replaced 02 sensor, MAF swap, idle motor swap, new plugs, cleaned air injector valve, visually checked vaccuum lines, including elbow on firewall. Barely passes HC and NOX. But above code keeps coming up. Smog Tech back flushed injectors and intake manifold via vaccuum line, car runs great. any suggestions? Does the volvo dealer have better diagnostic software than local volvo mechanic? thanks, mel
this may sound too simple, but did you clean/replace the air filter?
If the CO passes and HC is high, check for vacuum leaks around the manifold, check the coolant temperature sender output for continuity through the operating temperature range, check that there are no vacuum leaks in any hose on the engine side of the MAF. Recheck the cam timing.
NOx is purely a function of burn temperature which is effcted by ignition timing and EGR control. No adjustment or correction available as long as the knock sensors are intact and functioning. Make sure the EGR passages are clear and the valve is operating. Use high test gas for the test if you're not usuing it already to keep the timing from adjusting from knock sensor input. Otherwise a catalytic converter is in order.
Bob
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.