This topic is probably not new, but it was to me and I'll share my experience.
My 95 4.6L had a check engine light on so I went to a local (central Texas) Goodyear service center (Lamb's Tire) and had the problem diagnosed ($89). They found that the Mass Air Flow (MAF) sensor was "dirty" and needed replacement. He said they would need to get the part from a Ford dealer and that the job would cost $483. I specifically asked the mechanic and the service writer if the sensor could be cleaned. They both said no. I declined the service and went directly home and onto the net.
I found in fact that fouling of the MAF is very common on 4.6L Ford applications. I also found that the MAF is easily cleaned or replaced with a refurb for $90-100. The hardest part of the job is finding a #20 security type Torx bit (the tamper resist type). I found a 6 pc set at Sears for $10 (pn 925702). You'll also need a can of CRC brand QD Electronic Cleaner (pn 05101 about $3 at most auto stores) and a open end wrench to remove the battery cables (5/16").
The procedure is simple. Disconnect, in this order, the negative and positive battery cable. Find the MAF. It is the chip like device located just downstream of the air filter box on top of the air duct. Its dimensions are about 1.5 x 3 X 1/4" and it has a wire harness attached. Remove the 2 #20 security type TORX screws. Lift the device straight up and off its mount. Don't lose the (~5/8") O ring that seals the unit.
The working part of the MAF is revealed as 2 tiny wires that normally are presented into the air flow in the duct. These are resistors that measure the air flow in the duct by comparing the current flow through the resistors. The current changes when air flow cools the resistor. When they become coated with grease or dirt they become insulated to the cooling affect of the air flow and thus give falsely low readings. This will result in a lean air to fuel mixture.
Handle the device carefully, avoid touching the wires. Spray the wires with a couple burst from the cleaner. You will notice a big difference; the wires will become silvery clean. Let the wires dry a few seconds and remount the device. Reattach the battery, positive cable first. The removal of the battery will have reset all electronic devices, including the emission control computer.
Start the car. The check engine light will now be out. All of the engine control parameters will reset themselves during the next 20 or so miles of driving. If you need to get the engine smogged right away, first drive the car for the 20 miles varying the throttle from full to city type driving. This will likely reset all engine parameters to ready.
Can of cleaner, $3
Screw driver bit, $10
Avoiding a $500 rip-off, priceless.
My 95 4.6L had a check engine light on so I went to a local (central Texas) Goodyear service center (Lamb's Tire) and had the problem diagnosed ($89). They found that the Mass Air Flow (MAF) sensor was "dirty" and needed replacement. He said they would need to get the part from a Ford dealer and that the job would cost $483. I specifically asked the mechanic and the service writer if the sensor could be cleaned. They both said no. I declined the service and went directly home and onto the net.
I found in fact that fouling of the MAF is very common on 4.6L Ford applications. I also found that the MAF is easily cleaned or replaced with a refurb for $90-100. The hardest part of the job is finding a #20 security type Torx bit (the tamper resist type). I found a 6 pc set at Sears for $10 (pn 925702). You'll also need a can of CRC brand QD Electronic Cleaner (pn 05101 about $3 at most auto stores) and a open end wrench to remove the battery cables (5/16").
The procedure is simple. Disconnect, in this order, the negative and positive battery cable. Find the MAF. It is the chip like device located just downstream of the air filter box on top of the air duct. Its dimensions are about 1.5 x 3 X 1/4" and it has a wire harness attached. Remove the 2 #20 security type TORX screws. Lift the device straight up and off its mount. Don't lose the (~5/8") O ring that seals the unit.
The working part of the MAF is revealed as 2 tiny wires that normally are presented into the air flow in the duct. These are resistors that measure the air flow in the duct by comparing the current flow through the resistors. The current changes when air flow cools the resistor. When they become coated with grease or dirt they become insulated to the cooling affect of the air flow and thus give falsely low readings. This will result in a lean air to fuel mixture.
Handle the device carefully, avoid touching the wires. Spray the wires with a couple burst from the cleaner. You will notice a big difference; the wires will become silvery clean. Let the wires dry a few seconds and remount the device. Reattach the battery, positive cable first. The removal of the battery will have reset all electronic devices, including the emission control computer.
Start the car. The check engine light will now be out. All of the engine control parameters will reset themselves during the next 20 or so miles of driving. If you need to get the engine smogged right away, first drive the car for the 20 miles varying the throttle from full to city type driving. This will likely reset all engine parameters to ready.
Can of cleaner, $3
Screw driver bit, $10
Avoiding a $500 rip-off, priceless.