 

engine..., mileage, maintenance?

 

I'm having a similar issue, so I figured I'd just toss it right into this thread, rather than start a new one.

I have a 2000 F-150 w/ 4.6L + automatic. I recently purchased it with about 195,000 miles for use as a work truck. It appears to be running fine at idle. Periodically, it runs very rough between 40-45 mph - I can feel a pronounced vibration/bucking all the way up through the steering column and wheel. It also produces this same sensation at faster highway speeds, although infrequently, and it disappears after about a minute or two. When I experience it at 40-45 mph, I am usually able to accelerate through the bucking/vibration. It appears to be independent of the transmission, as it shifts in this speed range and the vibration does not disappear. Also, sometimes it feels as if the vibration occurs during deceleration between 40-45 mph as well. Additionally, I only notice the vibration when the motor is hot and has been running for some time; I've never experienced vibration after cold start. After a cold start I can accelerate up to and through 40-45 mph smoothly.

The condition has not thrown any engine codes. I did have a P0420 code (catalyst efficiency bank 1) but I had a muffler shop inspect the cat on the passenger side and they determined it was not clogged. I've since stacked a couple non-foulers in the cat to back the 02 sensor out, and haven't (yet) had a relapse of the code.

My initial thoughts were ignition. I started by changing spark plugs. I removed premium Bosch plugs that appeared in good condition (no fouling) and due to the effort involved, I went ahead and replaced with the recommended Motorcraft plugs. I've replaced the coils with new Accels. I have not noticed any arcing over the coil wires and my wiring harness appears in good condition. I installed a new fuel filter. I've inspected the injectors with a stethoscope and tested them for resistance (all read between 14-15 ohms after running for about 5-10 minutes, with the exception of the #8 injector which I could not access). The injectors all ticked, although a few sounded maybe a bit duller. I reset the PCM and ran the truck as recommended in the owner's manual. I've also run a can of seafoam through the fuel system.

None of what I've done has lessened the vibration though. I'm curious to know if anyone has any insight, particularly regarding the injectors, or encountered this particular issue before.

 

When someone mentions bucking on accelleration, the first thing I think of is a clogged fuel filter.

 

2 mistakes:

Do you have coilpacks/wires or COP?

Seafoam eats cats, Techron is the only approved additive.

 

COP - the old coils were probably fine. From what I understand coils don't necessarily throw codes if they are failing or intermittently faulty.

Don't really care about the cat. The truck has nearly 200,000 miles on it. If it don't rattle, its fine. My state does not have an emissions check outside of checking for exhaust leaks.

I'm amending my previous post, the vibration occurs between the speed range of 35-45 mph with consistency.

 

People haven't really had very good luck with Accel cops in the mod motors.

You may want to pull the plugs back out and do a compression test.

 

If the hesitation occurs between 35-45 (light to medium throttle?) than it is almost %100 a misfire somewhere. If the misfire is low grade it doesn't really show up until that speed. It should shift into OD around 40mph so when it does lightly start pushing the gas and you will probably feel it buck pretty good. If you just did the plugs it is probably either the wires or coils. I hate electrical gremlins...GL

 

my check engine light finally came on so i had it checked at auto zone and it said it had a mis fire on # 2 . i change the coil and plug and runs good as new. i have a question about the accel coils, are they good? i found a set of 8 on ebay for 180.00 .

 

No. Accels don't have a very good reliability record.

These are OEM:

http://www.ebay.com/itm/New-Visteon-...2fa4a1&vxp=mtr

These supposedly are reliable:

http://www.ebay.com/itm/FORD-4-6L-5-...11%26rk%3D2%26

 

Replaced spark plugs
+ filters fuel/air
+ spark wires
Then thought fuel additives were working, then maybe only when cold this worked
Then upgraded the gas by topping off w/premium, OK when engine cold, not when warm/hot
Fed up - went to AutoZone for free scan (no codes sent out)
Went to NAPA for free scan - they used 3 scanners (no codes sent out)
Neither could guess what it was

Finally went to local mechanic - they replaced the coil (2 of the 6 were not firing) - in less than 4 hours. Parts/labor costs spot-on with my research. Now it's a little sports truck again, wants to speed.

2001 F150 smallest engine, no frills, Red