So for those that remember we went rounds last year with the emissions on Jonah's 76. In the end they decided it needed to be tested as an 85 due to the EFI engine. We added a cat and ended up passing. Still unhappy about the later model testing standards.
One year later we run it through. This year no questions on the engine, no notes in the computer and they test it as a 76, Great! but we fail miserably. HC is 2000, limit is 600. CO is around 7, limit is 2.
We hooked up a code reader and got a defective PCV valve, and lean readings on the O2 sensors. That was it.
We swapped in a different PCV, retarded the timing a bit, put on a new air filter (it was dirty), did a compression check (around 125 on all cylinders), and did the denatured alcohol trick.
We did pass the retest -
HC 401 (idle), 317 (2500 rpm), limit is 600
CO 0.48 (idle), 1.24 (2500 rpm), limit is 2.00

Passed , but still something wrong. Anyone have any ideas. Engine is an 89 from a Grand Marquis, speed density. stock harness.

Your issue is you live in the wrong county...LOL!

Beyond that I am not much help.

ccb