91 240 automatic. New to emissions testing. After owning the 240 for 20 years I am now in the land of smog testing near Atlanta.

Here are the numbers:

25/50 Test

HCppm 127 Reading, 1267 allowed, Pass
CO % 0.56 reading, 0.71 allowed, Pass
NOXppm 2361 reading, 910 allowed, Fail
RPM 1759 reading, 3000 allowed, Max
CO+CO% 15.3 reading, 6.0 allowed, Min

50/15 test

HCppm 71 Reading, 132 allowed, Pass
CO % 0.42 reading, 0.73 allowed, Pass
NOXppm 1636 reading, 1006 allowed, Fail
RPM 16935 reading, 3000 allowed, Max
CO+CO% 15.5 reading, 6.0 allowed, Min

So I failed the NOX pretty badly. The ECM is throwing a 232 code - adjusting fuel system for lean or rich condition at idle.

Still getting the 232 code, and no others, but this is what I have done so far:

Replaced:

Plugs (Bosch Platinum)
Plug Wires
Dizzy Cap
Rotor
Air filter
Flame trap and hose
Oxygen sensor
Oil change with Mann filter and Castrol 10w30
Removed and cleaned throttle body, replaced gasket

I made sure all vacuum lines were in good shape with most clamped (probably overkill). And disconnected the Air Mass Meter as simple test (only one in my ability level) and the idle immediately worsened considerably. Plugged it back in and the idle smoothed out quickly.

I also made sure the flap to the manifold hose is closing properly. Coolant is clean and the temp gauge pegs at a hair under normal and is stable.

The CAT is 3-4 years old with probably 30000 miles on it, purchased from FCP Groton. Everything I read is the CAT seems to be OK based on the test results - the problem is probably a lean mixture.

Any thoughts would be greatly appreciated. I get a free retest and really would prefer to pass and get my Georgia plates!

Thanks!!!!