Missing In Action! 5.7L Hemi Misfire/Won't Idle. (2021 Ram)
Diagnosis of a 2021 Ram 5.7L with a dead miss. The misfire is bad enough that the engine surges and won't idle without applying throttle.
When the scanner is hooked up, it shows the misfire to be on cylinder one with the misfire counter counting up steadily. When Jordan cranks the engine while in clear flood mode, the engine produces a "galloping" sound due to the starter spinning quicker for a fraction of a second due to lack of compression in one cylinder.
Obviously, cylinder one is suffering from a loss of compression, but what's the cause? A vacuum transducer is installer on the vacuum hose for the brake booster in conjunction with a current clamp on the battery positive to observe what's going on on the intake side. Before cranking, the fuel pump fuse was removed rather than using clear flood mode in order to keep the throttle plate closed to produce a better vacuum trace.
Watching the current trace indicates a lower current draw every eighth stroke, visually indicating the low compression on one cylinder. The vacuum trace showed a spike every time the starter current dropped, showing a possible intake valve problem.
When Jordan added a third trace showing the compression on cylinder one, it can be seen that there is not only low compression, but NO compression!
When the engine is started, the scope is configured to show three things. Ignition operation on cylinder one, cylinder pressure, and manifold vacuum. By zooming in on the pattern, we can see where the vacuum breaks, indicating exhaust valve closure.
Watch to the end as we discover what's going on with this fairly new and relatively low mileage (107,000 km) engine.
All of the test equipment used in this video can be purchased at www.autotesttools.com
Don't forget to follow us on
Facebook: / autoaidetechnicalservices
Instagram: / autoaide
Website: http://www.autoaide.ca
Twitter: @autoaidetech
Follow this link to be added to our email to receive the latest news and webinar information
https://form.jotform.com/201346646227252
#hemi #misfire #oscilloscope #ram #scope #pressuretransducer #autotesttools #autoaide #diagnostics #vehiclediagnostics #diagnosticservices #technicaltraining #automotivetraining #diagnostictools #testtools #technicalservices #autel #pico #picoscope #trainingvideos