SureTrack Community Fix: Misfire Woes
Real Fixes from ShopKey’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 currently available free with the purchase of a current Snap-on® diagnostic software version or in our ShopKey Pro product.
Misfires are a common problem with many causes. SureTrack community member BIGFOS75 had a 2009 Chevy Tahoe in the shop for a misfire concern and all the usual causes were not to blame. They posed the question to the community, and with the help of fellow community member nate75 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.
2009 Chevrolet Tahoe 4.8L
Miss on Cylinder 4, replaced lifter.
Customer complains of misfire in engine.
Diagnostic Steps Performed/Parts Replaced
Ran engine and found missfire on cylinder number 4. Checked compression and it is at 120 with no leak down. Swapped coil plug wire and injector to no avail. Getting good strong spark. Getting NOID and injector leak down is ok. Checked with scan tool for vacuum leaks and intake and none found. What am I missing?
Best Answer from Community Member nate75
Try a running compression test and compare with a known good cylinder. Should be no more than 5 PSI difference. Check for proper rocker arm travel, could be a worn camshaft. Many times, worn cam lobes/valvetrain issues don’t show up on a static compression test.
Had worn lifter roller, camshaft was ok.
Replaced lifter and issue is resolved.
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