Diagnosing Ford Engine Problemsby Don Bowman
Introduction and Bottom-End Noises:
Diagnosing a Ford engine problem starts with symptoms. Noises in the engine are the first clue to internal problems. Hard knocking sounds when the engine is started and continue while running, coupled with low oil pressure indicate bad main bearings. This requires replacing the crankshaft and all the bearings. A knocking noise that has more of a tinny sound and increases in intensity with acceleration and goes away when the gas pedal is released and the engine decelerates is very likely a rod bearing or a wrist pin. This requires engine rebuilding. A continuous tapping noise easily recognized in the valve cover area or top of the motor means that the valve train needs adjustment or one or more of the lifters are collapsed. This repair would require replacing the lifters and readjusting the valves.
A rubbing or clanking noise in the front of the motor near or at the water pump indicates that the timing chain is worn out and needs to be replaced. An uneven noise like a wobbling knocking could be the water pump. When the engine is off, grab the fan and move it back and forth to see if the shaft on the water pump moves. If it does, replace it. If a louder than usual exhaust noise is heard accompanied by a distinct exhaust smell under the hood, there is an exhaust manifold leak. Check the manifold for cracks and run your hand around it with the engine running without touching it to try to feel for the problem area. Replace the manifold gaskets. If there happens to be a hissing noise on the top of the engine there is probably a vacuum leak. Check all the hoses for cracks, loose hoses or hoses that fell off the intake manifold. A good way to check the hoses for cracks is to use pliers to pinch off all the hoses at the source one at a time and listen for the noise to subside. Check the intake manifold and throttle body by spraying a small amount of carburetor cleaner on them. If the engine runs better or the noise is gone after spraying, then the problem is a leak on the intake manifold or throttle body. Remember that carburetor cleaner is flammable so do not spray it on the exhaust.
Cam and Ignition Problems:
If the engine will not run and the check engine light is not on, but the engine will crank over check the following: If this Ford has an overhead cam engine, make sure it's turned off and take the top of the timing belt cover off or look into the valve cover to see if the cam is visible. Have a helper tap the ignition key in the start position and see if the cam moves. If nothing happens, the timing belt has failed. If the cam turns or it is not an overhead cam check the ignition. Pull a spark plug wire and insert another spark plug into the end of the wire and lay it on the engine where it touches metal. This makes a good ground. Do not take the plug out of the engine and do this. Have someone turn the engine over and look for a spark. If there is no spark, check another plug. If there is no spark at a second plug wire, check for power at the coil. Check the negative terminal of the coil next with a circuit tester and have the helper turn the engine over. The light should flash. If it doesn't flash, but there is power at the coil, check the distributor cap and rotor. If it is a coil-on-plug design and there is no spark, it is likely the crank sensor is bad. The engine may run, but poorly and might be missing (if it's missing, the idle will be rough). Feel the exhaust and if it is not steady and puffing there is definitely a miss. Spray the spark plug wires with water and look for arcing at the wires. If you can see an arcing spark, replace the wires. If not, use insulated pliers to pull one wire at a time off of the distributor. Each time a wire is pulled the engine should run rough and slow down. A good spark also should be visible when the wire is close to the distributor. If one or more cylinders make little difference when the wire is pulled, mark these cylinders since they are the source of the problem. With coil-on-plug systems simply disconnect each coil one at a time and plug them back in and go to the next for the same result. Disconnect the distributor or all the coil-on-plug coils and do a compression test on all cylinders. Make sure the engine is good before proceeding further. All cylinders should be more than 100 psi and very close--within 5 percent of each other. If any cylinders are low, it is time to check for internal damage. Pull the valve covers and rotate the engine so the valves are closed on the cylinders in question. Use the hose end of the compression tester and hook up the air line to it. Pump air into the cylinder and listen for where the air is escaping. If it is coming from the carburetor or throttle body, an intake valve is bad. If the noise is coming up through the cylinder head with the valve covers removed, it is passing the rings and the engine is worn out. If the air can be heard only escaping at the exhaust, an exhaust valve is bad or cracked. Bad valves require a valve job while piston rings require a rebuild. If the check engine light is on hook up an OBD code scanner and turn the key to run with the engine off and read the code. Cross reference the code number to the explanation that came with the code scanner. Repair as necessary.
Don Bowman has been writing for various websites and several online magazines since 2008. He has owned an auto service facility since 1982 and has over 45 years of technical experience as a master ASE tech. Bowman has a business degree from Pennsylvania State University and was an officer in the U.S. Army (aircraft maintenance officer, pilot, six Air Medal awards, two tours Vietnam).