LeSabre's Rough Idle Points to Worn Engine Mounts

Having worked on a 2008 Buick Lucerne with the same 3.8L engine last month, the symptoms you describe match my experience with failed motor mounts. The harsh vibrations during idle were a clear sign of mount failure in my case. The diagnosis revealed two defective engine mounts that allowed excessive movement, particularly noticeable at idle. The front mount was completely separated from its bracket, causing the engine to shift more than normal. This shifting created connection issues with several sensors, triggering multiple error codes. Mount failure on these engines is fairly common after 150k miles. The rubber deteriorates over time, especially if exposed to oil leaks. A proper inspection should include checking all mounts while the engine is both running and off to observe movement patterns. The repair was serious enough that driving with failed mounts risked damaging other components, including transmission lines and electrical connections. In my case, the excessive engine movement had already started affecting the throttle position sensor wiring. A thorough diagnosis should include a visual inspection of all motor mounts while someone revs the engine slightly. Excessive movement or cracked rubber are clear indicators of mount failure that need immediate attention.

Thanks for sharing your experience. I faced nearly identical vibration issues with my 2006 LeSabre last year. After replacing both the motor mount and transmission mount, the harsh vibrations completely stopped. The mounting bracket on the passenger side was also damaged and needed replacement. Did the repair cost end up being reasonable in your case? My total came to around 600 Euro for parts and labor, but prices vary. Also curious if you noticed any other problems pop up after fixing the mounts? In my case, everything has been running smoothly since the repair.

After completing the engine mount repair, the total cost was surprisingly reasonable at 95€ for fixing a faulty cable connection that was causing sensor issues. The defective engine mount turned out to be the root cause, and once replaced, all error codes cleared up. The transmission mount and mounting bracket were inspected and found to be in good condition, so no additional replacements were needed in my case. The initial diagnosis was spot-on, the excessive movement from the bad mount had damaged some wiring connections, but nothing major. Since the repair six months ago, the car has been running perfectly with no vibration issues or new problems. The idle is smooth now, and all sensor readings are normal. This really shows how one defective engine mount can cause a cascade of symptoms that might seem unrelated at first. The most important takeaway was catching the mount failure early before it could cause more extensive damage to other components. Regular inspection of engine mounts during maintenance can help spot these issues before they become major problems.

The outcome was surprisingly similar to yours. I took my car to a well-known mechanic who diagnosed the issue right away. The motor mount and transmission mount needed replacement. A broken mounting bracket on the driver side also required attention. The total repair came to €580 including parts and labor. The shop completed all repairs in one day. Since fixing the mounts, the car runs perfectly smooth with no vibration at idle. All error codes cleared up and never returned. The rough idle completely disappeared after addressing the defective engine mounts. My mechanic explained that catching mount failure early prevented additional damage to sensors and wiring. The repair costs were reasonable considering the potential for more expensive problems if left unfixed. Six months later, everything still works great with no new issues. This experience taught me not to ignore unusual vibrations, as they often point to mounting problems that should be addressed promptly. Regular inspections of engine mounts during maintenance could help catch these issues early.