Hi guys. I've helped repair a few of these, and it is indeed a better choice to replace the engine than try to repair it. (Professionally-rebuilt, or "crate" engine; not a used one from a salvage yard). The timing chain setup is a nightmare. Holding the camshafts in position while the variable valve timing components are installed is tricky, and even using Ford's special tools won't ensure the chains will go on right. The front cover is massive and requires a lot of front end components to be removed, then, the parts are very expensive.
These engines don't use hydraulic lifters like those that have worked fine since the 1960s. Instead, they use selective caps over the valve springs, similar to what many motorcycle engines used in the 1960s. The problem is, when there's an annoying valve tick, you have to disassemble the valve train again to figure out which one is noisy, then lift that camshaft to remove the cup and calculate the thickness of the needed replacement. Lifting the camshaft means taking the front cover off again along with the timing chains. That's a good day's job for two people each time it has to be done over. No one will buy a used vehicle with noisy valve clatter, so you're stuck driving it that way if you don't want to go through the time and expense of tearing it apart a second or third time.
These are very small engines that are run near maximum power all the time, so 130,000 miles is a pretty good achievement. The size is appropriate for a minivan. They're used in Expeditions too. They get the job done, but there's little power left over for pulling a trailer.
Jumped timing chains are common on some engines, including the 3.5L, but rather than guessing based on historic failure rates, the diagnostic fault codes you listed are what points to this. I don't think over-filling the oil by a couple of quarts would cause this, but I'm happy to listen to other opinions. Failing oxygen sensors won't cause a rough-running engine. A jumped timing chain will. Excessive oil level can allow it to be hit by the spinning crankshaft. That can whip air into that oil. I don't think two quarts is enough to do that. We used to race street cars at the local circle racetrack, and it was customary to over-fill the oil to prevent cavitation on hard high-speed corners. We never drained that extra oil out later. What's more harmful to the variable valve timing components is low and / or dirty oil. Pressurized oil is used to make the adjustments to valve timing as you drive. The small orifices used for switching and adjusting the amount of timing advance don't like dirt particles that can be small enough to make it through the filter. To my knowledge, a plugged solenoid doesn't result in component damage, but it will result in a major reduction in the power you're used to at highway speeds.
Friday, October 10th, 2025 AT 11:39 AM
