Hi. I have 2002 5.4L f150 120k miles. Bought it almost 2 years ago and did not notice this vibration at the time but it could have been there and I didn't realize it. The trans was replaced by ford with a reman at 90k. I'd assume they inspected the trans mounts but who knows.

At idle only, there is a vibration. Enough that I can see water in a bottle moving and a plastic bag shake., felt through the seat, hand on engine can feel it, can feel it through the door..etc. Very annoying. At 700-750 rpm it goes away. Happens in all gears.

I don't want to shotgun approach this. What I've done:

Replaced plugs and coils since it needed them anyway. They looked good! No difference.
I've sprayed the maf down and cleaned the throttle plate (I know your not supposed to but some 16 year old will try to tell me it cured his idle and he gained 10 mpg, so I figured I would mention it).
I've removed the IAC and cleaned it, plunger moves freely. My idle does not fluctuate.
I have watched mode $6, it's not a misfire.
I have removed the pcv hose and checked for cracks - it's in good shape.
Replaced the pcv since it's cheap.
Ran Chevron tehcron through it.
Checked codes - nothing. I have an edge and it happens on all tunes as well as stock.

I have ability to read live data but do not know enough to interpret it, so that is about useless unless you can provide me acceptible ranges.

Suggestions? @Bluegrass 7?

 

First clear up the reference to 700-750 rpm because that is the normal design idle rpm range.
Is the motor idling lower than this range?
If yes that is a problem to solve first.
Otherwise do a compression test to see if one cylinder is on the low end of the average..
If this would be the case, at idle it would show up as a roughness at such a low rpm.
Good luck.

 

I double checked the engine idle RPM once up to operating temperature and found it averages between 620 to 640 in Park and Drive with the AC/Heat off, according to the Edge.

 

When it idles in Park or Neutral does it do it? Catalytic Converter shields all still tight? Most of mine are gone or I tore off the remains on my 98. All the salt up here really eats at them. They can really make a racket and vibrate when they are loose. Does it run rough, or just vibrate?

 

Yes it does it in park, neutral and drive.

Catalytic converter shields would not create a vibration like this...think about it. They are stationary. They may vibrate as a result of this issue but would certainly not be the cause.

I do know the sound that you are referencing by them contacting other metal but that is not my issue and not relevant in this situation.

I would not consider it "running rough". Only noticeable constant vibration at idle. All other drivability functions are seemingly normal.

 

I don't know if your Tach reading is correct or the motor is idling to low. The program is set to keep idle at close to 750 +/- 50 by design.
The PCM program uses the crank sensor to determine the actual RPM and applies any 'corrections' to the IAC air bypass opening keeping the RPM within the table value by doing a compare function within the program..
At lower rpm the transmission is loading the motor even lower and may show up any cylinder that is down on power.
For example waiting at a stop sign or light on an up grade allowing the trans to keep the truck from moving will show up a skip if one is present.
There are a number of reason to keep the idle at 750.
To compensate for varying loads from sources like power steering operation, A/C on/off loads, alternator output from falling below voltage levels, to recover Idle on deceleration so there is no tendency to stall.
A way to see what you really have is to fully warm the motor then at idle remove the IAC connector and see what the idle falls to.
It should fall into the 500 rpm range but be reasonably smooth on a fault free motor.
When IAC is plugged up again the idle should return to the 750 range.
Good luck.

 

LOL...Yeah...they are stationary until they are half rotted off and vibrating on the floor pan. Just thought I would throw it out there, I have no idea how severe or minor the vibration is. Good luck.

 

No biggie. I'll see if I can get a video that actually depicts whats happening.

 

An update - I have not had a chance to check the IAC. Tomorrow or Sat I will.

I used the odometer trick to show the engine RPM and at Idle in all gears it does not go above 650 for more than a split second.

On an unrelated note, I've been watching the temperature as well since I had the odometer in test mode. I have not had a reading of higher than 188 deg F or 87 deg C. Even when the outside temp is 40 F. Might be time for a new T-Stat. Hopefully I can gain some MPG as I've been getting high 9's to 11 all winter.