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.