Problem Solved: Dodge and Chrysler Pentastar V6 Misfire
The Problem
The Stellantis Pentastar 3.2L and 3.6L V6 have a wide application across the Jeep, Ram, Dodge, and Chrysler product line. Although a solid design, engine misfires are a common problem with this platform. In this “Problem Solved” an owner experiencing this problem with a 2015 Chrysler Town & Country relied on a local shop to identify and repair the engine misfire issue. The shop replaced many components, including a crankshaft sensor, camshaft sensors, ignition coils and spark plugs. In addition, one cylinder head was removed and sent to a machine shop for service. When the customer picked up the vehicle, the misfire persisted. Haakan Light, USA Training and Development Manager for TOPDON, tackled the issue using TOPDON tools.
The Tools
- TOPDON Phoenix Smart
- TOPDON Phoenix Oscilloscope
- Pressure transducer, 600A Amp clamp, and ignition COP probe
The Solution
A pre-scan confirmed a cylinder 1 misfire. Using the TOPDON tools to access the OBDII data stream, Light viewed the misfire counts, which were significant, and then viewed the OEM data stream for clues. This indicated that the injector pulse width in cylinder 1 was off, so he did a relative compression test, which confirmed lower compression in a cylinder. He followed this with a capture of an intake vacuum pulse using the pressure transducer, which revealed a lesser amount of vacuum in the intake manifold. The data pointed to a valvetrain problem, and further testing implied the intermittent loss of compression in cylinder 1 was a mechanical issue.
The original mechanics who worked on the vehicle did not localize the origin of the misfire, and the machine shop failed to advise the repair shop to replace rocker arms, known problem components on this engine. This resulted in parts being replaced unnecessarily.
When replacing rocker arms on this engine, it is advisable to replace all rocker arms, valve springs and lifters, and it’s important to inspect for camshaft damage. On this vehicle, no damage was found to the camshaft or lobes. No major damage was evident on the valve rocker arms, however the small bearing “wheels” had flat spots and were no longer round, intermittently causing the valves to not open completely. Replacing the valve rocker arms was the acceptable repair.
The Video
Haakan Light walks you through the process of how this problem was solved on TOPDON’s YouTube channel. The video details the process for reading the settings on the oscilloscope, examining the waveforms, and shows the diagnostic steps taken on the scan tool’s screen. With the right TOPDON tools, any shop can solve troublesome repair issues and earn satisfied customers.