This vibration is driving me nuts .
I start the truck, engine runs good , engine idle , press the gas , at around 1200-1500 RPM the truck starts vibrating , I mean bad shake, passing 1500 rpm we're back to the business and everything is fine. it's the same while driving the truck. low speed caused severe shake . I went through previous posts and did not find any solution. please advise.


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F150 2001 v6 4.2L 200k miles

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check the u joints...I had the issue on my f250 and I crawled underneath and my u joint was AFU

 

harmonic balancer

 

please be more specific guys. I'm new in this world.
Thanks

 

where your driveline connect to the transfer case and the rear diff there is this cross looking thingy that lets the driveline move and still spin....its called a u joint

Harmonic Balacer is the big pulley in the front of the engine

 

but do these affect even when the truck is in park position ? It shakes even in neutral or in park .
thanks

 

The harmonic balancer would. The harmonic balancer is behind the big pulley on the front of the engine.

 

hey,
I do have some errors too which might be the cause: "MISFIRE ON CYL 1 , 4" and the fuel lean in bank 1 and 2.
So I went ahead and changed the spark plugs and measured the coil pack which is fine. I dont know if misfire causes that vibration or not, but I really dont know what else to check , I just measured the resistance on ignition wires , Number 1 is measuring 4k and the rest are 5k ohms. is that ok?

 

Just posted on other thread. Yes, the miss fire can caused the vibration. Have the same engine in my 02 with 170K. In winter time I get PO171 & PO174 banks 1 & 2 lean. Haven't had the vibration concern yet! Am told by the Ford mechs here is Vegas the two codes thrown are intake gaskets. Bought them last week $140.00. Its not intake gaskets like used on all other engines between the aluminum intake manifold and the cylinder heads. Its rubber seals, sealing the big phenolic plenom chamber on top of the intake manifold. Even the bolts attaching the lower half of the chamber have seals and have to be replace with upgraded version. Haven't done the job yet as its HOT here in Vegas and am not throwing codes. Good luck and keep me posted as to your results.