General Motors
Some 2008-09 Cadillac CTS and CTS-V models may produce a clunk-type noise from the rear while being driven over bumps or rough road surfaces. According to GM, the noise is most prominent in vehicles built from Jan. 14, 2008, through Sept. 1, 2009, and is probably due to contact between the lower half of the rear shock absorber and the suspension knuckle. An unseated or damaged bushing is the likely culprit.
To make a proper diagnosis, put the vehicle on a lift and look for shiny marks at the shock clevis bracket, which indicates contact between the shock and the knuckle. If you see the witness marks or the bushing appears loose or damaged, that's your cue that the bushing needs to be replaced. Unfortunately, Cadillac doesn't furnish the bushing a la carte, so you'll have to replace the entire suspension knuckle with an upgraded design to remedy the problem. Check with a dealer for the part number of the new knuckle.
Chrysler
Drivers of 2007-08 Dodge Nitro models with 4.0-liter engines built before Jan. 17, 2008, may come into your store with a complaint that their engine idles roughly or drops its idle excessively after putting the transmission in drive following a cold start. If there are no trouble codes present when the idle complaint occurs, you're most likely dealing with software anomalies in the PCM, Chrysler said. Reprogramming the module with updated software is the only surefire remedy. Check with a dealer for the specifics of the flash.
Ford
Some 2005-08 Mustangs with 4.6-liter engines and manual transmissions built before Dec. 13, 2007, may produce a rattle or buzzing noise from the engine compartment for several minutes following a cold start.
Ford says the noise typically occurs in the 2000-2500 rpm range, usually goes away once the engine warms, and is most likely due to the separator plate between the engine block and transmission vibrating or making contact with the flywheel. Installing a revised separator plate, part No. 8R3Z-7007-A, should eliminate the condition.
"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]