Problem: The customer’s concern was that engine would not idle after it had warmed up. The malfunction indication light was OFF. If the engine speed was held over 800-850 rpm, the engine would stay running.
The tech replaced the throttle body, performed the throttle body relearn procedure and replaced the negative battery sensor. After those repairs, the problem still existed. Next, he checked all grounds for continuity and the throttle position sensor (TPS). The grounds were good and the TPS test results were within specifications so he decided to check intake and exhaust cam phaser operation with a scan tool.
He immediately noticed that the exhaust cam phaser advance dropped to zero right before the engine died. He removed the exhaust cam phaser and found a handful of hairline cracks around the oil passages.
Confirmed Repair: The tech replaced the exhaust cam phaser. After the repair, the engine would idle and run smoothly. The problem was resolved.