failed emissions on nox by .11 % what could i do to make up this small amount. its an 84 244 auto 2.3 n/a car

If you failed for NOx (running lean)then you can retard your timing slightly. I did this (it ran richer - like crap actually) then it passed. I reset timing when I got home.
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Happy Motoring Miguel '86 244 and '87 245

Before you think about replacing your cat, check for vacuum leaks, especially at the intake hose and intake manifold. I failed last week for high NOX. Found a hole in the plastic intake and the intake manifold nuts were slightly more than finger tight. Also check the air box thermostat. The one on my 88 245 with 200k was shot and letting in hot air. I did those three things and passed no problem.

Hello,

Easy. Italian tune-up time. Fresh tank of the highest octane gas you can get plus a bottle of fuel system cleaner. Your local auto supply store might even sell cans of that "guaranteed to pass" stuff. Then drive the crap out of your car for that tank.

An engine that is too cold or one that is too hot will cause it to run out of spec. As to the effect of that emissions, I know that the shop that does mine puts a big giant fan in front of the car when they test to simulate air flow while driving.

Happy Bricking!!!
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Richard - '87 245 DL , '82 242 GLT - Half a million km between them!!!

I'm suffering the same dilemma. I called the local Volvo shop, and he explained the emissions test results to me. Mine failed for HC output and NOx output. HC is Hydrocarbons, basically unburned fuel. NOx is a gas that is only really produced when the engine runs hotter. I believe he said when the combustion chamber exceeds an average temp of 2500 degrees F. He also said it would be $115 for them to check it out. I've changed my sparkplugs, removed and cleaned the throttle-body (with carb cleaner and a shop towel). Run a bottle of fuel injector treatment through it, and premium fuel. And given her an oil change and a new harmonic balancer.

However, from my research into further solutions, there is a rebreather hose at the bottom passenger side of the B230 engine, which can cause your emissions to increase if it's disconnected. That's reconnected now. Also, I was told to check the O2 sensor, and catalytic converter.

As for high NOx readings being caused by hotter engines, I don't know if this is true, but my car did overheat in the inspection bay, to the point of boiling over. I thought nothing of it, as the inspection tech had parked it with the nose literally against the closed bay door, but how likely is it that my thermostat has crapped out?

I feel like I'm chasing gremlins with the smallest cartoonish mallot available.
Aaron Casper
1989 240 DL Wagon.