Another CA Smog Question w/ Smog Report

[RCM3]

Failed smog due to high NOx emissions. Everything else on the test is far below what the average passing car emits. Just hoping to get some advice before I start replacing things.

Background on the car: 224k. Top end rebuild done last year, so new plugs, vacuum lines, etc. I did not replace the plug wires or the cap and rotor however. From the reading I've done here it seems the cat should be replaced as a last resort as its the original cat and that high NOx emission are caused from high combustion temperatures only. Any advice on where to go next?

Here are the two failed emission reports. I went back for a re-test thinking I didn't warm the car up sufficiently the first time, or maybe some gas additive was still in my gas at the time of the first test. The test report on top is the second test also.



Any help is greatly appreciated guys, thanks!


-Ryan

[jlevie]

Either the engine is running lean above idle or the catalytic converters are bad. With HC and CO both very low a lean condition seems likely. Intake leaks, rail fuel pressure, injectors, ECT sensor, AFM, or even the DME could be causes. You can verify the lean condition by looking at the plugs.

[RCM3]

Either the engine is running lean above idle or the catalytic converters are bad. With HC and CO both very low a lean condition seems likely. Intake leaks, rail fuel pressure, injectors, ECT sensor, AFM, or even the DME could be causes. You can verify the lean condition by looking at the plugs.

Thank you! Going to start going down that list now.

[RCM3]

Ok, car passed smog today. Just wanted to update the thread with why it failed originally. Upon rebuilding the top end, I tweaked the coupling on the manifold pictured below. This allowed exhaust vent out before the O2 sensor, causing the car to run lean. Fixed the gap in the exhaust and it passed no problem.

Again thanks for the advice.