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Home >> Plymouth >> 1972 >> Cricket 1.5L Eng VIN G, Not Available Trans >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> ROOTES Group Twin Carburetor Engine Modification >> Service Procedures >> Setting Idle Speed

Setting Idle Speed

NOTE: Adjustments must be made with engine running. If equipped with air conditioning, compressor must be operating.

To set idle speed, proceed as follows, setting idle speed to specifications below with manual transmission in neutral or automatic transmission in drive.

Model  Idle Man. 
RPM Trans. 
Auto. Trans. 
1970 950 750
1972-73 700 700
Model  Air/Fuel Ratio  Idle CO% 
1970 11.4:1 7.5
1972-73   2.5-4.5
  1. If idle speed is abnormally high and cannot be reduced by adjustment of throttle stop screws, malfunction of by-pass valve is indicated. Refer to THROTTLE BY-PASS VALVE  before proceeding with idle adjustments.
  2. Normal adjustments are made by turning both throttle screws equal amounts, however, most likely cause of poor idling is unbalance between throttles.
  3. Check throttle synchronization by removing air cleaner and check air flow through each carburetor using a suitable balance meter.
  4. When throttles are balanced and idle speed is correct, a rough idle indicates a rich mixture. Using a CO or air/fuel ratio meter, check that CO or air/fuel ratio is as specified. For further information and overhaul procedures see STROMBERG CDSE AND CDSEV in CARBURETOR Section  .