Fiat 1996 Brava Service Manual page 469

Bravo-Brava @i i* Engine
'98 range Fuel system
10.
CHECKING ENGINE IDLE SPEED
If the engine idle speed is not 850 ± 50 rpm, and as the fuel injection-ignition is self adjusting, no ad­
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.
CHECKING CONCENTRATION OF POLLUTING 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 (especially the state of wear of the spark plugs).
6. Check under the same conditions that the HC concentration is below 600 p.p.m.
7. If these values are not found, tune the engine, checking the following in particular:
- ignition advance;
- valve clearances;
- timing;
- engine compression.
Table of tolerances for polluting emissions
Upstream of catalyzer
Downstream of catalyzer
CO (%)
0.4 - 1
<0.35
HC (p.p.m.)
600
< 9 0
CO2 (%)
^ 12
^ 13
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