Low Idle After Alternator Swap - Loose Belt and Low Battery

Electricalbeginner✓ OP Confirmed

Problem

After swapping the alternator on an MKIII Supra, the engine idled low and had hesitation when accelerating. The alternator belt was also squeaking.

Low idle after alternator swapHesitation when pressing throttleAlternator belt squeakingIdle well below normal 650 RPM

Root Cause

Two contributing factors: (1) The alternator belt was not tightened sufficiently after the swap, causing slipping and hesitation. (2) The battery was low/depleted from driving on the failed alternator, which caused weak spark and low RPM until the new alternator had time to recharge it.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted September 2011 on SupraForums.com