Cleaning the MAF
In order to clean the sensor wires, you must remove the MAF from the car. Once removed, spray some electrical contact cleaner or non-chlorinated brake cleaner (something that leaves NO residue) through the sampling tube over the wires.
The MAF should be clean inside. If not, you have a leak that is letting air in that isn't being filtered. The wires may or may not look slightly off color. They can become oxidized over time, which can affect readings. Excess oil from a K&N or other open element filter that has been over-oiled can foul the wires, as well.
Test to check for VCT problems
Starting in 1998, Ford began using variable camshaft timing (VCT) on the 2.0L DOHC engine used in the Contour/Mystique and Escort cars. The purpose of varying the exhaust camshaft timing on these engines is to help reduce emissions similar to the way an EGR valve would, and also to help increase fuel economy. By retarding the exhaust cam timing, some of the inert exhaust gas is left in the cylinder for the next intake stroke. This in turn cools the combustion chamber, reducing NOx and HC emissions. With the VCT, there is no need for an EGR valve, since retarding the exhaust camshaft timing creates the same effect.
The total amount the exhaust cam can be retarded is 30 degrees (60 degrees of crankshaft revolution). The exhaust camshaft has a reluctor ring on it to trigger the camshaft position sensor. The reluctor ring consists of four equally spaced teeth, with one additional tooth in the middle to designate where the TDC is. Sometimes the reluctor ring is called a 4+1.
When the PCM compares the camshaft position sensor signal to the crankshaft position sensor signal, it can then determine where the camshaft is and if it is moving properly when it commands the VCT solenoid to actuate. The VCT solenoid is supplied with engine oil pressure and uses that internally to create a mechanical force to adjust the position of the exhaust cam gear on the exhaust cam.
The cam gear is spring-loaded in the fully advanced position, so if the VCT solenoid becomes damaged or malfunctions, the car will still maintain normal operation and performance. However, if the cam gear mechanism malfunctions, or if the timing belt is installed incorrectly, the exhaust cam can end up in the fully retarded position, giving you the same effect as having an EGR valve stuck wide open ... rough idle, stalling, hesitation on tip in, etc.
Three codes relate to this system: Code P1380 VCT Solenoid Malfunction, Code P1381 VCT Over-Advanced and Code P1383 VCT Over-Retarded.
Code P1380 is strictly related to the electrical circuit of the solenoid, PCM and wiring. If the PCM tries to energize the VCT solenoid and doesn't see any current flow or too much current flow, Code P1380 will set. The normal resistance of the VCT solenoid is 3 to 6 ohms. That resistance should not change by any noticeable amount even with changes in temperature. If the resistance is OK at the PCM connector for the VCT solenoid (measuring from the vehicle power circuit, pin 71 or 97, to the control pin for the solenoid - usually pin 44 or 45), you can also perform an amp draw test on the circuit. With the PCM disconnected, turn the key on. Using a digital ammeter, place the negative lead of the meter on battery negative, and place the positive lead to the control pin for the VCT solenoid. The amp draw should be in the 2 to 4 amp range. Only leave the solenoid grounded long enough to get a reading, preferably no more than one or two seconds. The PCM normally duty cycles it, so leaving it fully grounded for more than a couple of seconds can cause damage to a solenoid that is still in working order.
Here's another test you can do to make sure it is mechanically working: With engine running, using a jumper wire, back probe the ground side of the VCT solenoid. Then rev the engine up to 2,500 to 3,000 rpm and momentarily ground the VCT solenoid; again, only for one to two seconds. You should hear a noticeable difference in the way the engine runs.
This same test can be performed to help diagnose a Code P1381, which indicates that when the PCM commanded the VCT solenoid to operate and retard the cam timing, it did not see any or enough change. This can be caused by a mechanical problem with the cam gear assembly, a bad VCT solenoid, or a problem with contaminated engine oil. Since the VCT solenoid relies heavily on oil flow to create the force to move the cam gear assembly, anything that causes poor oil flow, such as dirty oil, metal chips or flakes in the oil, can affect how well the VCT solenoid functions.
Code P1383 indicates the cam is too far retarded during its “at-rest” position. The majority of the time when we see this code, it has set because the timing belt was installed incorrectly. Be sure to check the basics ... make sure the cams and crankshaft are in time.
Armed with this information, hopefully the next time one of these cars comes in to your shop you will be able to quickly and efficiently diagnose the problem! Remember, if you need help, we are just a phone call away! By Bob Mordorski.