Good morning!

I was hoping to get some help and guidance with an emissions problem. The basic problem: at my last inspection the emissions teste high across the board - HC, NOx, CO - and I'm not sure why. Unfortunately, I wasn't given a copy of the values. I was just told that at all were high and at least one was "off the scale". They also reported back that the OBD showed codes, but they didn't know what they meant. Oh yeah, and they cleared the codes AND didn't record them, so I'm out of luck there too.

I went obvious with an obvious solution and checked the O2 sensor. It's voltages come back normal per the FAQ. I'm not quite sure what the check out next. Perhaps the most confounding part of this is my mileage - it doesn't seem to be suffering. My last fill-up after "mostly highway" driving yielded 20.6 mpg, which, at least historically for this car, is about right.

Here's some history:
- The car's only got 146k miles.

- Prior to last year's emissions check the car had spent 6 years in states without emissions checks, so earlier versions or iterations of this problem might have been around for a while without my knowing it.

- The exhaust stinks pretty bad, as might be expected.

- The car failed last year's emissions inspection as well, but that was corrected by replacing the O2 sensor. For that problem, I actually have the numbers:
Old New
HC 181 24ppm
CO2 13.7 13.8%
NO 113 8ppm
CO 0.54 0.02%
O2 1.0 3.4%

- I replaced the catalytic converter around 5 years (20k miles) ago. At the time it seemed like a good idea since the original looked like it was rusting thru.

- In case it's important, the resonator currently needs to be replaced in a bad way - it's what's left of the original.

- No significant codes have reproduced. The only code I've seen is "low battery voltage", which isn't surprising to me since the battery has been discharging if the car sits unused for more than 2-3 weeks. I'm assuming there's a 'small' short somewhere that I'll need to track down eventually.

- The car has overheated twice in its life. First time was around 9-10 years ago. Thermostat went bad. Second overheat was last summer (between the two inspections mentioned here). In that case the top ferrule on the radiator gave up on me and cracked off.

- Four of the 6 ignition coils were replaced about 15k miles ago (I forget the cause/effect that led to this...)

- IAC replaced ~20k miles ago.

- Intake manifold gasket replace 15-20k miles ago (original was pretty much disintegrated).

- Replaced the spark plugs 14 months (about 1000 miles) ago.

Any help and guidance to troubleshooting this problem would be greatly appreciated.

Thanks!
-John