SureTrack Community Fix: Unbalanced 4Runner

Real Fixes from Mitchell 1’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is available at no additional cost in our ProDemand product.


Here’s another vehicle with intermittent symptoms that tricky to diagnose. Tested all the usual causes and still not fixed. SureTrack community member boysshop had a Toyota 4Runner in the shop that had intermittent idle and stalling issues. They posed the question to the community, and with the help of fellow community members ericsautomotive, DAG1365 and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2002 Toyota 4Runner SR5 3.4L

Title
Erratic idle, stalling, replaced harmonic balancer.

Complaint
Customer complains that truck has rough idle and stalls at times.

Diagnostic Steps Performed/Parts Replaced
Vehicle has an erratic idle, RPMs fluctuate up and down. Starts fine. Found code P0300 random misfire and P0301 through P0306. While driving down road, vehicle seems fine and seems to have the power it should. At intersections or stops, the vehicle will die out. Changed spark plugs and PCV. No vacuum leaks found. Fuel pressure at 42 psi. Cleaned throttle body. MAF and Coolant sensors indicate fine and within specs.

Cause
Found harmonic balancer spinning freely. Woodruff key had broken off and pulley spinning on crankshaft. Thank you for your help!

Correction
Replaced harmonic balancer, road tested vehicle and no longer has rough idle or stalling.


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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.