ENGINE MECHANICAL
Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
VALVE CLEARANCE
Note. All engines use hydraulic lifters or lash adjusters. No adjustments are required.
IGNITION TIMING
On all models, ignition timing is controlled by Powertrain Control Module (PCM) and is nonadjustable. For diagnosing PCM, see appropriate SELF-DIAGNOSTICS article.
IDLE SPEED & MIXTURE
On all models, idle speed and mixture are controlled by Powertrain Control Module (PCM). No adjustment is required. The PCM controls Idle Air Control (IAC) motor for proper idle speed. For diagnosis, see appropriate SELF-DIAGNOSTICS article.
THROTTLE POSITION SENSOR
On all models, Throttle Position (TP) sensor is nonadjustable. DO NOT attempt to adjust TP sensor by rotating. Output voltage (center terminal of TP sensor) should be approximately .8 volt at closed throttle (idle) and more than 3.5 volts at Wide Open Throttle (WOT). Voltage should increase gradually and smoothly as throttle is slowly opened from idle to WOT. TP sensor must be replaced if it is out of range. For diagnosing TP sensor circuits, see appropriate SELF-DIAGNOSTICS article.