I have an '01 %-150 with the 5.4L engine. Lately it started shuddering at around 50 mph. I had the transmission flushed and asked the mechanic to check the engine over. I thought it could be the transmission, and it needed servicing, but it just doesn't "feel" like the transmission. It feels more like the first few seconds of a car running out of gas. Not a severe shudder but more like it just isn't getting enough fuel or is misfiring. It's VERY intermittent and hard to reproduce.

In short, the mechanic said he was certain it was the transmission. He's a professional but he gave no mention of other potential causes, straight to the most expensive "fix".

So I checked here and found many similar tales with the problem actually being bad plugs or ignition coils. Well, I changed the plugs yesterday (could they make them any harder to reach?) and tested each coil with a multitester. The Chilton book says the resistance across each coil should be 0.55 ohms. Every one tested 0.4 ohms. I fiddled with the tester to try to get more accuracy but each one registered the same. Anyone else have experience testing these things? In the end I just looked for one to be different from the others. I can't imagine they're ALL bad, though I admit it is possible. What sign am I looking for that one is definitely bad? Any other checks I can make as the shudder is still present, though seemingly even more intermittent? Could a bad injector be to blame?

Any suggestions are appreciated before I spend several thousand on a transmission job, if another mecahnic's opinion points to that.

 

How did the plugs look when you pulled them out?
Did the new plugs help the problem any?

 

The plugs looked like 75,000 mile plugs, really. Nothing about them looked out of place. They had a sort of grayish deposit on them but none looked burned or beaten up. Nothing about them looked odd.

I've driven the truck a couple of times since replacing the plugs yesterday. The shudder is still there, but barely noticable. The shifting and idle speeds seem a bit different and it still shakes at idle. Nothing horrible and I keep wondering if it isn't that I am just hyper-sensitive now. I have no trouble at under good acceleration. The shudder has only ever occured wunder moderate throttle at around 50 mph, especially if I have been coasting and put my foot back into gently.

Again, I have a hard time knowing that what I sense is new and out of the ordinary or if I'm just noticing things that have been there but I never paid any attention to.

 

Hmm, shaking at idle? Are the RPMs dropping? I would clean the IAC, its cheap and easy, it can be a pain with the 5.4L engines, but if you devote an hour or two to it, its really not hard at all (just need some basic sockets and such).
Does it still shake if you take it out of drive?

Also try resetting the PCM (remove the neg. battery cable and turn on the headlights, leave it like this for at least 10 minutes. Hook it all back up, start the truck, let it idle with A/C and all components off for 5-10 minutes, then drive like you normally would for at least another 5-10 minutes).

Im still not very inclined to think this is a tranny problem...but I could be wrong. The things I suggested above are all free and easy, so give them a try first.

 

I'm also having a similar problem on my '01 F150 with a 4.6. It started after I "foolishly" decided to clean the engine... of course I thought I took good care of where I pointed the thing, and even taped over some of the connectors. anyhow: I changed the plugs after getting a OBD code reader from the auto parts store. It got better, but now seams to do it around 40 when I step into it moderately from cruising or off throttle.

It's still doing it, but it hasn't set a code since changing the plugs. I'll try this method of checking the resistance. any other suggestions for misfire diagnosis?

Thanks!

 

Just because a coil checks okay statically via resistance doesn't mean that it's good. A coil stress test or power balance test will check for any coils breaking down under load, unfortunately, this requires a scan tool.

 

I had the same problem with mine. I checked out the primary & secondary resitance to each coil. Every one of them checked out. Finally, I had a P0303 and it ended up being the coil after all. Moral of the story is that there could still be a short on the primary voltage side of the coil that you'll probably never find until it throws a code.
As Quintin has stated, I've determined that the easiest way to check the coils is Fords WDS Scantool. It was $83 when I had mine checked out and in the end it turns out to be a lot cheaper
The Scantool checks injector flow and power balance accross the cylinders as well so not only do you find the trouble coil but you find out how your motor is doing at the same time!

 

WHere can I get this scan tool? Dealership? Or is it an aftermarket item? If so, any particular one?

 

The WDS Scantool is at Ford. It's thier "World Wide Data System" Realtime scanner. You have to go to Ford to diagnose your vehicle.

 

Ah, they charge $83 to use their equipment...?

 

They charge you and they do it. You get the results for your $83 trouble shooting purchase

 

Meanwhile your fuel lines get knocked loose, 4 screws are left out of various locations, connectors and cables are left dangling just behind the fan blades...

Oh, gotta get those connectors from Ford

 

I like to keep things simple. A friend had a small shudder at idle after replacing the plugs. I took a very high tech tool, a piece of CVPC ˝” dia. pipe (approximately 2 feet long), and started pushing on each plug’s boot/coil. When I reached the number 8 plug, of course the last one, the shudder went away completely. When I moved the boot/coil in different directions, it changed the operation of the engine. A very sophisticated test. I do not know how he resolved it. I have used the same state-of-the-art leading edge technique on my 4.6L…it worked

Addendum: try pushing on the PVC valves, intake “tube”, IAC, EGR, etc. It may not be the most sophisticated method, but sometimes it works. All you are looking for is a change in the engine speed, sound, shaking, etc.