F150Torqued

@FordBoy05 - I agree with all the prior advice you've been getting - and believe you need a good CLEAN plug job with proper plugs and new boots. Not sure THAT is the source of the symptom in the thread title though. But if you have access to an IDS system there are lots of things available from the OBDII system that you can check. Fuel Rail Pressure, Fuel Pump Duty Cycle %, and on and on that might effect stability of idle / acceleration etc etc.

I don't want to throw a 'monkey wrench' into the mix - but because of your thread title I might do some looking toward the 'fly by wire system'. Engine idle rpm is digitally maintained by the PCM. It is really quick and there is no reason it should vary from desired RPM more than a very few RPMs. There are a bunch of different throttle position readings (TP - throttle position %, TPREL - relative throttle position % - TPCMD - Commanded throttle position %, TP1 - Throttle position1 volts, TP2 - Throttle positon2 volts, TPD - Throttle position desired Deg,), and an equal number of Accelerator Pedal Position PIDs.


It is a complex system that does lots of self checking and can impose throttle limiting and limp mode pretty readily. But it sounds like that system may be seeing unstable sensing readings or having sticky difficulties maintaining a constant RPM.


Might be as simple as cleaning throttle body.

digitaltrucker

Does this year model have an IAC?

F150Torqued

No sir. To my knowledge the 2005 5.4l does not. It just 'twittles' with fuel trims and throttle plate to get there.

FordBoy05

Ok so this morning, the truck has a slight shaking idle about as normal as what it usually has but then I gave it a quick burst of gas and then came to a stop, and it idled a lot smoother. You could defiantly tell a difference. No shaking just a smooth idle. Also when I turned the truck off, it shut off smoothly and it didn't shake the truck when it turned off. I'll be taking the IDS home today so I can plug it in and drive around to see if I can see if there are any misfires that aren't being shown up.

digitaltrucker

Bad gas?

FordBoy05

Don't think so because I usually get it from pilot and I've gotten it from other stations and it still had a rough idle. Forgot to mention about a few months ago, I was driving on the highway and it made a one single buck on the highway. When I got off the highway, the rpms went below 500 and stayed there for some time and it was doing the same thing, constant vibration idle, fluctuation, breaking up on acceleration. Eventually fixed itself. Then the very next day I was driving and I let off the gas and the CEL flashed about 3 of 4 times. Weird thing is is that it didn't feel like a mis but the light was flashing. The truck also seems to tick a little louder when this vibration and spidering happens.

FordBoy05

Think I have found the problem to be vct solenoids. The truck acted up again while I was driving and right after it shifted i could feel a buck. Then once again, same problem as before it had a shake at idle and a uneven accel. This time it had a very faint knock that you could hear while it was idling and shaking. When I stepped on the gas there was this clack noise. As I'm typing this though, I feel like it could also be a misfire. Also it had just rained this morning so maybe that has something to do with it? I brake torqued the motor and there was no horrible shake so that's why I was thinking vct solenoids.

FordBoy05

This morning the CEL was flashing for a good 3 minutes this morning. The only coils I have left to replace is 1,2, and 8. All other are replaced with motorcraft coils. Thinking its most likely the coils like everyone has suggested.

BadFish523

Coils rarely go bad. Most of the time replacing coils is a waste of money. Replace the boots and springs on the old coils first. This will usually take care of a misfire. My misfires were fixed with new boots and springs.

F150Torqued

https://www.f150forum.com/f4/5-4-rou...3/#post5311244