Engine hesitation

PETERP0418

MEMBER
2012 TOYOTA TUNDRA
4.6L
V8
4WD
AUTOMATIC
58,800 MILES

The check engine light came on and I ignored it for a few days since I do not drive between twelve to forty miles per day.
I borrowed a meter and got the P0418 code for secondary air injection system system relay 'A' circuit malfunction permanent failure.
I read up about this code thinking it was not a big issue since the vehicle was running normal. As days passed the vehicle would not accelerate very well even though the engine seemed to sound normal and rev up when I stepped on the gas pedal.
The problem continued to get worse and I feared to drive it.
I drove it to a local shop and had the transmission serviced. That did not solve the problem.
I finally drove it to a Toyota service department and they replaced the two air pump assemblies, two emission valve sets, air pump inlet, gaskets and clips for free under extended warranty. Great service from Toyota.
To me it was a transfer of power issue verses engine hesitation.
I hope you could help clarify the difference.
Thank you.

2 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Your perception of the problem was accurate. It seemed to have a loss of power even though the engine sounded okay. The air injection plays an important role and its failure can lead to several problems. First, the air pump is part of the secondary injection system. Basically, it pumps air into the exhaust to help produce a cleaner burn before exhaust is emitted into the atmosphere. If it fails, it can tune of the vehicle, which will impact overall engine performance. A bad pump can cause the engine to hesitate, stumble on acceleration, and in some cased, cause a noticeable loss of power. It sounds like that is what was happening. The loss of power seemed like a power transfer issue to you.