Idle Speed & Ignition Timing

Ensure idle speed is set to specification. For adjustment procedures, see appropriate ON-VEHICLE ADJUSTMENTS article.

NOTE: Ignition timing is not adjustable on any engine.

On the Wrangler, the engine firing order for the 2.4L 4-cylinder is 1-3-4-2. For the 4.0L 6-cylinder, firing order is 1-5-3-6-2-4, with cylinder No. 1 being the first cylinder from the front of the vehicle in the in-line 6-cylinder engine. For the Liberty, the 2.4L is also 1-3-4-2. The 3.7L 6-cylinder has a firing order of 1-6-5-4-3-2. For the Grand Cherokee, the 4.0L firing order is 1-5-3-6-2-4 and the firing order for the 4.7L V-8 is 1-8-4-3-6-5-7-2.

All ignition timing functions are controlled by the Powertrain Control Module (PCM). Mechanical adjustments are not needed and can't be made. On the 4.0L 6-cylinder engine, do not attempt to rotate the oil pump drive to adjust timing. This adjustment is used for fuel synchronization after camshaft position sensor replacement.