Checking levels of polluting emissions

If idle speed is not 850±30/min, because injection-ignition ECU is self-regulating, the adjustment cannot be carried out. The position of the accelerator linkage must therefore be checked and then the fault detected by means of full diagnosis using a Fiat/Lancia Tester.

CHECKING LEVELS OF POLLUTING EMISSIONS

Foreword

Because the G.M. system is self-adaptive and ensures continual control of idle speed and CO level, no external regulation is necessary (adjustment screws are no longer fitted). A check on exhaust emissions upstream and downstream from the catalytic converter can nevertheless provide valuable information on the condition of the injection-ignition system and engine or catalytic converter parameters.

Checking idling CO and HC levels upstream of catalytic converter

To check the levels of carbon monoxide (CO) and uncombusted hydrocarbons (HC) upstream of the converter, proceed as follows:

1. Unscrew the plug or nut located on the exhaust pipe upstream of the converter and tighten the tool in its place.
2. Connect the probe of a specially calibrated CO-tester in its place.
3. Start up the engine and allow to warm up.
4. Check that the rpm is as specified.
5. Check that idling CO level is as specified (see table); otherwise check:

• Lambda probe operation, using a Fiat/Lancia Tester;
• for air leaks in the area around the Lambda probe seat;
• the injection system (particularly the condition of the spark plugs).

6. Check, under the same conditions, that HC level is lower than 500 p.p.m.
7. If these level are not as specified, adjust the engine and check the following in particular:

• ignition advance angle
• valve clearance
• timing
• engine compression