Checking Concentration Of Polluting Emissions; Checking Co And Hc Concentration During Idling Upstream Of The Catalytic Converter; Table Of Tolerances For Polluting Emissions; Checking Engine Idle Speed - Fiat Bravo Service Manual

Bravo-Brava ft **
'98 range
C H E C K I N G E N G I N E I D L E S P E E D
If the engine idle speed is not 850 ± 50 rpm, and as the fuel injection-ignition is self adjusting, no a d -
justments can be made, so it is not necessary to check the correct adjustment of the throttle linkage.
Faults should therefore be sought by means of full diagnosis using the Fiat/Lancia Tester.
C H E C K I N G C O N C E N T R A T I O N O F P O L L U T I N G E M I S S I O N S
Via the self-adaptivity of the system, the fuel injection-ignition ensures continuous control of the idle
speed and CO level, thus rendering any external adjustment unnecessary (there are no adjustment
screws). However, a relative check on the contents of the exhaust gases upstream and downstream of
the catalytic converter can give useful information on the operating conditions of the fuel injection-igni-
tion, the engine parameters or the catalytic converter.

Checking CO and HC concentration during idling upstream of the catalytic converter

To check the concentrations of carbon monoxide (CO) and unburnt hydrocarbons (HC) upstream of
the catalytic converter, proceed as follows:
1. Undo the plug or nut located on the exhaust pipe, upstream of the catalytic converter, and screw in
the tool.
2. Connect the probe of a suitably calibrated CO tester to the tool.
3. Start the engine and bring it up to temperature.
4. Check that the rpm is correct.
5. Check that the CO concentration during idling is as specified in the table below; if not, check:
- the correct operation of the Lambda probe using the Fiat/Lancia Tester;
- the presence of air leaks in the area surrounding the Lambda probe seating;
- the fuel injection and ignition system ( e s p e c i a l l y t h e s t a t e of w e a r of the s p a r k p l u g s ) .
6. Check under the same conditions that the HC concentration is below 600 p.p.m.
7. If these values are not f o u n d , tune the engine, checking the following in particular:
- ignition advance;
- valve clearances;
- timing;
- engine compression.
T a b l e of t o l e r a n c e s for polluting e m i s s i o n s
Upstream of catalyzer
Downstream of catalyzer
Copyright Fiat Auto
HC (p.p.m.)
CO (%)
0.4 - 1
< 0 . 3 5
E n g i n e
Fuel system
CO2 (%)
^ 12
600
^ 9 0 5s 13
10.
57