How the VCT Solenoid Works:
The VCT or Variable Cam Timing solenoid is a device used in modern engines to change camshaft position timing in relevance to engine speed and engine timing allowing the engine to produce more horsepower without adding excessive overlap to the camshaft design.
The way the VCT Solenoid works is as follows:
The VCT solenoid works with oil pressure, it receives a signal from the ECM when the camshaft needs to be rotated either in the advanced mode or retarded mode depending on engine load and speed.The VCT solenoid is able to accomplish that by altering the oil flow in the passages that lead to the cam phaser(s), there are passages to advance the valve timing ( open the valves earlier), and passages that direct the oil to retard the valve timing ( open them later)
The purpose of the VCT or Variable Cam Timing system is to allow the engine to move larger volumes of air in and out of the cylinders to generate maximum horsepower.
Vehicles with DOHC ( Dual Overhead Cam ) engines usually have two VCT solenoids mounted in each cylinder head, one for each camshaft, allowing the Engine Control Computer to activate each VCT timing mechanism in each Camshaft separately.
NOTE: The Cam phaser is mounted on the front of the camshaft(s) it is driven by the engine's timing chain or timing belt depending on the engine's design.
During our test drive we noticed a very slight improvement in the truck's response, but it was obvious that the problem was still there, we scanned the truck again with a Snap-on Solus scanner, and we found the same engine trouble codes (P0340, P0012, P0345).
We decided to replace both VCT solenoids for two reasons:
1) The Scanner showed code P0012 as bank 2, the book showed it as bank 1.
2) We didn't want to be cheap, replacing only one solenoid and a month later the second VCT solenoid would go out.
Here are the steps needed to replace the driver's side (Bank 2) VCT solenoid, please note that replacing the passenger side is a lot easier because there is nothing on the way, and basically the same steps apply to replace the VCT solenoid in bank 1
Remove the bolt that holds the air intake tube in place and remove it from the truck
Remove the nut that holds the power steering bracket attached to the cylinder head
Loosen the bolt at the bottom of the power steering bracket, this bolts holds the bracket against the engine block.
Note: It is not necessary to remove the bolt, just loosen it enough and the bracket will slide out.
Remove the three bolts that secure the power steering reservoir, move it out of the way, next proceed to remove the power steering reservoir bracket out of the truck.
Note: It is not necessary to empty or remove the reservoir, just lean it against the fender in the upright position.
Unplug the electrical connector from the VCT solenoid by pressing the tab and pulling it up
Carefully pry the VCT seal from the valve cover
With a long torx screw driver, loosen the bolt that holds the VCT solenoid in place, at the same time, with the other hand pull gently on the Solenoid, that way it will come up as you loosen the bolt, remember to keep pressure on the torx driver against the bolt, that way you eliminate the chance of the bolt falling inside the engine
Install the bolt on the new VCT solenoid
Proceed to install the new Solenoid maintaining pressure on the bolt, slide the VCT solenoid gently in its place and tighten the bolt.
Don't forget to add a thin coat of oil to the part of the VCT solenoid that goes inside the engine.
Clean the cavity in the valve cover where the VCT seal goes, lubricate the inner part of the VCT seal to avoid tearing it as you install it in its place, use a socket long enough to avoid damaging the VCT solenoid as you install the seal
Install the parts you removed in the reverse order you took them off and you are done.
As mentioned earlier: The passenger side or Bank one VCT solenoid is easier to replace because there is nothing obstructing its access, so there is no need for us to illustrate the other side.
The pictures and instructions are for a 2004 Ford F-150 with a 5.4 Liter Triton V-8 Engine, but as you know, it applies to all the Ford Vehicles, cars or trucks equipped with a 5.4 L. Triton V-8 engine.
After we finished installing both of the VCT solenoids in the truck, we took it for a test drive, WHAT A DIFFERENCE!!, It came alive, it has plenty of power throughout the RPM power band, no backfiring and very responsive.
We scanned it again just to make sure, and we found no trouble codes.
We hope that you find this information helpful, and in the event that you decide to replace the VCT solenoid in your car or truck yourself, you will have a detailed step by step guide on how to do it.