Hi All,

My 85 245 with an AW70 just barely passed CT emission. The NOX came within a few points of not passing. CO and HC passed easily. Also, the car is getting about 17 MPG of mostly in-town driving with a little highway driving. Are they related? What could be the cause? Thank you - George

George I just re-read your post - forgot to address the poor mileage.

The lean condition I mentioned in my first reply can also be responsible for poor overall performance, which means you end up using more throttle - bad for economy. I think your brick probably needs the full plugs - wires - distributor cap & rotor - air filter - fuel filter treatment; check the flame trap AND the vacuum lines attached to it. Check ALL vacuum lines under the hood, including the long one which goes to the ignition brain box on the right fender (behind the headlight). I suspect that the full treatment (PLUS check that idle mixture!) will restore performance and fuel economy substantially.

This summer I picked up a really clean '92 245 which had been well maintained, but I was puzzled by an intermittent miss or stumble under acceleration. I envisioned fuel pump problems or even more expensive things... but it turned out that the ignition wires were really shot. They worked well enough to start and run the car, but under the increased load of acceleration/high revs they broke down. Got a whole box full of tuneup parts from Foreign Car Parts of Groton for a great price (forget Volvo, this was cheaper than the local parts emporium). With the whole ensemble in place, my 'new' brick no longer stumbled and gas mileage went from 24-25 overall to 28 mpg! (It's a 5-speed, so it does better on gas than the automatic.)

George, a co-worker's '87 245 flunked CT emissions on high NOx. NOx is formed from a too-high combustion temperature, all other things being normal. Looking at the report showed that CO was way down, indicating a too-lean mixture, which drives combustion temps up. I found similar events here by searching the archives, as well as the method of adjusting the idle mixture with a home-made LED instrument.

Any condition which results in running too lean will drive up NOx. As another response indicated, check for vacuum leaks. While you're under the hood check your ignition system components, and disconnect that silver hose which runs from the exhaust manifold to the air filter box (you'll never miss it and your air mass meter will thank you).

Meanwhile, my friend retarded the timing a few degrees and got the car to pass, which means he's good for 2 years. Cheesy way out but desparate men do desparate things!

In my friend's cars with the B230 the high NOX was caused by a bad cat. His
mileage didn't go up a lot though. It went up a mpg or so. His car is usually
getting 20-25 mpg though.

You may have couple of problems. I suggest you inspect the motor carefully for vacuum leaks. Fix all that you find. Check all the basics like the plug wires, cat rotor, etc. The plug wires can be sneaky. They will look OK but they'll have corrosion where they attach to the plugs. The coil wire likes to short to things
also. After all the basics then suspect things like the AMM. Hope this helps.
Dave 82 242ti 262k mi.