Beretta L4-121 2.0L (1987)
A slow unstable idle may be caused by a system problem that cannot be overcome by the IAC. "Scan" counts will be above 60 counts, if too low, and
"O" counts, if too high.
If idle is too high, stop engine. Ignition "ON". Ground diagnostic terminal. Wait 30 seconds for IAC to seat, then, disconnect IAC. Unground
diagnostic terminal and start engine. If idle speed is above 800 ±50 rpm, locate and correct vacuum leak.
a. System too lean (High Air/Fuel Ratio)
Idle speed may be too high or too low. Engine speed may vary up and down, disconnecting IAC does not help. May set Code 44.
"Scan" and/or Voltmeter will read an oxygen sensor output less than 300 mv (.3v). Check for low regulated fuel pressure or water in fuel. A lean exhaust,
with an oxygen sensor output fixed above 800 mv (.8v), will be a contaminated sensor, usually silicone. This may also set a Code 45.
b. System too rich (Low Air/Fuel Ratio)
Idle speed too low. "Scan" counts usually above 80. System obviously rich and may exhibit black smoke exhaust.
"Scan" tool and/or Voltmeter will read an oxygen sensor signal fixed above 800 mv (.8v).
Check:
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High fuel pressure
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Injector leaking or sticking
c. Throttle Body - Remove IAC and inspect bore for foreign material or evidence of IAC valve dragging the bore.
d. Refer to "Rough, Unstable, Incorrect Idle, or Stalling" in Symptoms
