What are a few tips you all can give for passing the emissions test? I know that you need to have that aluminum hose on, but thats all I know at the moment. What else is there that I should be aware of before driving into xyz service station to get my volvo legal ?

cheap and easy--my 240 had high NO on its first try, and after reading brickboard I put in a bottle of injector cleaner and tried again. Problem solved
-Kurt

The degree of how stringent the test depends a lot on what state and region you are in. My two 240's are veterans of VA and CA emissions testing, among the toughest. For these two states, each has two sets of passing requirements, one more difficult for states' high traffic density regions (e.g. LA County and Northern Virginia). The tougher test requires a 15 and 25 mph dyno "load" on the car and includes NOX and well as CO and HC. The easier test is for non-urban areas, tests for CO and HC only (no NOX) at Idle RPM and 2500 rpm w/no dyno load.

In general however, prep your car as best you can:

New filters
Recent complete ignition tune up
Operating O2 sensor
Operating Catalytic Converter

Many 240s suffer from intake vacuum leaks which will drive up the NOX number and also may cause the O2 sensor to overcompensate and affect the HC and CO numbers. Most common source of vacuum leaks are fuel injector seals and cracked, broken or disconnected rubber vacuum lines.

If CAT is not good, there is no way the car will pass.

You are right, pre-heat hose needs to be intact and air box thermostat needs to work, or at least be in the open (not pre-heated) position. Emissions test also includes fuel tank cap test; make sure it has a good seal. Your PCV (flame trap) system should be maintained.

All above from my own experiences. Many shops offer a pretest service so you can determine what shape your car is in.

Good luck

Robert
84 245Ti
88 245DL

In addition, make sure your car has had a good run before you take it in for testing and make sure you get it in the shop while it's still at operating temperature. I have heard of people leaving their car on the garage parking lot and the mechanic doing the tests with the engine cooler than normal operating range - higher emissions are produced by a cold engine. The Catalytic (sp?) converter is also less efficient when cold.

Another reason to run it hard before testing is that if your car is burning any oil, and you do a lot of short distance or stop-and-go driving, residue will accumulate in the exhaust system and be burned off slowly. If you get it hot this residue will be burned off before emissions testing and will help to lower readings.

Kevin - 1980 242GT