Ford introduced the modular engine (4.6 liter) in the 1991 Lincoln Town Car. A multitude have been produced since, in a 2, 3 and 4 valve per cylinder arrangement and in various displacements. They are popular as 4.6 liter and 5.4 liter, in Ford and Lincoln cars, SUV vehicles and trucks.
The Ford Modular engine is well designed, but very "picky" as to the lubrication and oil filter
Originally 5W30 motor oil was specified but later Ford changed to 5W20 and 5W20 synthetic blend. The oil filter also has a specific anti-drain back valve and for good reason.
We are seeing a good many of Ford modular engines with a costly problem. The timing chains are relatively long. They are supported by plastic guides and kept tight by hydraulic tensioners. With the proper lubrication and oil filter this works very well for a great many miles. Problems begin when improper viscosity oil and substandard oil filters are used.
With a substandard oil filter the engine oil may drain back to the oil pan when the engine is turned off. A lack of oil pressure means tensioners cannot immediately tighten the timing chains on startup. When this occurs slack in the chain tends to jerk and the plastic timing chain guides can break.
Symptoms of a broken timing chain guide can range from noise on startup (not always) to rough idle to a check engine light. This engine was fitted with the proper Motorcraft filter after the noise started. Unfortunately it was too late to prevent an expensive repair.
A broken chain guide is apparent, once removed and compared with a new part. The guide most often breaks where the mounting bushing passes through. This allows the chain to drop down and often it starts to rattle, until the tensioner tightens it.
When the timing chain guide (1) breaks, the chain drops down. The chain tensioner (2) attempts to take up the excess slack in the timing chain. When the tensioner piston extends, the chain is pulled tight. Removing this slack on one side of the chain also causes the cam sprocket (3) to rotate and change camshaft timing on that bank.
Rotating one cam sprocket disturbs valve timing relative to the other side of the engine. This can cause a rough idle can set diagnostic trouble code (DTC) P0300 and codes for lean and rich operation. Many times these engines come to us, after having been mis-diagnosed elsewhere. Needless part replacement has often been a further waste of money. Repair involves timing cover removal and replacement of the chains, guides, tensioners, etc. Changing to the proper oil viscosity and a Motorcraft oil filter, prevents an expensive repeat of the problem.
Timing chain problems can be greatly decreased by a few simple steps