SUV shakes at low RPM's

These trucks are real bad about leaking coolant from failed intake intakes (plastic ones) and intake gaskets. The coolant will travel down the edge of the intake and seap into the plug holes and contaminate the coil boots, ruin coils, and spark plugs. Your vehicle probably did have. Bad plug, but what was the root cause? If there are no signs of coolant contamination, it could be the coil. That is if it has an ignition misfire anyways. There are several other things that can cause a misfire, I’m just giving a most common scenario for what repair has already been performed.

Hello my name is Dave.

First question I have is if you know which cylinder is misfiring? If it is the same one as before the easiest way to determine if it's a faulty coil ( there are no plug wires on a 5.4) causing the plug to foul is to switch it with another coil location and seeing if the problem follows the coil, if it begins to misfire on the new cylinder where the suspected bad coil is that tells you know if that is the most likely cause of the issue. If you need further assistance it would be of great help if you could take a picture of the tip of the spark plug from the cylinder that is misfiring. I hope this has been helpful and thank you for using 2CarPros