Some 2006-08 4.0-liter Ford Explorers and Mercury Mountaineers, as well as 2007-08 Ford Explorer Sport Tracs, may produce a buzz or hum from behind the center or right side of the dash while idling in gear or driving under light loads in the 1100-1400 rpm range.
One likely cause for the noise, Ford reported, is the powertrain control module (PCM) vibrating against its mounting bracket. Insulating the module from the bracket with some urethane foam tape, part #164-R4902, should eliminate the irritation.
Start the fix by removing the module from its mounting bracket. Now grab a pair of scissors and cut a 1-3/16” x 2-3/8” piece of foam tape from the supplied roll.
Using the illustration above as a guide, stick the tape to the center of the rectangular opening on the bracket, making sure it wraps over the lip and adheres to the inside and outside edges, as shown.
Reinstall the powertrain control module, making sure you don't pinch the vacuum line from the heater case. To complete the repair, apply the brakes, start the engine, put the transmission in gear, rev the engine to 1400 rpm and verify that the buzzing or humming noise has been eliminated.
Drivers of 1999-2001 GM vehicles with 2.2-liter four cylinder engines may come into your store with a complaint of a droning-type sound on cold starts.
GM said the noise occurs most frequently on vehicles with manual transmissions and is likely caused by resonance setting up in the drive belt span between the air conditioning compressor and alternator.
Installing a revised drive belt, part #12575450, should eliminate the irritation immediately.
Some 2006-07 Sedona minivans built on or before Feb. 5, 2007, may emit a knocking sound every time the a/c compressor engages.
Kia attributed the noise to a poorly designed compressor clutch hub assembly. Installing an updated part with improved dampening characteristics, part #97644 4D900FFF, should eliminate the condition.
Some 2004-06 Lancer models with 2.0-liter engines may turn on the Check Engine light and store trouble code P0171 in computer memory.
One likely cause, Mitsubishi reported, is a vacuum leak between the fuel injector insulators and the base of the intake manifold ports.
Installing four new-design insulators, part #MD087060, and injector O-rings, part #1465A188, should seal off the leak and eradicate the code immediately.
Note: After the injectors are reinstalled, ensure that the top portion of the insulators are flush with the injectors and the bottom portion flush with the intake manifold ports. If you notice gaps, press down firmly on the fuel rail until the gaps are eliminated.
Some 2005 Dodge Ram Trucks with 5.7-liter engines built on or before June 5, 2005, may turn on the Check Engine light and store trouble codes P0420 and/or P0430 in PCM memory.
If there are no symptoms or other codes stored, Chrysler says the trouble is most likely due to lazy oxygen sensors.
Updated sensors are now available to eliminate the concern. Order part #56029049AA for 1500-series trucks, or part #56029050AA for 2500- and 3500-series pickups.
After the new sensors are installed, you'll have to have the PCM flashed with updated software files. Check with a Dodge dealer for the specific calibrations.
“Factory Fixes” is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected]