'81 240 failed emissions test--barely...

I did some searching at brickboard.com and found that there's a mixture adjustment on the injection system, just like the one my '79 Audi 5000 had. I'll be tweaking it in the morning and revisiting the emissions shop. KennyH

Horsepower is cheaper than therapy.

It would help to know where you are, as that may affect the type of fuel system you have, and the allowable emissions levels.

In the UK you should be allowed something like 3.5% CO on an engine of that age (and 1200 ppm HC).

A vacuum leak on its own won't make the mixture richer - what else to look for partly depends upon what fuel system you have, but make sure that the ignition system is OK, plugs are good, air filter clean, etc.

OK. If it is Bosch K-Jet, or one of its varients, then take it slowly (a quarter turn or less at a time), and *count* the turns so that you can restore it to the start point.

It is possible to adjust the mixture reasonably accurately by ear, but if you are not experienced at doing it, an exhaust gas analyser would help a great deal.

This morning before I took it to get retested, I checked the timing, then I turned the mixture adjustment leaner, which decreases idle speed, which I then increases with the idle adjustment knob. I went as lean as I could with the engine still running smoothly.

Presto, it passed with flying colors. CO was 1.94, now it's .54. Big difference. Thanks for the advice! KennyH

Horsepower is cheaper than therapy.

You may have to go back a bit the other way if you have problems with stalling right after a cold start.

None of my cold-start stuff is working, so you may be right. I know the air bypass valve is closed all the time, and I assume the enrichment circuit is also bad, as it's hard to keep running for a minute or two.

I still can't believe the thing idles so well with 282K on it. Next project: Rear bushings. KennyH

Horsepower is cheaper than therapy.