Here are the symptoms:
- Check Engine Light on.
- Slight Hesitation when accelerating from a dead stop.
- There's a ticking sound coming from somewhere near/underneath the air cleaner. Only happens when truck is moving, and is intermittent. This sound happened all the time before the replacement of the EVAP Solenoid and Idle Valve Assy... now it rarely happens, but still does once in a while.
Emission Test Result: Everything passed good with the exception of the
NO(PPM) @15 MPH 1993 (max allowable 539) @25 MPH 1816 (max allowable 792)
I took the Emission test when my check engine light mysteriously turned itself off.
Repairs I've had done (before the smog test): Replaced cracked exhaust manifold. Replaced AAC Valve Assy, Idle Air and the EVAP Solenoid.
The repairs were done in response to the following codes found in the computer: PO304 & PO402. There was at least on other code, but I forgot what it was :-( I want to say P442, but I'm really not sure.
Any idea on what could be causing the really high NO readings and the check engine light?