Fellow Bricksters,
I have been watching this board for awhile and I've learned a great deal from it. What a great resource! I'm the proud owner of a 1984 240 GL with 188k miles. The car looks nearly new and runs great. Except according to the state of Maryland. They seem to think that it emits too much NOX. The readings for HC and CO were excellent. It seems to me that the car must be running too lean. I've found a few leaking vacuum lines, and gave Sponge Bob (square car) a shot of BG 44k cleaner. After an Italian tune up on the highway, the previous hesitation was gone and power was up. Yesterday my wife took him in for another emissions check and he failed NOX miserably. I should mention that we have to run 91 octane or we get knocking. I was going to remove and check the knock sesnsor, but holy cats, it's buried!

A good friend who is a Mercedes mechanic (OK I admit to having a Mercedes 240d also) and has owned Volvos suggested a number of things. I have checked the O2 sensor, but my meter isn't fast enough, though I did get movement. One thing he wan't sure of was whether the 1984 240 had a 2-way catalyst (non-NOX) or a three way. Maybe it's just a bad cat? Recently, I've noticed a rattle in the exhaust that I can't find - broken cat? That would be easiest I think. Is it possible to bolt on a new cat without much cursing a bleeding? If the 84 has a 2 way cat, can a 3 way cat be installed to clean up NOX?

I can't put alot more money into Sponge Bob. Any suggestions? I'm thinking O2 sensor and cat. Maybe a timing change could get me to pass? Any help appreciated!

Current readings:

HC= .7968 Standard is 1.8 GPM
CO= .7212 Standard is 30 GPM
NOX= 4.4220 Standard is 2.8
CO2 =342.7 GPM. No standard