I recently did a smog test and failed. The first time it read. At 15mph NO (PPM) - 1151 and at 25mph 1136. Failing at the 25mph speed test. Then I bought a brand new catalytic converter and got it tested again and this time at 15mph test NO(PPM)- 1529 and at 25mph 895. So it failed for high NO at 15mph speed test. I took the car to a mechanic and he said that its probably something with the egr. But the egr was tested and seemed to work. Also coolant is coming out of the coolant reservoir. Can it be a thermostat problem that cause the smog fail? The car does have a clicking sound when you step on the gas. Maybe clogged injectors so not all cylinders running properly? Any suggestions of what it might be?

If you are blowing coolant out of the reservoir and the car has not been overheating, the radiator cap could be bad. Or, you could be blowing past the head gasket and into the coolant, and that would also account for an emissions problem. I'd suggest checking that out before anything else because a blown head gasket is a major issue.

K thanks I'll look into that.