I found a Microsoft Word document on a website somewhere (I believe it was a dealer or some repair organization). I'd like to give credit where it is due, but I can't recall where I found it. I haven't used it yet, but I intend to some day. Let me know how it works out if you try it. Some of the values in parentheses ( ) are my changes. The doc has a diagram at the bottom, which I've replaced with a description.



Setting Your Base Engine Idle Specs
on cars with LH- 2.1 and 2.2 Jetronic fuel injection


Many driveability and running problems can be traced to improper base engine settings. Setting your base idle specifications is always the first step when trouble shooting any runability problem. By following the steps below the source of most problems can be identified

1. Check for air leaks by spraying carburetor cleaner on all intake hoses and gaskets. Any fluctuation in idle while an area is being sprayed means a leak. Repair any leaks you find. Don’t spray carburetor cleaner on hot manifolds as it may cause a fire.
2. Remove and clean the throttle body, adjust the throttle plate open ¼ turn. Reinstall it using new gaskets. Make sure the throttle switch clicks as soon as you crack the throttle (adjust as needed).
3. Start your engine and let it warm up fully.
4. Set ignition timing to the manufacturer’s specs.
5. Now use a voltmeter to verify that your 02 sensor is working properly. Connect the red probe from the voltmeter to the 02 sensor wire where it is connected to the large green wire. Connect the black probe from the voltmeter to ground. A good 02 sensor will fluctuate between .2 and .7 volts if your mixture is anywhere close. Replace the 02 sensor if needed.
6. Go to the right inner fender well (740’s) or the left inner fender well (240’s) and find the red and white pigtail (blue and white) that sits besides the ignition ECU. This is your CIS test point. Ground this connector and adjust the bypass air thumbscrew on the throttle body until the idle is 725 RPM’s (700). Remove the ground from your test point; the idle should be close to 750 RPM’s (+/- 20).
7. Next to the red and white wire (blue and white) is a green and white pigtail (pink). This is your CO test point. Using Volvo special tool part #9995280 (approx. $35) plug one end of the test LED to the fender well connector and the red connector to the positive terminal of the battery. A logic probe can be used in place of the Volvo special tool or if you are handy build the circuit below. Remove the tamper proof plug from the air mass meter by drilling two 1/8” holes in the plug about 3/16” deep and removing the plug with needle nose pliers or snap ring pliers. This will reveal the CO adjusting screw. Adjust the AMM until the LED on the tester blinks on and off at equal intervals.

Congratulations! You have just set your engine’s base idle specs.

Note: when the tester LED is off it represents a lean mixture, when it is on the mixture is rich.


****Homemade tester

Wire a 750 ohm resistor in series with an LED. Connect one end to the battery positive terminal, and the other end to the CO test point described above (green and white, or pink). (Make sure the positive end of the diode is towards the battery end, and the negative end is towards the test point).