Tyler Reyes is an experienced automotive technician based in Madera, California, with over five years of hands-on experience diagnosing and repairing a wide range of vehicles. From domestic trucks and SUVs to European and Asian imports, Tyler has built his career working on engines, drivetrains, suspensions, and complex electrical systems. His expertise with modern diagnostic scanners—including digital tools, MDARS, ADAS, and Mitchell ProDemand—gives him dealer-level insight while working in independent shops.... Read more
The Problem
A customer came into the shop with a 2018 Jeep Grand Cherokee with the 3.6L V6 Pentastar engine that was experiencing misfiring issues. The vehicle would run extremely rough, especially at startup, shake while idling at a stop light, and there was a noticeable lack of power when attempting to accelerate or pass another vehicle on the highway. The customer reported that the issue became progressively worse until the vehicle was no longer drivable and would even overheat if driven for an extended time. When the Jeep was brought into our shop, the engine was running rough, with noticeable hesitation, shaking at idle, and misfiring under light loads. The customer asked us to run a diagnostic to determine the cause of the problem, as they could no longer drive the vehicle in this condition.
Diagnosis
A full system diagnostic scanner like YOUCANIC UCAN-II was used to perform a complete system scan, allowing us to verify the presence of fault codes and monitor live data during testing. Additionally, we retrieved information from the factory repair information and wiring diagrams on platforms and databases of ProDemand and Mitchell, primarily to confirm specifications, verify timing alignment procedures, and ensure that all diagnostic steps were carried out in accordance with OEM guidelines. The advanced scan tool and the technical service database are essential for accurately checking the timing and conducting a diagnosis in cases like this. I confirmed that the timing system components had failed, which led to the misfire and drivability issues reported by the customer.
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After reviewing live data and performing further inspection, including a compression test, I was confident that the engine timing had shifted. Testing revealed the timing chain had jumped teeth, which caused the camshaft and crankshaft to become misaligned. I was confident that the misalignment directly led to the customer’s misfire concern and severe rough running condition, as those are common symptoms of P0017.
During inspection, both intake cam phasers (Variable Valve Timing actuators) were also found to be faulty, further contributing to the timing deviation, poor performance, and overall drivability issues. It also makes sense to replace those components if you have a high-mileage Grand Cherokee and you are opening the engine to do timing chain work.
Fixing the Issue
I proceeded with the repair by replacing the timing chain, variable valve timing actuator, both intake cam followers, and oil control valves
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