Engine Adjustments Buick Riviera VIII

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. All models use hydraulic lifters. Adjustments are not required.

IGNITION TIMING

Note. All engines are equipped with C(3)I, DIS, IDI or Opti-Spark ignition system. Timing on these systems is not adjustable.

IDLE SPEED & MIXTURE

Note. Idle mixture is controlled by Powertrain Control Module (PCM). Adjustment is not possible.

IDLE SPEED

Note. Idle speed is controlled by PCM and is not adjustable. Slight fluctuations in idle speed are considered normal. Start and run engine for at least 7 minutes to establish PCM control of idle.

Note. Incorrect idle speeds are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.

IDLE MIXTURE

Note. Idle mixture is controlled by Powertrain Control Module (PCM). Adjustment is not required or possible.

THROTTLE POSITION (TP) SENSOR

Note. TP sensor is not adjustable. For further testing procedures, refer to appropriate TESTS W/CODES or SYSTEM/COMPONENT TESTS article.

TP SENSOR LEARN

If a NEW TP sensor, throttle body or PCM is installed, PCM must learn new TP sensor offset. This procedure is necessary because of manufacturing tolerances during minimum air adjustment, TP sensor being non-adjustable on throttle body and TP sensor manufacture. High idle at closed throttle or a stall condition may occur if PCM maintains an improper TP sensor offset. To perform TP sensor learn, turn ignition on leaving engine off. Wait 30 seconds, then turn ignition switch to LOCK position. Wait another 30 seconds.

TP SENSOR ADJUSTMENT VOLTAGE